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Resume Contexte Les troubles du spectre du placenta accreta (TSPA) constituent une complication de la grossesse potentiellement mortelle et exigent une coordination des soins interdisciplinaires afin d'ameliorer la possibilite d'une issue favorable. La hausse de la frequence des cas est due a l'augmentation du nombre d'interventions chirurgicales uterines, notamment a l'augmentation de la frequence des grossesses apres cesarienne. Objectif Fournir des directives cliniques factuelles courantes sur les methodes optimales pour depister, diagnostiquer et prendre en charge les TSPA de facon efficace. Methode Les membres du comite sur les directives cliniques ont ete selectionnes en fonction de leur milieu de pratique et de leur expertise actuelle en matiere de prise en charge de cette maladie au Canada. Le comite a revu toutes les donnees probantes disponibles dans la litterature medicale en anglais, y compris des lignes directrices publiees ainsi que des tests de diagnostic, des interventions chirurgicales et les issues cliniques evaluees. Donnees probantes La litterature publiee jusqu'en mars 2018, y compris les directives cliniques, a ete puisee dans les bases de donnees Medline et Cochrane Library au moyen d'un vocabulaire controle et de mots cles. Les resultats sont limites aux analyses systematiques, aux essais cliniques randomises et aux etudes observationnelles rediges en anglais. Les recherches ont ete mises a jour regulierement, et les resultats ont ete incorpores a la directive clinique jusqu'en juillet 2018. Criteres La qualite des donnees probantes dans le present document a ete evaluee en fonction des criteres decrits dans le rapport du Groupe d'etude canadien sur les soins de sante preventifs. Resultats Le present document passe en revue les donnees probantes relatives aux techniques diagnostiques et chirurgicales utilisees pour favoriser la prise en charge optimale des femmes chez qui l'on suspecte un TSPA, notamment l'anesthesie et les considerations cliniques de la prestation de soins interdisciplinaires. Avantages, prejudices et couts La mise en application des recommandations de la presente directive clinique ameliorera la sensibilisation a cette maladie et augmentera la proportion des femmes atteintes recevant des soins interdisciplinaires dans des centres regionaux. Conclusion La prestation de soins par une equipe interdisciplinaire qui assure de bons services diagnostiques, la planification concertee et les interventions chirurgicales securitaires fournissent des soins qui ameliorent les issues cliniques comparativement aux autres modes de prise en charge. DECLARATIONS SOMMAIRES 1La frequence des troubles du spectre du placenta accreta est en hausse constante dans de nombreux pays, vraisemblablement en raison de l'augmentation de la proportion de femmes qui deviennent enceintes apres avoir subi une ou plusieurs interventions chirurgicales uterines, notamment des cesariennes multiples. 2Les troubles du spectre du placenta accreta dans un contexte d'antecedents de cesarienne decoulent de l'implantation de la grossesse dans la niche au niveau de la cicatrice pres de la jonction cervico-isthmique de l'uterus. Diverses methodes echographiques permettent de diagnostiquer la manifestation precoce d'une « grossesse sur cicatrice de cesarienne ». 3L'echographie peut servir a depister et a diagnostiquer les grossesses avec un placenta praevia anterieur complique par un trouble du spectre du placenta accreta. L'efficacite de l'echographie dans ce contexte depend de la connaissance des facteurs de risque cliniques, de la qualite de l'imagerie, de l'experience de l'echographiste, de l'âge gestationnel, des modalites d'imagerie et du volume vesical adequat. 4L'imagerie par resonance magnetique peut appuyer l'echographie multimodale dans le diagnostic et la classification des troubles du spectre du placenta accreta; cependant, la contre-indication relative de l'utilisation du gadolinium comme agent de contraste limite actuellement son efficacite. 5Les troubles du spectre du placenta accreta sont potentiellement mortels et necessitent la prestation de soins par une equipe interdisciplinaire regionale afin de maximiser les chances d'issue favorable pour la mere et le nourrisson. RECOMMANDATIONS 1Il y a lieu de diriger les femmes enceintes qui presentent un placenta praevia anterieur et des facteurs de risque cliniques des troubles du spectre placenta accreta a l'echographie obstetricale de 18-20 semaines vers des services d'imagerie specialisee afin de diagnostiquer ou d'exclure cette maladie (II-2A). 2Il y a lieu de diriger les femmes qui ont recu un diagnostic de troubles du spectre du placenta accreta vers un centre regional designe a la prise en charge interdisciplinaire de cette maladie (II-3A). 3Les soins interdisciplinaires rattaches a un protocole qui s'etend du diagnostic a l'intervention chirurgicale optimiseront les issues a la fois peroperatoires et postoperatoires (II-3A). 4L'admission prenatale dans un centre de prise en charge regional designe peut etre indiquee, surtout a la suite d'une hemorragie ante partum, ou en fonction de contraintes geographiques ou de transport (III-B). 5Chez les femmes autrement en sante dont l'historique de grossesse ne comporte aucun saignement vaginal, le meilleur moment pour proceder a la cesarienne planifiee se situe entre 34 et 36 semaines de grossesse (II-3B). Il convient d'envisager d'effectuer l'intervention plus tot en cas d'episodes repetes d'hemorragie ante partum ou de contractions afin de reduire le risque d'intervention chirurgicale d'urgence non planifiee; on doit aussi idealement administrer une corticotherapie pour favoriser la maturation pulmonaire fœtale si l'intervention a lieu avant 35+0 semaines de grossesse (II-2A). 6L'anesthesie regionale peut s'averer plus securitaire que l'anesthesie generale etant donne qu'elle est liee a une perte sanguine moindre et que les patientes et leur partenaire la prefere (II-2A). Un protocole de transfusion massive doit etre en place afin de pouvoir reagir en cas de perte sanguine importante (III-B). 7Il y a lieu d'administrer de l'acide tranexamique par voie intraveineuse au debut de l'intervention parce qu'elle diminue la perte sanguine peroperatoire (I-A). 8Il convient de realiser l'intervention chirurgicale en position de lithotomie modifiee, au moyen d'une incision mediane assez haute pour extraire le fœtus sans pratiquer d'incision dans le placenta; l'echographie pre- ou peroperatoire peut etre utilisee afin de determiner l'incision uterine optimale (III-B). Si le placenta ne montre aucun signe de decollement, il convient de ne pas tenter de l'extirper en raison de l'hemorragie importante qui peut en decouler (III-B). 9A l'heure actuelle, il n'y a pas suffisamment de donnees probantes pour recommander ou non l'administration de medicaments uterotoniques apres l'extraction du fœtus (III-C). 10A l'heure actuelle, il n'y a pas suffisamment de donnees probantes pour recommander une methode ou une autre (insertion preoperatoire de ballonnets ou ligature peroperatoire) visant a reduire le debit sanguin des arteres iliaques internes avant l'hysterectomie (II-1C). 11Une atteinte centrale focale peut se preter a la resection cuneiforme (wedge) avec retrait complet du placenta et reparation de l'uterus (triple-P) (II-3B). 12La cesarienne classique avec abandon du placenta envahissant constitue une methode d'accouchement acceptable, mais elle prolongerait le temps de recuperation et presente un risque persistant d'hysterectomie (II-3B). 13Il convient de recommander aux femmes qui demeurent fertiles apres un diagnostic de trouble du spectre de placenta accreta d'obtenir une echographie aupres d'un specialiste tot dans toute grossesse subsequente de sorte que toutes les options de prise en charge demeurent sur la table en cas de grossesse sur cicatrice de cesarienne (III-B). 14Le diagnostic prenatal des formes les plus graves de troubles du spectre du placenta accreta, designees comme des grossesses sur cicatrice de cesarienne, peut rendre possible une prise en charge au moyen de techniques chirurgicales a effraction minimale (II-3D). 15Bien que bon nombre de femmes presentant un trouble du spectre du placenta accreta recoivent des soins securitaires dans les pays bien outilles, il faut pousser la recherche et favoriser le transfert de connaissances encore davantage pour offrir efficacement toutes les options de prise en charge a la population (III-B).

