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Introduction Labor dystocia is the most common cause of cesarean birth in the United States, yet how dystocia develops during labor remains elusive. Uterine activity monitoring has significant potential for advancing our understanding of labor dystocia. While evaluating contraction frequency and amplitude is a common component of labor dystocia management, the literature describing the relationship between measures of uterine activity and labor dystocia is heterogeneous and has not been synthesized to identify the best methods for use in clinical investigation. Methods We conducted a literature search for original research exploring the relationship between uterine activity and labor dystocia published between 2000 and 2019. Included articles were critically reviewed and synthesized. Results Across 11 identified studies, investigators employed 3 different techniques for monitoring uterine activity and 9 different measures were employed. Uterine activity measures, including Montevideo units, uterine electromyography power density spectrum and sample entropy, and the fall-to-rise ratio of contraction shape, detected patterns associated with labor dystocia or cesarean birth. Discussion The use of multiple regression with clinical covariates and a uterine activity measure increased the accuracy of predicting cesarean delivery. Uterine electromyography may be especially useful to evaluate labor dystocia phenotypes to differentiate uterine muscle fatigue from understimulation and lead to algorithms for increased precision in the diagnosis of labor dystocia and innovative approaches to treatment.

In this issue, Hautakangas et al report that "we found significantly lower intrauterine pressure (IUP) in failed Trial Of Labour After Caesarean (TOLAC), compared with Vaginal Birth After Caesarean", although "the dosages of oxytocin tended to be higher among failed TOLACs". They commented that "it seems that raising the oxytocin dosage does not necessarily improve uterine contractile activity in this group". Why is this?

Objective To describe the outcomes of patients transferred to King Edward Memorial Hospital (KEMH) with signs of labour at preterm gestations. Design A retrospective observational study of the 69 cases transferred to KEMH during 2015. Setting Patient transfers from all locations across Western Australia (WA) to the sole tertiary perinatal centre in Perth. Participants Pregnant women within WA with threatened or actual preterm labour (PTL) or preterm prelabour rupture of membranes (PPROM) between 23 and 32 weeks gestation. Main outcome measures The occurrence of delivery during the admission and time-to-delivery as well as length of admission and association between clinical factors and time-to-delivery. Results The percentage of the study population delivered during the admission following transfer was 72.5%. Eighty-six per cent of those who delivered did so within 72 hours of transfer. The median time from transfer to delivery was 1 day. Sixty-three per cent of those who did not deliver during the admission progressed to 36 weeks gestation. Patients transferred with PPROM were less likely to deliver during the admission compared to those with uterine activity (50% versus 19.6%, P = 0.007) and nulliparas were more likely to deliver (93.5% versus 55.3%, P Conclusion The majority of women transferred with signs of PTL progress to delivery during the same admission with the highest risk of delivery being the first 72 hours following transfer. If the pregnancy is ongoing at 72 hours, there is a reasonable chance of progression to late preterm gestation supporting the return of woman to their place of origin for antenatal care following discharge.

New Findings What is the topic of this review? How do medicinal plants act on the myometrium? What are the underlying mechanisms whereby medicinal plants exert their effects? What advances does it highlight? We show that medicinal plants can affect uterine contraction at many loci. These studies give us a better understanding of how medicinal plants work on the uterus and can be applied in other areas of smooth muscle physiology, as well as pharmacy and medicine. This knowledge is also useful for developing new agents with potential to improve women's reproductive and gynaecological heath. This report summarizes work investigating the effects of some medicinal plants on uterine contraction. As there is a clinical need to find better drugs to help control uterine activity, and novel compounds are sought, the mechanisms whereby the medicinal plants exert their effects, as well as their major compounds, are discussed. By identifying the plants, major constituents and mechanisms, this review also illustrates the potential for development of new drugs, so that better ways to treat uterine disorders will be available to women worldwide.

