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STUDY QUESTION Are the early pregnancy outcomes of IVF pregnancies conceived with donor sperm different to those conceived with partner sperm? SUMMARY ANSWER Pregnancies conceived with donor sperm have a lower odds of early pregnancy loss and ectopic pregnancy compared to pregnancies conceived with partner sperm. WHAT IS KNOWN ALREADY The number of cycles using donor sperm has risen significantly in recent years. Adverse early pregnancy outcomes have a negative impact on women and their partners. The evidence available to date regarding early pregnancy outcomes for pregnancies conceived with IVF donor sperm is limited by low numbers and lower-quality studies. STUDY DESIGN, SIZE, DURATION This is a retrospective cohort study of 1 376 454 cycles conceived with either donor or partner sperm between 1991 and 2016 as recorded in the Human Fertilisation and Embryology Authority (HFEA) Register. PARTICIPANTS/MATERIALS, SETTING, METHODS The HFEA has recorded data on all fertility treatments carried out in the UK from 1991 onwards, and it publishes this data in an anonymized form. This study assessed the outcomes of all pregnancies conceived with donor sperm and compared them to those conceived with partner sperm among IVF cycles recorded in the HFEA anonymized dataset from 1991 to 2016. Cycles that included intrauterine insemination, donor oocytes, preimplantation genetic testing, oocyte thaw cycles and alternative fertility treatments were excluded. The outcomes of interest were biochemical pregnancy, miscarriage, ectopic pregnancy, stillbirth and live birth. Logistic regression was used to adjust for confounding factors including age of the female partner, cause of infertility, history of previous pregnancy, fresh or frozen cycle, IVF or ICSI, number of embryos transferred, and year of treatment. Results are reported as adjusted odds ratios (aOR) and 95% CIs. MAIN RESULTS AND THE ROLE OF CHANCE This study found reductions in the odds of biochemical pregnancy (aOR 0.82, 95% CI 0.78–0.86), miscarriage (aOR 0.93, 95% CI 0.89–0.97), and ectopic pregnancy (aOR 0.77, 95% CI 0.66–0.90) among pregnancies as a result of the use of donor sperm as opposed to partner sperm. LIMITATIONS, REASONS FOR CAUTION This study is retrospective and limited by the constraints of routinely collected data. No data were available for maternal characteristics such as BMI, smoking and partner age, which could all be potential confounders. Clustering of multiple pregnancies within women could not be accounted for as the data are reported only at the cycle level with no maternal identifiers. WIDER IMPLICATIONS OF THE FINDINGS This study has demonstrated that there are no increased risks of adverse pregnancy outcome with donor sperm pregnancies. The reduction in miscarriage in pregnancies using donor sperm suggests that sperm could have a role in miscarriage, as the selection process for being accepted as donor is stringent. STUDY FUNDING/COMPETING INTEREST(S) No external funding was sought for this study. C.A. has received funding from Ferring to attend a UK meeting for trainees in reproductive Medicine. A.M. has received funding from Ferring, Cook, Merck Serono, Geodon Ritcher, and Pharmasure for speaking at, or attending, meetings relating to reproductive medicine. She has also participated in a Ferring advisory board. S.B. has received grants from Tenovus and the UK Medical Research Council. She has also been supported with a Medical Research Scotland PhD studentship. TRIAL REGISTRATION NUMBER N/A.