Background Placenta accreta spectrum (PAS) disorders are a potentially life-threatening complication of pregnancy that demand coordinated interdisciplinary care to achieve safer outcomes. The rising incidence of this disease is due to a growing number of uterine surgical procedures, including the rising incidence of pregnancy following Caesarean section. Objective To provide current evidence-based guidelines on the optimal methods used to effectively screen, diagnose, and manage PAS disorders. Methods Members of the guideline committee were selected on the basis of their ongoing expertise in managing this condition across Canada and by practice setting. The committee reviewed all available evidence in the English medical literature, including published guidelines, and evaluated diagnostic tests, surgical procedures, and clinical outcomes. Evidence Published literature, including clinical practice guidelines, was retrieved through searches of Medline and The Cochrane Library to March 2018 using appropriate controlled vocabulary and key words. Results were restricted to systematic reviews, randomized controlled trials, and observational studies written in English. Searches were updated on a regular basis and incorporated in the guideline to July 2018. Values The quality of evidence in this document was graded using the criteria described in the Report of the Canadian Task Force on Preventive Health Care. Results This document reviews the evidence regarding the available diagnostic and surgical techniques used for optimal management of women with suspected PAS disorders, including anaesthesia and practical considerations for interdisciplinary care. Benefits, Harms, and Costs Implementation of the guideline recommendations will improve awareness of this disease and increase the proportion of affected women receiving interdisciplinary care in regional centres. Conclusions Interdisciplinary team-based care providing accurate diagnostic services, coordinated planning, and safer surgery deliver effective care with improved clinical outcomes in comparison with alternative management. Summary Statements 1The incidence of placenta accreta spectrum disorders is steadily rising in many countries, likely due to the increasing proportion of women becoming pregnant following a variety of surgical procedures to the uterus, including multiple Caesarean sections. 2Placenta accreta spectrum disorders in the setting of prior Caesarean section deliveries arises from pregnancy implantation within the niche created by this surgery near the cervicoisthmic junction of the uterus. This early presentation as a "Caesarean section scar pregnancy" may be diagnosed by ultrasound methods. 3Ultrasound may be used to screen for, and to diagnose, pregnancies with anterior placenta previa that are complicated by placenta accreta spectrum disorders. The effectiveness of ultrasound in this context depends upon awareness of clinical risk factors, imaging quality, operator experience, gestational age, imaging modalities, and adequate bladder filling. 4Magnetic resonance imaging may complement multimodal ultrasound in the diagnosis and staging of placenta accreta spectrum disorders, though its effectiveness is currently limited by the relative contraindication to the use of a gadolinium contrast enhancing agent. 5Placenta accreta spectrum disorders are potentially life-threatening and demand regional interdisciplinary team-based care to deliver the safest outcomes for mothers and infants. Recommendations 1Pregnant women with clinical risk factors for placenta accreta spectrum disorders and anterior placenta previa at the 18–20-week fetal anatomical ultrasound should be referred for specialist imaging to diagnose or exclude this disorder (II-2A). 2Women with a diagnosis of placenta accreta spectrum disorder should be referred to a regional centre dedicated to the interdisciplinary management of this condition (II-3A). 3Protocol-based interdisciplinary care from diagnosis to surgery will optimize both intraoperative and postoperative outcomes (II-3A). 4Antenatal admission to a designated regional management centre may be indicated, especially following an antepartum hemorrhage, or based on considerations of geography or transport conditions (III-B). 5For otherwise healthy women with no history of vaginal bleeding, the optimal timing of elective Caesarean section delivery is around 34–36 weeks gestation (II-3B). Surgery should be considered earlier for repeated episodes of antepartum hemorrhage or contractions to reduce the risks of emergent unplanned surgery and should ideally be preceded by a course of corticosteroids to enhance fetal lung maturation if prior to 35+0 weeks gestation (II-2A). 6Regional anaesthesia may be safer than general anaesthesia as it is associated with reduced blood loss and is preferred by patients and their partners (II-2A). A massive transfusion protocol should be in place to respond to significant blood loss (III-B). 7Intravenous tranexamic acid should be administered at the commencement of surgery because it reduces intraoperative blood loss (I-A). 8Surgery should be performed in the modified lithotomy position, using midline access, sufficiently high so as to deliver the fetus without incising through the placenta; preoperative or intraoperative ultrasound can be used to guide the optimal uterine incision (III-B). No attempt should be made to remove the placenta if it shows no signs of separation as this may cause substantial hemorrhage (III-B). 9Presently there is insufficient evidence to recommend giving or withholding uterotonic drugs after delivery of the fetus (III-C). 10Presently there is insufficient evidence to recommend either approach (preoperative balloon placement or intraoperative ligation) designed to arrest blood flow from the internal iliac arteries prior to hysterectomy (II-1C). 11Focal central disease may be amenable to wedge resection, with complete removal of the placenta and repair of the uterus (the triple-P procedure) (II-3B). 12Classical Caesarean section and non-removal of the invasive placenta is an acceptable method of delivery but is associated with a protracted course of recovery and a persistent risk of hysterectomy (II-3B). 13Women who retain their fertility following a diagnosis of placenta accreta spectrum disorder should be instructed to access specialist ultrasound early in any future pregnancy so that all management options are available should a Caesarean section scar pregnancy be found (III-B). 14Prenatal diagnosis of the more severe forms of placenta accreta spectrum disorder, expressed as a Caesarean section scar pregnancy, may permit management using minimally invasive surgical techniques (II-3B). 15Though many women with placenta accreta spectrum disorder in well-resourced countries receive safe care, more research and knowledge translation are needed to effectively deliver all management options at the population-based level (III-B).