Objective. To analyze typical maternal heart rate (MHR) patterns in the first and second stages of labor. Design. Observational study. Setting. Tertiary care community hospital. Population. Normal term parturients with epidural anesthesia. Methods. Confirmed MHR and uterine activity were simultaneously recorded. The average MHR was analyzed 10 seconds before, as well as at the peak of, each contraction and/or pushing effort. Each woman contributed one datapoint at each time point to the analysis. Main outcome measure. Change in MHR during contractions. Results. First stage: 7.6±2.1 contractions per woman (n=18) were analyzed. Average MHR decreased during contractions: from 83±13 to 74±10bpm; p 100bpm in three women (17%) in the first stage, and in four women (27%) in the second stage. Peak MHR >140bpm occurred during pushing in 20%. Conclusion. Decreases in MHR during contractions in the first stage of labor can mimic fetal heart rate (FHR) accelerations as well as early type decelerations. Thus, first stage tracings with a low baseline and early type decelerations may be maternal in origin and FHR should be independently confirmed in such tracings. Because second stage MHR accelerations generally show greater amplitude than FHR accelerations, tracings with repetitive accelerations during contractions (especially when Δ >20bpm) should be considered MHR until proven otherwise.

Uterine activity measured by quantifying active contraction area in induced labour showed an initial significant steep increase (incremental phase) followed by a stable phase when the uterine activity was about 1750 k Pas/15 min in nulliparae and multi-parae with poor cervical score; it was 1500 k Pas/15 min in multiparae with good cervical score. Once this was achieved, further increase in oxytocin dosage did not increase uterine activity but instead revealed a tendency to hypertonic uterine contractions. A marked rise in uterine activity was observed in the late first stage of labour (terminal phase) despite no increase in oxytocin in patients with good cervical scores (>6) at induction but not in those with poor cervical scores (

A new fibreoptic pressure transducer was used to measure uterine activity in labour, and the results were compared with those obtained with the catheter-tip bridge strain gauge transducer. Readings were obtained from 8 patients in spontaneous labour, and a total of 565 contractions were analysed. When all contractions were analysed the coefficient of variation ranged from 11.24 to 42.74. In 2 patients with vast difference in pressure readings one of the catheters had slipped into the lower uterine segment, when these 2 cases were not considered the coefficient of variation ranged from 11.24 to 21.18. Even in the others there were transient periods lasting 5 to 15 minutes when the pressure difference was greater than 10 mmHg between the 2 catheters. When they were excluded from analysis, along with the 2 cases where one of the catheters was displaced, the coefficient of variation ranged from 9.30 to 16.05. The fibreoptic pressure transducer appears to be a safe, convenient and fairly accurate means of assessing uterine activity. But one must be aware that a catheter giving low readings compared with the initial period soon after insertion may be due to displacement of the transducer tip to the uterine lower segment.

Transport of women in preterm labour in Western Australia is conducted in small fixed wing aircraft over distances up to 2,000 km (1,200 miles). In recent years β-sympathomimetic inhibition of uterine activity has been employed to reduce the risk of delivery during transfer. This study reports the outcome of routine use of this therapy in which at times classical contraindications have not been observed. During 1983 and 1984, 99 consecutive maternal aerial transfers for preterm labour using β-sympathomimetic drugs by infusion resulted in only 1 case of pulmonary oedema and 2 of maternal hyperglycaemia. There were no deliveries during the flights. The results of this study suggest β-sympathomimetic inhibition of uterine activity for women in preterm labour is safe and efficacious therapy for long distance aeromedical evacuation in small aircraft.

Uterine activity was quantified using a transducer tipped intrauterine catheter in 75 nulliparous women with dysfunctional labour. The active contraction area profiles in these women were below the median levels reported for those who had normal progress of labour from our institution. When uterine activity was augmented with oxytocin, 90.7% progressed in labour and delivered vaginally. Six patients (8%) showed poor progress despite good uterine activity and had to be delivered by caesarean section (CS) for failure to progress and signs of cephalopelvic disproportion. The pre- and post-augmentation uterine activity were similar in those who delivered vaginally or by CS and was not helpful in identifying those who had cephalopelvic disproportion. Of the 75 women who had slow progress of labour, 50 had a contraction frequency of less than 1 in 3 min whilst 25 had a minimum frequency of 1 in 3 min or more. All except one in the latter group delivered vaginally when oxytocin was titrated to achieve a contraction frequency of 1 in 2 to 2 1/2 min which were clinically judged to be adequate based on a duration greater than 40 sec. Oxytocin should be titrated to achieve a target contraction frequency of 1 in 2 to 2 1/2 min lasting greater than 40 sec to achieve good obstetric outcome in those with dysfunctional labour.