STUDY QUESTIONAre perinatal outcomes following fresh blastocyst versus fresh cleavage stage embryo transfer (ET) different in singletons, twins, and between singleton siblings?SUMMARY ANSWERSingleton babies conceived following fresh blastocyst, versus cleavage stage, ET are less likely to be small for gestational age (SGA) or to have a congenital anomaly (a result confirmed by comparing singleton siblings), while singletons born following fresh blastocyst ET were at a higher risk of being large for gestational age (LGA) than their sibling born following fresh cleavage stage ET.WHAT IS KNOWN ALREADYBlastocyst stage transfer is now the preferred strategy in most IVF units. Previous studies have suggested that babies conceived through blastocyst transfer are at increased risk of preterm birth and LGA.STUDY DESIGN, SIZE, DURATIONA national population-based retrospective cohort study was performed using linked Human Fertilisation and Embryology Authority (HFEA) data on 130 516 IVF and ICSI livebirths occurring from 103 062 women between 2000 and 2017.PARTICIPANTS/MATERIALS, SETTING, METHODSWe included women who had at least one singleton livebirth resulting from IVF/ICSI fresh embryo treatment, using their own eggs and partner’s sperm. A linked HFEA dataset was analysed using a multilevel framework, which accommodated repeated IVF cycles resulting in livebirths in the same woman. A population-averaged robust Poisson model was used for binary outcomes and a multinomial logistic regression model was used for categorical outcomes. Unadjusted and adjusted risk ratios (aRRs) (95% CI) were calculated.MAIN RESULTS AND THE ROLE OF CHANCEThere were 130 516 livebirths in 103 062 women, including 86 630 singletons, 43 886 twin births, and 5384 pairs of singleton siblings. In comparison with fresh cleavage stage ET, fresh blastocyst stage transfer in singletons was associated with a lower risk of low birthweight (aRR = 0.92; 95% CI 0.86, 0.99), lower risk of being SGA (0.83; 0.78, 0.89), and lower risk of congenital anomaly (0.79; 0.71, 0.89). This analysis did not show an increase in risk associated with preterm birth (1.00; 0.94, 1.06), high birthweight (0.99; 0.93, 1.06), LGA (0.99; 0.93, 1.05), and the chance of healthy singleton baby (1.00; 1.00, 1.02). Twins resulting from fresh blastocyst stage ET were at slightly higher risk of preterm birth (1.05; 1.02, 1.10) compared with twins conceived following fresh cleavage stage ET. There was insufficient evidence for an association with the other perinatal outcomes. Singleton siblings born following fresh blastocyst stage ET were at a higher risk of being LGA (1.57; 1.01, 2.46) and at lower risk of having a congenital anomaly (0.52; 0.28, 0.97) compared to their singleton siblings born following cleavage stage ET. There was some evidence of excess risk of preterm birth (1.42; 0.97, 2.23) associated with blastocyst stage transfer. However, we could not confirm an association between blastocyst stage ET and low birthweight (1.35; 0.81, 2.27), high birthweight (1.19; 0.80, 1.77), and the chance of being a healthy baby (0.97; 0.86, 1.09).LIMITATIONS, REASONS FOR CAUTIONThis was an observational study where we were unable to adjust for some key confounders, such as maternal smoking status and BMI, which may change from one pregnancy to another and are not recorded in the HFEA dataset.WIDER IMPLICATIONS OF THE FINDINGSIn the largest study of its kind, our analysis of singleton siblings, corrected for unmeasured, non-time varying maternal factors, confirms the previously reported association between blastocyst transfer and LGA babies, and shows a reduced risk of congenital anomaly following blastocyst transfer. Our sibling analysis did not confirm a decreased risk of low birthweight following blastocyst transfer. Overall, absolute risks are low and there is insufficient evidence to challenge the practice of extended culture of embryos.STUDY FUNDING/COMPETING INTEREST(S)This project is financed by an NHS Grampian Endowment Research Grant, project number 17/052. One of the authors, S.B., was the Editor in Chief of HROpen until 31 December 2022 and would have been in that role when the paper was first submitted. As an invited speaker, S.B. has received travel expenses, accommodation and honoraria from Merck, Organon, and Ferring. A.M. has received travel expenses, accommodation, and honoraria from Merck Serono, Cook Medical, Pharmasure, Gedeon Richter, and Ferring. D.J.M. is currently a HROpen Associate Editor.TRIAL REGISTRATION NUMBERN/A.

The thyroid is a gland located in the neck and is important for many processes in the body. Problems with the thyroid gland are common in women of reproductive age. It is essential to have a normal working thyroid gland in order to achieve a successful pregnancy. One of the most common problems with the thyroid is underactivity (known as hypothyroidism). An early, mild form of an underactive thyroid is called subclinical hypothyroidism. Often people with this condition do not have any symptoms. Another common problem is thyroid autoimmunity. Here, the immune system attacks the thyroid gland, sometimes leading to the development of abnormal thyroid function. This can be diagnosed by the presence of proteins in the bloodstream called antibodies. Mild thyroid problems and the presence of high levels of thyroid antibodies have been linked to miscarriage and premature birth. There is debate in medicine about whether there should be routine testing of thyroid function both in the general population and in individuals who are trying for a baby. In addition, the strategies used to manage certain thyroid problems are questioned. Discussions around testing and subsequent management particularly relate to women with a history of subfertility or repeated miscarriages. This Scientific Impact Paper provides information on thyroid testing and the management of mild thyroid problems and thyroid antibodies in women with a history of subfertility or recurrent miscarriages, using the latest evidence and guidelines. It concludes that there may be a role for treating these women with thyroxine tablets (the hormone produced by the thyroid gland) when subclinical hypothyroidism is present, and gives guidance on the cut-off levels for treatment.

Objective To investigate the optimal route of progesterone administration for luteal phase support in a frozen embryo transfer. Design Systematic review. Patients Women undergoing frozen embryo transfer (FET). Interventions We conducted an extensive database search of Medline (PubMed), Embase, Web of Science, and Cochrane Trials Register using relevant keywords and their combinations to find randomized controlled trials (RCTs) comparing the routes (i.e., oral, vaginal, intramuscular) of progesterone administration for luteal phase support (LPS) in artificial FET. Main outcome measures Clinical pregnancy, live birth, miscarriage. Results Four RCTs with 3245 participants undergoing artificial endometrial preparation (EP) cycles during FET were found to be eligible. Four trials compared vaginal progesterone with intramuscular progesterone and two trials compared vaginal progesterone with oral progesterone. One study favored of vaginal versus oral progesterone for clinical pregnancy rates (RR 0.45, 95% CI 0.22–0.92) and other study favored intramuscular versus vaginal progesterone for clinical pregnancy rates (RR 1.46, 95% CI 1.21–1.76) and live birth rates (RR 1.62, 95% CI 1.28–2.05). Tabulation of overall evidence strength assessment showed low-quality evidence on the basis that for each outcome-comparison pair, there were deficiencies in either directness of outcome measurement or study quality. Conclusion There was little consensus and evidence was heterogeneous on the optimal route of administration of progesterone for LPS during FET in artificial EP cycles. This warrants more trials, indirect comparisons, and network meta-analyses. PROPERO No CRD42021251017.