Resume Objectifs Fournir des directives factuelles qui favorisent l'accouchement vaginal assiste securitaire et efficace. Resultats Conditions prealables, indications, contre-indications, ainsi que les morbidites maternelles et neonatales liees a l'accouchement vaginal assiste. Donnees probantes Des recherches ont ete effectuees dans la base de donnees Medline pour trouver des articles publies entre le 1er janvier 1985 et le 28 fevrier 2018 en utilisant les termes anglais suivants : assisted vaginal birth, instrumental vaginal birth, operative vaginal delivery, forceps delivery, vacuum delivery, ventouse delivery. La qualite des donnees probantes indiquees s'appuie sur les criteres d'evaluation des donnees decrits dans le rapport du Groupe d'etude canadien sur les soins de sante preventifs. Validation La presente directive a ete approuvee par le comite de pratique clinique – obstetrique et le conseil d'administration de la Societe des obstetriciens et gynecologues du Canada. RECOMMANDATIONS 1La necessite d'assister un accouchement vaginal peut etre diminuee grâce aux mesures suivantes : soutien dedie et continu durant le travail (I-A), augmentation du travail inadequat par l'administration d'ocytocine (I-A), retarder de la poussee chez les femmes sous peridurale (I-A), augmentation du temps de poussee chez les femmes nullipares sous peridurale (I-B) et optimisation du positionnement de la tete fœtale par rotation manuelle (I-A). 2Le fait de favoriser l'AVA securitaire et efficace aux mains de fournisseurs de soins competents et experimentes peut s'averer une strategie efficace pour diminuer le taux de cesarienne primaire (II-2B). 3Pour qu'un accouchement vaginal assiste s'avere securitaire et efficace, il est necessaire de detenir l'expertise requise avec la methode choisie, d'effectuer une evaluation complete de la situation clinique et de communiquer de facon claire avec la patiente, ses personnes de soutien et le personnel soignant (III-B). 4Les praticiens qui effectuent un accouchement vaginal assiste doivent avoir les connaissances, les competences et l'experience necessaires pour evaluer la situation clinique, utiliser l'instrument choisi et gerer les complications qui peuvent decouler d'un accouchement vaginal assiste (II-2B). 5Les stagiaires en obstetrique devraient recevoir une formation complete sur l'accouchement vaginal assiste; ils doivent egalement etre declares competents avant de pratiquer un accouchement vaginal assiste sans supervision (III-B). 6Lorsque l'on juge que l'accouchement vaginal assiste comporte un risque eleve d'echec, on doit le considerer comme une tentative d'accouchement vaginal assiste et l'effectuer dans un endroit ou il est possible de recourir immediatement a la cesarienne (III-B). 7Le medecin doit choisir l'instrument le mieux adapte aux circonstances cliniques en fonction de son degre de competence. La ventouse et les forceps sont associes a divers risques et avantages a court et a long termes. La ventouse est plus susceptible de conduire a l'echec de l'accouchement que les forceps (I-A). 8Il n'est pas recommande de planifier d'utiliser successivement les instruments puisque cette approche est possiblement liee a un risque accru de trauma perinatal. En cas d'echec d'une tentative d'accouchement avec ventouse, le medecin doit evaluer les risques d'une tentative avec les forceps par rapport a ceux d'une cesarienne (II-2B). 9L'utilisation restreinte de l'episiotomie mediolaterale est indiquee lors d'un accouchement vaginal assiste (II-2B). 10Un retour doit etre effectue avec la patiente et ses personnes de soutien immediatement apres une tentative d'accouchement vaginal assiste, qu'elle soit fructueuse ou non. Si ce n'est pas possible, il faut idealement le faire avant que la patiente n'obtienne son conge et lui faire part des indications pour l'accouchement vaginal assiste, du plan de prise en charge de toute complication et du pronostic pour de futurs accouchements (III-B). 11Les patientes devraient etre encouragees a envisager un accouchement vaginal spontane pour les grossesses subsequentes. Le plan de soins devrait neanmoins etre personnalise et respecter les preferences de la patiente (II-3B).

Objectives To provide evidence-based guidelines for safe and effective assisted vaginal birth. Outcomes Prerequisites, indications, contraindications, along with maternal and neonatal morbidity associated with assisted vaginal birth. Evidence Medline database was searched for articles published from January 1, 1985, to February 28, 2018 using the key words "assisted vaginal birth," "instrumental vaginal birth," "operative vaginal delivery," "forceps delivery," "vacuum delivery," "ventouse delivery." The quality of evidence is described using the Evaluation of Evidence criteria outlined in the Report of the Canadian Task Force on Preventive Health Care. Validation These guidelines were approved by the Clinical Practice Obstetrics Committee and the Board of the Society of Obstetricians and Gynaecologists of Canada. Recommendations 1The need for assisted vaginal birth can be reduced by: dedicated and continuous support during labour (I-A), oxytocin augmentation of inadequate labour (I-A), delayed pushing in women with an epidural (I-A), increased time pushing in nulliparous women with an epidural (I-B), as well as optimization of fetal head position through manual rotation (I-A). 2Encouraging safe and effective assisted vaginal birth by experienced and skilled care providers may be a useful strategy to reduce the rate of primary Caesarean delivery (II-2B). 3Safe and effective assisted vaginal birth requires expertise in the chosen method, comprehensive assessment of the clinical situation alongside clear communication with the patient, support people, and health care personnel (III-B). 4Practitioners performing assisted vaginal birth should have the knowledge, skills, and experience necessary to assess the clinical situation, use the selected instrument, and manage complications that may arise from assisted vaginal birth (II-2B). 5Obstetrical trainees should receive comprehensive training in assisted vaginal birth and be deemed competent prior to independent practice (III-B). 6When assisted vaginal birth is deemed to have a higher risk of not being successful, it should be considered a trial of assisted vaginal birth and be conducted in a location where immediate recourse to Caesarean delivery is available (III-B). 7The physician should determine the instrument most suitable to the clinical circumstances and their level of skill. Vacuum and forceps are associated with different short- and long-term benefits and risks. Unsuccessful delivery is more likely with vacuum than forceps (I-A). 8Planned sequential use of instruments is not recommended as it may be associated with an increased risk of perinatal trauma. If an attempted vacuum is unsuccessful, the physician should consider the risks of proceeding to an attempted forceps delivery versus Caesarean section (II-2B). 9Restrictive use of mediolateral episiotomy is supported in assisted vaginal birth (II-2B). 10A debrief should be done with the patient and support people immediately following an attempted or successful assisted vaginal birth. If this is not possible, ideally this should be done prior to hospital discharge and include the indication for assisted vaginal birth, management of any complications, and the prognosis for future deliveries (III-B). 11In a subsequent pregnancy, patients should be encouraged to consider spontaneous vaginal birth. However, care planning should be individualized and patient preference respected (II-3B).