Calcium entry blockers have a well documented relaxing effect of smooth muscle, vascular as well as non-vascular. Mainly as a consequence of this action, the drugs have been used for treatment of several non-cardiac disorders where hyperactivity of smooth muscle is considered to have an important role in the pathogenesis. In this short review some of these extracardiac effects of calcium entry blockers are discussed and also their clinical application.

A new isolation procedure for Kalata polypeptides from the tropical plant Oldenlandia affinis DC is described. Fractions were screened by thin-layer chromatography, and Van Urk positive fractions were tested for oxytocic activity in estrogenized rat uteri. By using this procedure, we were able to isolate and characterize three macrocyclic polypeptides with uterine activity. Their amino acid sequence and biological effects have been analyzed, and their NMR spectra were compared with those of the earlier ones. All three peptides showed hemolytic activity on human blood, and were tested for antibiotic effect against E. coli, Staphylococccus aureus, and Hemophilus influenzae.

A better understanding of the mechanisms that generate and modulate uterine contractility is needed if progress is to be made in the prevention or treatment of problems in labour. Dysfunctional labour describes the condition when uterine contractility is too poor to dilate the cervix, and it is the leading cause of emergency Caesarean sections. Recently, insight has been gained into a possible causal mechanism for dysfunctional labour. Study of the physiological mechanisms that produce excitation in the uterus, the subsequent Ca(2)(+) signals and biochemical pathway leading to contraction has underpinned this progress. In this review, I give an account of excitation-contraction signalling in the myometrium and explore the implications of recent findings concerning lipid rafts for these processes. I also discuss how changes of pH are fundamentally enmeshed in uterine activity and biochemistry and explore the effect that pH changes will have on human myometrium. Finally, I present the evidence that acidification of the myometrium is correlated with dysfunctional labour and suggest the processes by which it is occurring. It is only by gaining a better understanding of uterine physiology and pathophysiology that progress will be made and research findings translated into clinical benefit for women and their families.

To analyze the effects of uterine contractions on ductus venosus (DV) pulsatility during the first stage of labor.Twenty healthy women were examined. Measurements were taken at three stages of cervical dilatation (4 cm, 4-7 cm andor=8 cm) during and between contractions. Peak velocity during ventricular systole (S) and atrial contraction (A), pulsatility index for veins (DV PIV), ductus venosus index (DVI) and the S/A ratio were measured.The DV was observed successfully in 16 cases. The mean S velocity did not change significantly (64 cm/s during and 65 cm/s between contractions). The mean A velocity decreased significantly from 35 cm/s measured between contractions to 29 cm/s during contractions (P0.0001). The mean DV PIV and DVI were significantly higher during contractions (0.72 and 0.55) than between contractions (0.57 and 0.45) (P0.0001). There were no significant differences in means between stages of cervical dilatation.Significant differences during and between uterine contractions can be observed in DV pulsatility during normal labor.

In 1950, the World Health Organisation (WHO) defined prematurity as a birthweight of 2500 g or less and in 1961 as a gestational age of less than 37 weeks. The time in between marks an era in which there was growing recognition of the importance of gestational age at birth and how to influence it. The latter was facilitated too by the development of tocography, which permitted some semi-objective measurement of uterine contractility. Along with it, came a growing interest in agents that could control uterine contractility beyond the earlier classical approaches of hormones and gastrointestinal spasmolytics. Hence, the early 1960s saw much research interest in agents, such as nylidrine, isoxsuprine, and orciprenaline that could suppress uterine contractility as one of their many beta-agonist properties. Subsequently, two approaches would be used to shift the balance towards uterine function over and above the influence on other bodily functions. One consisted of supplementing these drugs with agents, such as calcium antagonists and beta-receptor blockers that were hoped to suppress non-uterine actions. The other was a search for drugs in the same class with greater uterospecificity and more selective binding to uterine as opposed to other receptors. Neither of these approaches has ever fully fulfilled the hopes that were pinned on them, but they resulted in the availability of a large number of agents to suppress uterine contractility. The advent of prostaglandins as regulators of uterine contractility and the ability to suppress their biosynthesis saw another range of attempts to suppress uterine activity. They included aspirin, sodium salicylate, flufenamic acid, sulindac and indomethacin, but some were clearly based on a defective understanding of how uterine prostaglandin synthesis can be influenced. In the meantime, a flurry of other agents came and went, often more than once, testifying to the ingenuity of clinicians in trying to solve a problem that is poorly understood. Some, such as relaxin and ethanol, came and disappeared. Others, such as calcium antagonists, entered the scene as protectors against the non-uterine effects of other agents, went, and re-entered the scene in their own right. Still others, such as magnesium sulphate, came, lingered around, and became credited with effects in preterm labour that do not depend on affecting uterine contractility. Amidst this all arose the term tocolysis, coined in 1964 by Mosler from the Greek stems ‘τοκοζ’ and ‘λυeιν’, to epitomise all of this ingenuity.