Objective To provide guidelines for operative vaginal birth in the management of the second stage of labour. Options Non-operative techniques, episiotomy, and Caesarean section are compared to operative vaginal birth. Outcome Reduced fetal and maternal morbidity and mortality. Evidence MEDLINE and Cochrane databases were searched using the key words ‘‘vacuum" and "birth" as well as "forceps" and "birth" for literature published in English from january 1970 to June 2004. The level of evidence and quality of rec-ommendations made are described using the Evaluation of Evidence from the Canadian Task Force on the Periodic Health Examination. Recommendations 1.Non-operative interventions such as one-to-one support, par- togram use, oxytocin use, and delayed pushing in women using epidurals will decrease need for operative birth (I-A). 2.Manual rotation may be used alone or in conjunction with instrumental birth with little or no increased risk to the preg-nant woman or to the fetus (Ill-B). 3.Routine episiotomy is not necessary for an assisted vaginal birth (Il-lE). 4.When operative intervention in the second stage of labour is required, the options, risks, and benefits of vacuum, forceps, and Caesarean section must be considered. The choice of intervention needs to be individualized, as one is not clearly safer or more effective than the other (II-B). 5.Failure of the chosen method, vacuum and/or forceps, to achieve delivery of the fetus in a reasonable time should be considered an indication for abandonment of the method (Ill-C). 6.Adequate clinical experience and appropriate training of the operator are essential to the safe performance of operative deliveries. Hospital credentialing boards should grant privileges for performing these techniques only to an appropriately trained individual who demonstrates adequate skills (Ill-C). Validation The Clinical Practice Obstetrics Committee and Executive and Council of the Society of Obstetricians and Gynaecologists of Canada approved these guidelines.

Resume Objectif Offrir une directive clinique sur l'accouchement vaginal operatoire dans le cadre de Ia prise en charge du deuxieme stade du travail. Options Les techniques non operatoires, l'episiotomie et la cesarienne sont comparees a l'accouchement vaginal operatoire. Issue Reduction de la morbidite et de la mortalite fœtales et maternelles. Resultats Des recherches ont ete menees dans les bases de donnees MEDLINE et Cochrane afin d'y trouver les articles de langue anglaise, publies entre janvier 1970 et juin 2004, comprenant les mots cles suivants : vacuum et birth, ainsi que forceps et birth. Le niveau des resultats et la qualite des recommandations ont ete determines a l'aide des criteres d'evaluation decrits par le Groupe de travail canadien sur l'examen de sante periodique. Recommandations 1.Les interventions non operatoires (telles que le soutien individuel, l'utilisation d'un partogramme, le recours a l'oxytocine et le fait de retarder la poussee chez les femmes beneficiant d'une peridurale) limitent la necessite d'avoir recours a unaccouchement operatoire (I-A). 2.Utilisee seule ou conjointement avec un accouchement instrumental, la rotation manuelle n'entraine aucune augmentation des risques en ce qui concerne la femme enceinte ou le fœtus (III-B). 3.Le recours systematique a l'episiotomie n'est pas necessaire dans le cadre d'un accouchement vaginal assiste (II-IE). 4.Lorsqu'une intervention operatoire au cours du deuxieme stade du travail s'avere necessaire, les options, les risques et les avantages propres a la ventouse obstetricale, aux forceps. et a la cesarienne doivent etre pris en consideration. Le choix de l'intervention doit etre individualise, puisque aucune de ces methodes ne se demarquent clairement des autres en matiere d'innocuite ou d'efficacite (II-B). 5.L'echec de la methode choisie (qu'il s'agisse de la ventouse obstetricale et/ou de forceps), en ce qui a trait a l'accouchement du fœtus dans un delai raisonnable, doit etre considere comme une indication pour l'abandon de la methode en question (III-C). 6.Une experience clinique adequate et la formation appropriee de l'operateur sont essentielles a l'execution en toute surete d'un accouchement operatoire. Les comites d'agrement hospitaliers ne devraient permettre l'execution de ces techniques qu'aux personnes ayant beneficie d'une formation appropriee et ayant fait preuve d'aptitudes adequates (III-C). Validation Cette directive clinique a ete approuvee par le comite Pratique clinique – obstetrique, le comite executif et la Conseil de la Societe des obstetriciens et gynecologues du Canada.

Objective To review the benefits of and requirements for a complete second trimester ultrasound and the documentation needed. Outcomes A complete second trimester ultrasound provides information about the number of fetuses, the gestational age, the location of the placenta, and fetal and maternal anatomy. Evidence In the production of this document, the American Institute of Ultrasound in Medicine's "Practice Guideline for the Performance of Obstetric Ultrasound Examinations," the American College of Obstetricians and Gynecologists' practice bulletin, "Ultrasound in Pregnancy," and the Royal College of Obstetricians and Gynaecologists' Working Party Report, "Ultrasound Screening" were reviewed. PubMed and the Cochrane Database were searched using the words "routine second trimester obstetrical ultrasound." Values The evidence was evaluated using the guidelines developed by the Canadian Task Force on Preventive Health Care. Benefits, Harms, and Costs A routine complete second trimester ultrasound between 18 and 22 weeks and a complete ultrasound report will provide the best opportunity to diagnose fetal anomalies and to assist in the management of prenatal care. It will also reduce the number of ultrasound examinations done during the second trimester for completion of fetal anatomy survey. The costs are those involved with the performance of obstetrical ultrasound. Validation This is a revision of previous guidelines; information from other consensus reviews from medical publications has been used. Sponsors The Society of Obstetricians and Gynaecologists of Canada. Recommendations 1.Pregnant women should be offered a routine second trimester ultrasound between 18 and 22 weeks' gestation (II-2B). 2.Second trimester ultrasound should screen for the number of fetuses, the gestational age, and the location of the placenta (II-1A). 3.Second trimester ultrasound should screen for fetal anomalies (II-2B).

Resume Objectif Analyser les avantages d'un examen echographique exhaustif au cours du deuxieme trimestre et les conditions necessaires a sa tenue, ainsi que la documentation requise. Issues Un examen echographique exhaustif au cours du deuxieme trimestre offre des renseignements au sujet du nombre de fœtus, de l'âge gestationnel, de l'emplacement du placenta et de l'anatomie fœtale et maternelle. Resultats Dans le cadre de la redaction du present document, le document « Practice Guideline for the Performance of Obstetric Ultrasound Examinations » du American Institute of Ultrasound in Medicine, le bulletin de pratique « Ultrasound in Pregnancy » du American College of Obstetricians and Gynaecologists et le rapport de groupe de travail « Ultrasound Screening » du Royal College of Obstetricians and Gynaecologists ont ete analyses. Des recherches ont ete menees dans PubMed et Cochrane Database au moyen des mots « routine second trimester obstetrical ultrasound ». Valeurs Les resultats ont ete evalues au moyen des lignes directrices elaborees par le Groupe d'etude canadien sur les soins de sante preventifs. Avantages, desavantages et couts La tenue systematique d'un examen echographique exhaustif au cours du deuxieme trimestre (entre la 18 e et la 22 e semaine de gestation) et la redaction d'un rapport d'echographie exhaustif offrent la meilleure occasion de diagnostiquer les anomalies fœtales et de contribuer a la gestion des soins prenatals. Ils permettent egalement de diminuer le nombre d'examens echographiques menes au cours du deuxieme trimestre aux fins de l'exploration de l'anatomie fœtale. Les couts sont ceux qui sont mis en jeu dans le cadre de l'execution d'une echographie obstetricale. Validation Il s'agit de la revision d'une directive clinique deja publiee; des donnees issues d'autres analyses de consensus tirees de publications medicales ont ete utilisees. Commanditaire La Societe des obstetriciens et gynecologues du Canada Recommandations 1.Les femmes enceintes devraient systematiquement se voir offrir une echographie du deuxieme trimestre entre la 18 e et la 22 e semaine de gestation (II-2B). 2.L'echographie du deuxieme trimestre devrait chercher a determiner le nombre de fœtus, l'âge gestationnel et l'emplacement du placenta (II-1A). 3.L'echographie du deuxieme trimestre devrait chercher a depister les anomalies fœtales (II-2B).

Statistically, patients with severe pregnancy complications are at risk of recurrent complications, but it is less understood if patients present with similar or different placental pathologies in subsequent pregnancies. In this case report, we describe 2 consecutive adverse pregnancies in the same woman 4 years apart. The first pregnancy was diagnosed as early-onset preeclampsia and hemolysis, elevated liver enzymes, and low platelets (HELLP) syndrome, with placental maternal vascular malperfusion features, such as syncytial knots and accelerated villous maturity. In contrast, the second pregnancy was associated with normotensive fetal growth restriction and placental “immunological” lesions, such as massive perivillous fibrin deposition and chronic intervillositis. However, based on the expression of FLT1, LIMCH1, and TAP1 by quantitative polymerase chain reaction, the placentas from both pregnancies were found to exhibit an “immunological” transcriptional signature. This suggests that this small panel of gene expression markers may be able to predict the future reoccurrence of an immunological placental pathology despite no histological evidence within the first pregnancy. These results call for more studies looking at paired pregnancies of individuals with recurrent obstetric complications and confirm the importance of assessing matched transcriptional and histopathological placental information.

Fournir des directives factuelles qui favorisent l'accouchement vaginal assisté sécuritaire et efficace. RéSULTATS: Conditions préalables, indications, contre-indications, ainsi que les morbidités maternelles et néonatales liées à l'accouchement vaginal assisté. DONNéES PROBANTES: Des recherches ont été effectuées dans la base de données Medline pour trouver des articles publiés entre le 1La présente directive a été approuvée par le comité de pratique clinique - obstétrique et le conseil d'administration de la Société des obstétriciens et gynécologues du Canada. RECOMMANDATIONS.

Resume Objectifs 1.Identifier les caracteristiques echographiques indiquant un possible echec precoce de grossesse. 2.Identifier les caracteristiques echographiques d'une grossesse ectopique. 3.Proposer un algorithme diagnostique qui renforcera la securite clinique des decisions de prise en charge. Resultats 1.Exactitude et securite accrue du diagnostic d'echec precoce de grossesse 2.Exactitude et securite accrue du diagnostic de grossesse ectopique Sources de donnees Nous avons effectue des recherches dans MEDLINE et un examen de la bibliographie des articles recenses. Valeurs Le Comite d'imagerie diagnostique de la Societe des obstetriciens et gynecologues du Canada a passe en revue les donnees probantes recueillies. Les recommandations reposent sur les lignes directrices elaborees par le Groupe d'etude canadien sur les soins de sante preventifs (tableau 1). Avantages, desavantages et couts Les femmes qui presentent des saignements durant le premier trimestre peuvent recevoir un diagnostic incorrect d'avortement manque. En outre, on risque de ne pas detecter une grossesse ectopique ou de les rassurer a tort sur la viabilite de l'embryon. L'amelioration de la detection des reperes echographiques du developpement embryonnaire normal et de la connaissance des facteurs de risque lies a l'echec de grossesse sur le plan echographique pourrait donner lieu a l'elaboration de strategies de prise en charge mieux adaptees a chaque cas. Le diagnostic d'une grossesse ectopique suspectee repose souvent sur l'evaluation de marqueurs hormonaux et de caracteristiques echographiques. Par ailleurs, le diagnostic precoce de grossesse ectopique peut reduire la morbidite et la mortalite maternelles. Recommandations 1.Il est possible de poser un diagnostic de mort embryonnaire lorsque les images de l'echographie confirment les caracteristiques suivantes : sac gestationnel intra-uterin, longueur cranio-caudale embryonnaire (LCC) ≥ 7 mm, absence d'activite cardiaque. (II-2A) 2.Il est possible d'etablir un diagnostic de grossesse anembryonnaire lorsque les images de l'echographie confirment les caracteristiques suivantes : absence d'embryon et diametre moyen du sac gestationnel ≥ 25 mm. (II-2A) 3.Chez la patiente asymptomatique ou cliniquement stable, et lorsqu'on soupconne un echec precoce de grossesse, il est recommande de realiser une echographie de suivi apres une periode additionnelle de 7 a 10 jours. (III-A) 4.L'impossibilite de detecter la presence d'un sac gestationnel intra-uterin par echographie transvaginale lorsque la concentration de β-hCG depasse un niveau discriminant de 2000 a 3000 mUI/ml indique un risque eleve de grossesse ectopique. La probabilite d'une grossesse ectopique tubaire est elevee en la presence d'une masse annexielle complexe, d'un anneau tubaire ou de liquide pelvien complexe. La detection d'un embryon extra-uterin vivant donne egalement lieu a un diagnostic de grossesse ectopique. (II-2A) 5.Dans le cas d'une grossesse viable, la concentration de β-hCG augmente d'au moins 55 % en 48 heures. Une deviation par rapport a cette norme avant 7 semaines indique une grossesse ectopique ou intra-uterine non viable. (II-2A)