Summary: There is a surprising lack of information on antenatal patterns of uterine activity in the normal obstetric population, with the majority of research having focussed on women at high-risk for preterm birth. We conducted a prospective longitudinal study to investigate patterns of uterine activity in women with singleton gestations at low-risk for preterm birth. Twenty pregnant women were recruited and their uterine activity was recorded using ambulatory tocodynamometry twice weekly throughout the latter half of pregnancy. The collected data were transmitted to a central receiving station for analysis. As gestation advanced there was a progressive increase in the median number of contractions detected per hour, peaking and stabilizing at 37–40 weeks (median of 0 contractions/hour at 20–24 weeks rising to 5.4 contractions/hour at 37–40 weeks). In those women with uterine activity, contraction duration and amplitude of deflection significantly increased as gestation advanced. There was a progressive increase in the number of higher amplitude contractions throughout the third trimester. Increasing parity was not associated with increasing antenatal uterine contraction frequency. No association between normal daily physical activity and uterine contraction frequency was evident throughout gestation. In normal human pregnancy there is a steady, progressive increase in the frequency, duration and amplitude of antenatal uterine activity throughout the latter half of gestation. The uterine contractile profile alters from one of a low amplitude, low frequency pattern in the second trimester to a higher amplitude, higher frequency pattern at term.

Thirty term pregnant women with one previous cesarean section and with unripe cervices were given 0.5 mg prostaglandin E2 in gel strictly intracervically for cervical ripening and labor induction. Fifteen out of these 30 women (50%) were vaginally delivered within 24 hours. The cervical ripeningllabor induction was considered a failure in two women. In one woman, an episode of hypercontractility was registered. After tocolytic therapy the uterine activity was normalised and the woman had a normal vaginal delivery. The frequency of cesarean sections was 8/30 (27%). At the operations no insufficencies in the uterine scars were noted. Conclusively, strict intracervical application of 0.5 mg prostaglandin E2 in gel can be used for cervical ripening and labor induction also in women with one previous cesarean section.

Uterine activity during the first stage of labour was measured by an intrauterine transducer in 22 women induced with intravaginal PGE2 gel, in 37 induced by amniotomy and intravenous oxytocin, and in nine women in spontaneous labour. The nulliparous women in the PGE2 gel group had a significantly longer pre-established phase of labour and a significantly shorter established phase than nulliparae induced by amniotomy and oxytocin. The mean levels of total uterine activity (kPas) during labour and the uterine activity integrals (kPas/15 min) were significantly lower in nulliparae induced with PGE2 gel than in those induced by amniotomy and oxytocin. These findings suggest that PGE2 gel has a positive, beneficial effect on cervical compliance during the pre-established phase, resulting in less myometrial effort during established labour. These effects were less evident in parous women, probably because of an innate lower cervical resistance due to their previous labours. Uterine activity patterns during the 4 h leading to full cervical dilatation in nulliparae were similar in labours induced with PGE2 gel and spontaneous labours, whereas labours induced by amniotomy and oxytocin exhibited a significantly different pattern. Expulsion of the fetus during normal labour is a function of both uterine contractions and a decrease in the cervical resistance and the data suggest that induction by PGE2 gel more closely mimics spontaneous labour, whereas the predominant effect of oxytocin is to stimulate myometrial activity.