Objective: 1.To identify sonographic features suggestive of early pregnancy loss, 2.To identify sonographic features of ectopic pregnancy, and 3.To provide a diagnostic algorithm leading to improve clinical safety of management decision. Outcomes: 1.Accuracy and improved safety in the diagnosis of early pregnancy loss, and 2.Accuracy and improved safety in the diagnosis of ectopic pregnancy. Evidence A MEDLINE search and review of bibliographies identified articles was conducted. Values The evidence collected was reviewed by the Diagnostic Imaging Committee of the Society of Obstetricians and Gynaecologists of Canada. The recommendations were made according to the guidelines developed by The Canadian Task Force on Preventive Health Care (Table 1). Benefits, Harms, and Costs Women presenting with first trimester bleeding may be incorrectly diagnosed with a missed abortion, may have an ectopic pregnancy overlooked, or may be inappropriately reassured about viability. Improvement in the identification of the sonographic landmarks of normal embryonic development and awareness of the sonographic risk factors of pregnancy failure may lead to more case-specific management strategies. Diagnosis of suspected ectopic pregnancy often involves an assessment of both hormonal markers and sonographic features. Maternal morbidity and mortality can be reduced with an early diagnosis of ectopic pregnancy. Recommendations 1.Embryonic demise can be diagnosed when ultrasound imaging documents the following features: intrauterine gestational sac, embryonic crown-rump length ≥ 7 mm, no cardiac activity. (II-2A) 2.Anembryonic pregnancy can be diagnosed when ultrasound imaging documents the following features: no embryo and mean sac diameter ≥ 25 mm. (II-2A) 3.In clinically stable or asymptomatic patients, when a suspicion of early pregnancy loss is being considered, a follow-up ultrasound scan should be booked after an additional 7–10 days. (III-A) 4.Failure to detect an intrauterine gestational sac, by transvaginal ultrasound, when the β-hCG value exceeds a discriminatory level of 2000–3000 mIU/mL indicates an increased risk for ectopic pregnancy. With a complex adnexal mass, a tubal ring, or complex fluid in the pelvis the probability of tubal ectopic pregnancy is high, while a live extrauterine embryo is diagnostic of an ectopic pregnancy. (II-2A) 5.β-hCG values in a viable pregnancy rise at least 55% over 48 hours. Deviation from this before 7 weeks is indicative of a nonviable pregnancy, intrauterine or ectopic. (II-2A)

These joint guidelines of the Canadian Association of Radiologists (CAR) and the Society of Obstetricians and Gynaecologists of Canada (SOGC) are not rules, but an attempt to define principles of guiding practices that should generally produce optimal radiological care. The physician may deviate from existing guidelines as determined by the individual patient and available resources. Adherence to these CAR/SOGC practice guidelines will not assure a successful outcome in every situation. The practice guidelines should not be deemed inclusive of all proper methods of care or exclusive of other methods of care reasonably directed to obtaining the same results. The practice guidelines are not intended to establish a legal standard of care or conduct, and deviation from practice guidelines does not, in and of itself, indicate or imply that such medical practice is below an acceptable level of care. The ultimate judgment regarding the propriety of any specific procedure or course of conduct must be made by the physician and medical physicist in light of all circumstances

Objective To review the biological effects and safety of magnetic resonance imaging (MRI) in the obstetric patient and to review procedural issues, indications, and contraindications for obstetrical MRI. Outcomes This guideline is intended to reassure patients and clinicians of the safety of MRI in pregnancy and to provide a framework for its use. Evidence Published literature was retrieved through searches of PubMed or Medline in 2013 using controlled vocabulary and key words (e.g., MRI, safety, pregnancy). Results were restricted to systematic reviews, randomized control trials/controlled clinical trials, and observational studies published in English and in French. There were no date restrictions. Searches were updated on a regular basis and incorporated in the guideline to July 2013. Grey (unpublished) literature was identified through searching the websites of health technology assessment and health technology-related agencies, clinical practice guideline collections, clinical trial registries, and national and international medical specialty societies. Values The quality of evidence in this document was rated using the criteria described in the Report of the Canadian Task Force on Preventive Health Care (Table). Benefits, harms, and costs This article is intended to reassure obstetric care providers that if used in an appropriate manner without the use of contrast agents, MRI in the obstetrical patient is safe for mother and fetus in the second and third trimesters. Because obstetrical MRI is expensive and has limited availability in Canada, this clinical guideline is intended to encourage the judicious use of this resource.

Objective To assist clinicians in assigning gestational age based on ultrasound biometry. Outcomes To determine whether ultrasound dating provides more accurate gestational age assessment than menstrual dating with or without the use of ultrasound. To provide maternity health care providers and researchers with evidence-based guidelines for the assignment of gestational age. To determine which ultrasound biometric parameters are superior when gestational age is uncertain. To determine whether ultrasound gestational age assessment is cost effective. Evidence Published literature was retrieved through searches of PubMed or MEDLINE and The Cochrane Library in 2013 using appropriate controlled vocabulary and key words (gestational age, ultrasound biometry, ultrasound dating). Results were restricted to systematic reviews, randomized control trials/controlled clinical trials, and observational studies written in English. There were no date restrictions. Searches were updated on a regular basis and incorporated in the guideline to July 31, 2013. Grey (unpublished) literature was identified through searching the websites of health technology assessment and health technology-related agencies, clinical practice guideline collections, clinical trial registries, and national and international medical specialty societies. Values The quality of evidence in this document was rated using the criteria described in the Report of the Canadian Task Force on Preventive Health Care (Table 1). Benefits, harms, and costs Accurate assignment of gestational age may reduce post-dates labour induction and may improve obstetric care through allowing the optimal timing of necessary interventions and the avoidance of unnecessary ones. More accurate dating allows for optimal performance of prenatal screening tests for aneuploidy. A national algorithm for the assignment of gestational age may reduce practice variations across Canada for clinicians and researchers. Potential harms include the possible reassignment of dates when significant fetal pathology (such as fetal growth restriction or macrosomia) result in a discrepancy between ultrasound biometric and clinical gestational age. Such reassignment may lead to the omission of appropriate—or the performance of inappropriate—fetal interventions.

Objectives To review (1) the use of ultrasonographic-derived cervical length measurement in predicting preterm birth and (2) interventions associated with a short cervical length. Outcomes Reduction in rates of prematurity and/or better identification of those at risk, as well as possible prevention of unnecessary interventions. Evidence Published literature was retrieved through searches of PubMed and The Cochrane Library up to December 2009, using appropriate controlled vocabulary and key words (preterm labour, ultrasound, cervix, incompetent cervix, transvaginal, transperineal, cervical length, fibronectin). Results were restricted to general and systematic reviews, randomized controlled trials/controlled clinical trials, and observational studies. There were no date or language restrictions. Grey (unpublished) literature was identified through searching the websites of health technology assessment and health technology assessment-related agencies, clinical practice guideline collections, clinical trial registries, and national and international medical specialty societies. Values The evidence and this guideline were reviewed by the Diagnostic Imaging Committee and the Maternal Fetal Medicine Committee of the Society of Obstetricians and Gynaecologists of Canada, and the recommendations were made according to the guidelines developed by The Canadian Task Force on Preventive Health Care (Table 1). Benefits, harms, and costs Preterm birth is a leading cause of perinatal morbidity and mortality. Use of the ultrasonographic technique reviewed in this guideline may help identify women at risk of preterm birth and, in some circumstances, lead to interventions that may reduce the rate of preterm birth. Sponsors The Society of Obstetricians and Gynaecologists of Canada.

Resume Objectifs Analyser (1) l'utilisation de la mesure echographique de la longueur cervicale pour predire l'accouchement preterme et (2) les interventions associees a une courte longueur cervicale Issues Reduction des taux de prematurite et/ou meilleure identification des personnes exposees a des risques, ainsi que la prevention possible des interventions inutiles Resultats La litterature publiee a ete recuperee par l'intermediaire de recherches menees dans PubMed et The Cochrane Library, jusqu'en decembre 2009, au moyen d'un vocabulaire controle et de mots cles adequats (« preterm labour », « ultrasound », « cervix », « incompetent cervix », « transvaginal », « transperineal », « cervical length », « fibronectin »). Les resultats ont ete restreints aux analyses systematiques, aux essais comparatifs randomises / essais cliniques comparatifs et aux etudes observationnelles. Aucune restriction n'a ete imposee en matiere de date ou de langue. La litterature grise (non publiee) a ete identifiee par l'intermediaire de recherches menees dans les sites Web d'organismes s'interessant a l'evaluation des technologies dans le domaine de la sante et d'organismes connexes, dans des collections de directives cliniques, dans des registres d'essais cliniques et aupres de societes de specialite medicale nationales et internationales Valeurs Les resultats et la presente directive clinique ont ete analyses par le comite d'imagerie diagnostique et le comite de medecine fœto-maternelle de la Societe des obstetriciens et gynecologues du Canada, et les recommandations ont ete formulees en fonction des lignes directrices elaborees par le Groupe d'etude canadien sur les soins de sante preventifs (Tableau 1) Avantages, desavantages et couts L'accouchement preterme est l'une des principales causes de morbidite et de mortalite perinatales Le recours a la technique echographique analysee dans le cadre de la presente directive clinique pourrait contribuer a l'identification des femmes exposees a des risques d'accouchement preterme et, dans certains cas, mener a des interventions qui pourraient reduire le taux d'accouchement preterme Commanditaire La Societe des obstetriciens et gynecologues du Canada

Resume Objectif Resumer les donnees disponibles en ce qui a trait a la planification du renvoi a domicile des meres et des nouveau-nes. Issue Evaluation du lien entre la duree de l'hospitalisation et la morbidite et la mortalite maternelles et neonatales. Resultats Des recherches ont ete menees dans la base de donnees Medline, au moyen des mots cles early postpartum discharge , afin d'en tirer les articles publies entre janvier 1995 et decembre 2004 a ce sujet. Recommandations 1.Le renvoi precoce a domicile a la suite de l'accouchement entraine une hausse du risque de mortalite et de morbidite neonatales. Les programmes de suivi devraient tenir compte de cette situation. (II-2B) 2.Le bien-etre physique, psychologique et social de la mere et du nouveau-ne doit etre evalue au moment de la planification du renvoi a domicile. Les jeunes femmes primipares et monoparentales sont celles qui sont le plus susceptibles de retourner en salle d'urgence en compagnie de leur nouveau-ne. (II-2A) 3.Les programmes existants de soins post-partum au sein de la communaute sont bien utilises et apprecies. L'ajout de programmes communautaires pourrait entrainer une baisse de la mortalite, de la morbidite et des rehospitalisations neonatales. (II-2) Validation La presente declaration de principe a ete approuvee par le comite de pratique clinique-Obstetrique et par le comite executif de la Societe des obstetriciens et gynecologues du Canada.

Objective To design Canadian guidelines advising obstetric care providers of the maternal, fetal, and neonatal implications of aerobic and strength-conditioning exercises in pregnancy. Outcomes Knowledge of the impact of exercise on maternal, fetal, and neonatal morbidity, and of the maternal measures of fitness. Evidence MEDLINE search from 1966 to 2002 for English-language articles related to studies of maternal aerobic and strength conditioning in a previously sedentary population, maternal aerobic and strength conditioning in a previously active population, impact of aerobic and strength conditioning on early and late pregnancy outcomes, and impact of aerobic and strength conditioning on neonatal outcomes, as well as for review articles and meta-analyses related to exercise in pregnancy. Values The evidence collected was reviewed by the Society of Obstetricians and Gynaecologists of Canada (SOGC Clinical Practice Obstetrics Committee) with representation from the Canadian Society for Exercise Physiology, and quantified using the evaluation of evidence guidelines developed by the Canadian Task Force on the Periodic Health Exam. Recommendations 1. All women without contraindications should be encouraged to participate in aerobic and strength-conditioning exercises as part of a healthy lifestyle during their pregnancy. (II-1,2B) 2. Reasonable goals of aerobic conditioning in pregnancy should be to maintain a good fitness level throughout pregnancy without trying to reach peak fitness or train for an athletic competition. (II-1,2C) 3. Women should choose activities that will minimize the risk of loss of balance and fetal trauma. (III-C) 4. Women should be advised that adverse pregnancy or neonatal outcomes are not increased for exercising women. (II-1,2B) 5. Initiation of pelvic floor exercises in the immediate postpartum period may reduce the risk of future urinary incontinence. (II-1C) 6. Women should be advised that moderate exercise during lactation does not affect the quantity or composition of breast milk or impact infant growth. (I-A) VALIDATION: This guideline has been approved by the SOGC Clinical Practice Obstetrics Committee, the Executive and Council of SOGC, and the Board of Directors of the Canadian Society for Exercise Physiology. Sponsors This guideline has been jointly sponsored by the Society of Obstetricians and Gynaecologists of Canada and the Canadian Society for Exercise Physiology.