Study objective: To evaluate the effect of epidural and pethidine analgesia on the frequency of uterine contractions during the first stage of labor. Design: Retrospective study. Setting: Delivery ward of a public hospital. Patients: Forty consecutive parturients. Measurements and main results: The mean number of contractions in the 30 min before administration of pethidine analgesia was 8.2±1.7 as compared to 8.7±1.3 after administration of the analgesia. The mean number of contractions in the 30 min before administration of epidural analgesia was 8.0±1.4 as compared to 8.8±1.9 after administration of the analgesia. The differences between the two groups and between the number of contractions before and after the administration of both types of analgesia were not statistically significant. Conclusion: Properly and timely administered epidural analgesia during the first stage of labor has no effect on frequency of uterine activity.

Twenty-two women > 24 weeks' gestation with a central placenta praevia were monitored to determine if an increase in uterine activity precedes bleeding in patients with central praevias. Monitoring of all subjects began at 26.3 +/- 4.4 weeks and continued until 37 weeks (or delivery if preterm). All subjects had at least one haemorrhage, 7 women had 2, and 4 subjects had 3 episodes of bleeding. Only 3 patients delivered at term while the remainder (86%) delivered preterm. The gestational age at first episode of bleeding was 29.1 +/- 3.6 weeks and at delivery was 34.3 +/- 3.3 weeks. Nine women (41%) had an increase in uterine activity above baseline the day or the day preceding the first haemorrhage. The increase in uterine activity was not statistically significant when compared to the 6 days prior to bleeding when all 22 patients were considered.

It has been our anecdotal experience that midwives and doctors sometimes perceive uterine contractions to diminish in strength and frequency following the administration of epidural anesthesia. This is probably an incorrect perception, as there is no physiological reason for this phenomenon [1]. Nevertheless, this probable misconception is of some importance, as a perceived reduction in uterine activity could lead to inappropriate use of oxytocic agents. The hypothesis of this study was that the clinical assessment of uterine activity is reduced following the administration of epidural anesthesia. Primiparous women with singleton pregnancies in spontaneous labor who had epidural anesthesia, were selected for this retrospective study. They were identified within a maternity unit of 3500 deliveries/year, between June and December 2003.

Objectives: To prospectively compare the efficacy and tolerance of two techniques of amniodrainage used in the treatment of symptomatic polyhydramnios: syringe aspiration (SA) and continuous vacuum depression (VD). Patients and Methods: Prospective randomised study, performed over 37 months. The main comparison criterion was maternal pain, blindly assessed by a midwife using a visual quantitative scale (EVA from 0 to 100 points). Comparison also included: duration and volume of fluid drained, need to stop the procedure because of maternal pain, uterine activity after drainage, foetal tolerance controlled with CTG (FHR blindly analysed by 2 obstetricians) and absence of placenta abruption controlled by histological examination of the placenta. We calculated that 35 patients would be necessary in each group to show a 20 points difference on the EVA with a power of 80% (alpha: 0.05). Results: 80 amnioreductions were performed in 53 patients. The two groups were comparable for the tested variables (age, parity, term, deepest pool and amniotic fluid index before drainage, uterine contractility, tocolysis) as well as for the aetiology of polyhydramnios. Drained volume was significantly higher in the VD group (2540 ml +/− 860 versus 1250 ml +/− 530; p < 0.01) and the drainage duration significantly shorter (12 mn +/− 10 versus 38 mn +/− 25; p < 0.01). Maternal pain was significantly lower in the VD group compared to the SA group (25 +/− 12 vs. 55 +/− 22; p < 0.01). No significant difference was noted in uterine contractility or FHR abnormalities between the two groups and they were no occurrence of clinical placental abruption. In four cases, histological analysis of the placentas revealed the presence of old placental infarctions (three in the SA group and one in the VD group). Conclusion: Continuous vacuum depression appears to be faster and has a better maternal tolerance than syringe aspiration.

The present study was undertaken to investigate the role of bacterial vaginosis (BV) as a possible causative factor in prematurity, to evaluate biochemical changes in preterm labor, and to compare the efficacy of indomethacin and nylidrin in arresting preterm uterine activity.