Objective To summarize the evidence available with regard to discharge planning for mothers and newborns. Outcome Assessment of maternal and neonatal morbidity and mortality as it relates to length of hospital stay. Evidence A Medline database search of articles from January 1995 to December 2004, using the key words early postpartum discharge. Recommandations 1.Early discharge from hospital postnatally increases the risk of neonatal mortality and morbidity. Follow-up programs should take account of this. (II-2B) 2.The physical, psychological, and social wellbeing of the mother and newborn must be assessed when discharge planning takes place. Primiparous, young, single women are most likely to return to emergency departments with their neonates. (II-2A) 3.Programs in place for postpartum care in the community are well used and appreciated. Additional programs in the community may decrease neonatal mortality, morbidity, and readmissions. (II-2) Validation This policy statement was approved by the Clinical Practice Obstetrics Committee and the Executive Committee of the Society of Obstetricians and Gynaecologists of Canada.

To review the benefits of and requirements for a complete second trimester ultrasound and the documentation needed.A complete second trimester ultrasound provides information about the number of fetuses, the gestational age, the location of the placenta, and fetal and maternal anatomy.In the production of this document, the American Institute of Ultrasound in Medicine's "Practice Guideline for the Performance of Obstetric Ultrasound Examinations," the American College of Obstetricians and Gynecologists' practice bulletin, "Ultrasound in Pregnancy," and the Royal College of Obstetricians and Gynaecologists' Working Party Report, "Ultrasound Screening" were reviewed. PubMed and the Cochrane Database were searched using the words "routine second trimester obstetrical ultrasound."The evidence was evaluated using the guidelines developed by the Canadian Task Force on Preventive Health Care.A routine complete second trimester ultrasound between 18 and 22 weeks and a complete ultrasound report will provide the best opportunity to diagnose fetal anomalies and to assist in the management of prenatal care. It will also reduce the number of ultrasound examinations done during the second trimester for completion of fetal anatomy survey. The costs are those involved with the performance of obstetrical ultrasound.This is a revision of previous guidelines; information from other consensus reviews from medical publications has been used.The Society of Obstetricians and Gynaecologists of Canada.1. Pregnant women should be offered a routine second trimester ultrasound between 18 and 22 weeks' gestation. (II-2B) 2. Second trimester ultrasound should screen for the number of fetuses, the gestational age, and the location of the placenta. (II-1A) 3. Second trimester ultrasound should screen for fetal anomalies. (II-2B).

OBJECTIVE To provide guidelines for operative vaginal birth in the management of the second stage of labour. OPTIONS Non-operative techniques, episiotomy, and Caesarean section are compared to operative vaginal birth. outcome: Reduced fetal and maternal morbidity and mortality. EVIDENCE MEDLINE and Cochrane databases were searched using the key words 'vacuum' and 'birth' as well as 'forceps' and 'birth' for literature published in English from January 1970 to June 2004. The level of evidence and quality of recommendations made are described using the Evaluation of Evidence from the Canadian Task Force on the Periodic Health Examination. RECOMMENDATIONS 1. Non-operative interventions such as one-to-one support, partogram use, oxytocin use, and delayed pushing in women using epidurals will decrease need for operative birth. (I-A) 2. Manual rotation may be used alone or in conjunction with instrumental birth with little or no increased risk to the pregnant woman or to the fetus. (III-B) 3. Routine episiotomy is not necessary for an assisted vaginal birth. (II-1E) 4. When operative intervention in the second stage of labour is required, the options, risks, and benefits of vacuum, forceps, and Caesarean section must be considered. The choice of intervention needs to be individualized, as one is not clearly safer or more effective than the other. (II-B) 5. Failure of the chosen method, vacuum and/or forceps, to achieve delivery of the fetus in a reasonable time should be considered an indication for abandonment of the method. (III-C) 6. Adequate clinical experience and appropriate training of the operator are essential to the safe performance of operative deliveries. Hospital credentialing boards should grant privileges for performing these techniques only to an appropriately trained individual who demonstrates adequate skills. (III-C). VALIDATION The Clinical Practice Obstetrics Committee and Executive and Council of the Society of Obstetricians and Gynaecologists of Canada approved these guidelines.

Objective To review the literature with respect to the use of diagnostic ultrasound in the management of twin pregnancies. To make recommendations for the best use of ultrasound in twin pregnancies Outcomes Reduction in perinatal mortality and morbidity and short- and long-term neonatal morbidity in twin pregnancies. Optimization of ultrasound use in twin pregnancies. Evidence Published literature was retrieved through searches of PubMed and the Cochrane Library in 2008 and 2009 using appropriate controlled vocabulary (e. g., twin, ultrasound, cervix, prematurity) and key words (e. g., acardiac, twin, reversed arterial perfusion, twin-to-twin transfusion syndrome, amniotic fluid). Results were restricted to systematic reviews, randomized control trials/controlled clinical trials, and observational studies. There were no date restrictions. Studies were restricted to those with available English or French abstracts or text. Searches were updated on a regular basis and incorporated into the guideline to September 2009. Grey (unpublished) literature was identified through searching the websites of health technology assessment and health technology assessment-related agencies, clinical practice guideline collections, clinical trial registries, and national and international medical specialty societies. Values The evidence collected was reviewed by the Diagnostic Imaging Committee of the Society of Obstetricians and Gynaecologists of Canada, with input from members of the Maternal Fetal Medicine Committee and the Genetics Committee of the SOGC. The recommendations were made according to the guidelines developed by The Canadian Task Force on Preventive Health Care (Table 1). Benefits, harms, and costs The benefit expected from this guideline is facilitation and optimization of the use of ultrasound in twin pregnancy.