Purpose: This study was to determine if cervical parameters, as assessed by transvaginal ultrasound, were predictive of spontaneous preterm birth in women following an episode of threatened preterm labor (TPL). Methods: Women with a singleton pregnancy (20–34 weeks gestation) and intact membranes were enrolled following admission for TPL. The transvaginal ultrasound assessment of the cervix was performed when uterine activity had ceased. Only the ultrasound relating to the episode of suspected preterm labor is reported. Results: Sixty women had a transvaginal scan performed at a gestation of 27.7 ± 3.7 weeks (mean ± SD) (range 20.1–33.7 weeks). Cervical parameters were significantly different in women who delivered preterm (shorter closed endocervical canal length –P 5 mm). Of these, 16 (64%) delivered preterm (

Cervical cerclage is the traditional management of cervical incompetence. Uterine activity among these patients has never been studied. This retrospective report details the contraction frequency in 96 patients with cerclage who underwent daily home uterine activity monitoring. Twenty-three percent (22) developed preterm labor and 12% (11) had preterm delivery related to failed tocolysis or rupture of the membranes. Uterine activity in the group who developed preterm labor was significantly greater than in those who labored at term. The objective contraction frequency data obtained by uterine activity monitoring are of clinical significance to physicians managing such patients.

Nitrous oxide analgesia was introduced into obstetrics by a young Polish-Russian physician who manufactured the gas himself, mixed it with oxygen, humidified the mixture with water vapor, and devised a mouthpiece for self-administration. After assessing the results on himself, he evaluated the effects on pain relief, maternal emotion, and maternal and fetal heart rates, as well as on the frequency, duration, and strength of uterine contractions in 25 parturients. He recognized that, in contrast to chloroform, nitrous oxide did not alter uterine activity. He concluded that the advantages of nitrous oxide administration far outweighed its disadvantages.

Home uterine activity monitoring and daily perinatal nursing contact were used in patients at risk for preterm labor in a rural area using provider consultation with a perinatologist in a tertiary center. In the management of 25 subjects at high risk for preterm delivery, it was noted that the patients had decreased anxiety. They felt that the service was beneficial to them and allowed them to stay in their local area. The providers felt confident that this daily contact allowed them to manage the patients without transfer to the tertiary center. Likewise, concerning women who developed preterm labor, the physicians were confident that the diagnosis would be early enough that transport, if necessary, could be carried out safely. Finally, the physicians felt that verbal reassurance from the perinatologist and weekly written contact with the monitoring service facilitated local management of such patients, particularly as it concerned administration of tocolytic agents.

It has been shown that an intensive system of preterm birth prevention using home uterine activity monitoring can decrease the number of early births. Such a system was employed in 130 public assistance (Medicaid) patients who were at high risk for preterm birth. A retrospective review of the pregnancy outcome in these subjects was conducted and their data exposed to a model for projected patient care cost. The incidence of preterm labor in the at-risk group was 46%, with an average prolongation of pregnancy of 4.9 weeks. The occurrence of preterm delivery for failed tocolysis or advanced cervical dilatation was less than 10%. Based on a cost-analysis model that considered newborn charges and monitoring expenses, nearly [corrected] $3 million (an average of $21,813 [corrected] per patient) was saved using this system.

Ambulatory tocodynamometry has been used for some time to record uterine activity during pregnancy. Most studies, however, have been performed in the third trimester (more than 24 weeks). The current study was initiated to assess uterine activity at earlier gestational ages. One hundred thirty-seven patients were studied between 14-19 weeks' gestation (inclusive). Seven patients who were being monitored were noted to have preterm labor, and six of these seven were found to have increased uterine activity before the diagnosis of preterm labor. There was no difficulty encountered in the vast majority of cases in recording objective, accurate uterine activity information even at these early gestational ages. There was an increase in the uterine activity (during the 18th and 19th weeks) in patients destined to develop preterm labor later in gestation as compared with the contraction pattern of those who labored at term. This study demonstrates that accurate uterine activity information can be gained at these early gestational ages and that when increased contraction frequency is present, it is related to preterm labor.

Daily antepartum nursing contact and ambulatory uterine activity monitoring have been used for the early detection of preterm labor. However, it may be difficult to separate true labor from false labor. In this study, the uterine activity records of 110 women at risk for preterm birth with excessive contraction frequencies were evaluated by blinded reviewers. Maternal symptomatology and uterine activity characteristics such as low-amplitude high-frequency contractility, contraction amplitude, contraction duration, contraction interval, and contraction rhythmicity were assessed for their ability to differentiate true from threatened preterm labor. Neither maternal symptomatology nor any uterine activity characteristic other than contraction frequency could differentiate true from threatened preterm labor. Antepartum uterine activity monitoring should continue to rely on contraction frequency to identify the woman at risk for premature labor.

Forty private patients using a home uterine activity monitoring system and daily contact with nursing staff (Term Guard monitor and Tokos Perinatal Nursing Service; Tokos Medical Corp., Santa Ana, CA) were surveyed after delivery. Twenty-seven responses (67.5%) were obtained. The majority of the responding patients (81%) felt that the monitor helped their pregnancy and 92% would recommend it to family and friends. Eighty-five percent thought that the monitor and related nursing services would be something that they would use in future pregnancies. No subject concluded that the monitor depersonalized their obstetric care. Forty-one percent of the patients felt that the device was an intrusion into their life-style. Seventy-eight percent thought that the device was beneficial in their understanding of preterm labor and in learning to perceive their own baseline uterine activity. Almost 60% of the subjects noted that the monitor was useful in determining uterine activity because they did not perceive any contractions. Approximately 65% felt that unnecessary trips to the hospital for prolonged monitoring were prevented by the availability of 24-hour-a-day, 7-day-a-week emergency transmission and nurse contact. Nearly three-fourths of the patients felt that unnecessary calls to the physician were prevented by their ability to monitor. In summary, the services were well accepted by the patients and, despite the intrusion into their life-style, most felt that home uterine activity monitoring improved the outcome of their pregnancy.

Uterine activity was measured quantitatively during subsequent labor after prostaglandin E2 gel (PGE2). Thirty primigravidae with a low Bishop score were included in this randomized double-blind study. Fewer women who received PGE2 required subsequent surgical induction. The pattern of uterine activity was different. Cervical dilatation was achieved with less uterine activity in the PGE2 group, especially during the shorter latent phase.

The uterine activity of women during induced labour was analysed with a real-time Commodore PET 2001 series microcomputer. The active contraction area was measured in torr-min (1 torr = 0.133 kPa) per 10 min epochs [uterine activity unit (UAU)/10 min]. Surgical induction was followed immediately by administration of a geometric oxytocin infusion and all patients received epidural analgesia. Twenty-eight primigravidae for whom inductographic and partographic progress were normal had a mean 'stable phase' uterine activity of 118 +/- 2 SD 43 UAU/10 min (identical to 942 +/- 2 SD 343 kPas/10 min) whereas 15 multiparae had a mean 'stable phase' of 83 +/- 2 SD 34 UAU/10 min (identical to 662 +/- 2 SD 271 kPas/10 min). This difference was significant (P less than 0.01). The construction of uterine activity charts is described and their clinical application discussed.

The effect of nipple stirnulation on uterine activity, foetal heart rate and plasma oxytocin level in healthy full term pregnant women was studied. Ten women in weeks 38–39 of pregnancy stimulated their nipples for 30 min. Nine of the ten experienced uterine contractions. One woman showed signs uterine hyperactivity (frequent contractions) and foetal heart rate decelerations. Blood samples were drawn at 15 s intervals during 5–6 contractions and oxytocin levels were measured with radioimmunoassay. Oxytocin levels rose significantly during the nipple stimulation and short bursts of oxytocin were recorded during contractions. Nipple stimulation has been used to induce labour and our data may suggest that oxytocin released in response to such stimulation is responsible for the contractions induced.

Summary A study was made of the characteristics of oxytocin-induced labour. Twelve patients with, and eight without membrane rupture were closely matched for factors likely to influence the character and duration of labour. In both groups uterine activity increased until a stable state was achieved following which there was little alteration until delivery. The duration of labour was shorter in the group with ruptured membranes as compared with intact membranes although, paradoxically, the uterine activity tended to be greater when the membranes were intact.

The influence of epidural block with bupivacaine (Marcaine-adrenalin) on fetal heart rate, uterine activity, and the frequency and intensity of contractions was studied in twenty-five nulliparae at term. Uterine activity was found to decrease during the first 30 minutes following epidural block. In the time interval 30 to 40 minutes after epidural block uterine activity increased again and attained the same level as during the last 10 minutes before analgesia. The frequency of uterine contractions did not decrease after the block. The lower levels of uterine contractility were due only to a lower amplitude of the contractions. The regularizing effect of epidural analgesia on incoordinate uterine action was noted. The recording of fetal heart rate in the time interval studied revealed no pathological findings. Mode of delivery, mean labour duration and Apgar scores after epidural block were comparable with earlier studies of a larger patient population. This study suggest that epidural analgesia does not induce any important changes in fetal heart rate but temporarily decreases uterine activity.

To investigate the role played by chronic intrauterine insult in the genesis of neurodevelopmental disability (NDD), three analyses have been applied to a case-controlled study which compared a population of children with NDD with a control group of normally developed children. In the first analysis, average birthweight in children with NDD was 3138 g (SD 592) which was significantly less than in normally developed children, 3280 g (SD 491) (P less than 0.0005). After correction for confounding factors, birthweight-for-gestation (Z score) remained lower in children with NDD (-0.42) than normal children (-0.21) (P less than 0.0025). In the second analysis the fetal growth achievement of children, who had NDD after the prenatal complications, severe hypertension, unclassified antepartum haemorrhage and preterm uterine activity, was significantly less (Z score, -0.76) than children who were normally developed after the same maternal prenatal complications (Z score, -0.37) (P less than 0.03). In the third analysis, a risk analysis to assess the relative importance of fetal growth achievement and prenatal complications in the genesis of NDD suggested that the latter was the dominant factor. These data are consistent with the hypothesis that prenatal complications, severe enough to retard fetal growth, can compromise fetal brain development and make an important contribution to NDD.

Uterine activity was measured during the second stage of normal labour in 20 patients with and 31 patients without epidural analgesia. There was a significantly lower uterine activity integral (UAI) in patients having epidural analgesia, and it is suggested that this may contribute to the increased rate of instrumental delivery associated with epidural analgesia.

Summary: This study was designed to investigate the efficacy of simultaneous oxytocin infusion in physiological doses in patients in whom amniotomy had been performed to induce labour. One hundred patients were studied and, as far as possible, these were obstetrically homogeneous. In all patients, conditions favourable for induction were present. All of the 50 patients induced by amniotomy and simultaneous oxytocin infusion delivered within 24 hours (1 patient required a Caesarean section operation for fetal distress), whereas only 34 of the 50 induced by amniotomy alone did so. The study confirms the generally accepted view that 95% of patients will be delivered vaginally after surgical induction of labour. It also confirms Mac Vicar's study (1971) that 2% of patients induced by amniotomy will require Caesarean section for defective uterine activity alone. To shorten the induction-delivery interval, amniotomy should be performed and, immediately thereafter, an oxytocin infusion commenced. In favourable cases, the oxytocin should be given by intravenous infusion in physiological doses. This requires minimal staff supervision.

Summary. A detailed study has been made of uterine activity in a group of 21 unselected women in spontaneous labour. Measurements were made of contraction frequency, active pressure, Montevideo units and active contraction area. The level of Montevideo units were comparable with -values previously reported in spontaneous labour. Active contraction area correlated better than any of the other measures with the rate of cervical dilatation in the active phase of labour (r= 0.69). The mean contractionarea was 1099 (SD 333) kPas/15 min.

Summary Uterine activity was measured in 60 women whose first labour was progressing slowly in the active phase. The mean level of active contraction area (uterine activity integral, UAI) before oxytocin augmentation was 898 (SD 458) kPas/15 min. UAI increased significantly with time, even in women not given oxytocin. UAI increased logarithmically with increasing oxytocin infusion rate. Levels of uterine activity before and after oxytocin infusion are correlated positively such that the higher the initial level of UAI the higher the UAI in response to oxytocin. However, the regression line approaches the line of identity such that even with high doses of oxytocin UAI would not be likely to exceed 2500 kPas/15 min. There is a positive correlation between uterine activity and cervical dilatation rate in unstimulated labour; however, this is less evident following oxytocin infusion. Increases in uterine activity below 1200 kPas/15 min result from both higher frequency and active pressure, whereas above 1200 kPas/15 min any increase is due mainly to a rise in frequency.