Abstract: Freezing all embryos, followed by thawing and transferring them into the uterine cavity at a later stage (freeze-all), instead of fresh-embryo transfer may lead to improved pregnancy rates and fewer complications during in vitro fertilisation and pregnancies resulting from it. Objective We aimed to evaluate if a policy of freeze-all results in a higher healthy baby rate than the current policy of transferring fresh embryos. Design This was a pragmatic, multicentre, two-arm, parallel-group, non-blinded, randomised controlled trial. Setting Eighteen in vitro fertilisation clinics across the UK participated from February 2016 to April 2019. Participants Couples undergoing their first, second or third cycle of in vitro fertilisation treatment in which the female partner was aged 〈  42 years. Interventions If at least three good-quality embryos were present on day 3 of embryo development, couples were randomly allocated to either freeze-all (intervention) or fresh-embryo transfer (control). Outcomes The primary outcome was a healthy baby, defined as a live, singleton baby born at term, with an appropriate weight for their gestation. Secondary outcomes included ovarian hyperstimulation, live birth and clinical pregnancy rates, complications of pregnancy and childbirth, health economic outcome, and State–Trait Anxiety Inventory scores. Results A total of 1578 couples were consented and 619 couples were randomised. Most non-randomisations were because of the non-availability of at least three good-quality embryos ( n  = 476). Of the couples randomised, 117 (19%) did not adhere to the allocated intervention. The rate of non-adherence was higher in the freeze-all arm, with the leading reason being patient choice. The intention-to-treat analysis showed a healthy baby rate of 20.3% in the freeze-all arm and 24.4% in the fresh-embryo transfer arm (risk ratio 0.84, 95% confidence interval 0.62 to 1.15). Similar results were obtained using complier-average causal effect analysis (risk ratio 0.77, 95% confidence interval 0.44 to 1.10), per-protocol analysis (risk ratio 0.87, 95% confidence interval 0.59 to 1.26) and as-treated analysis (risk ratio 0.91, 95% confidence interval 0.64 to 1.29). The risk of ovarian hyperstimulation was 3.6% in the freeze-all arm and 8.1% in the fresh-embryo transfer arm (risk ratio 0.44, 99% confidence interval 0.15 to 1.30). There were no statistically significant differences between the freeze-all and the fresh-embryo transfer arms in the live birth rates (28.3% vs. 34.3%; risk ratio 0.83, 99% confidence interval 0.65 to 1.06) and clinical pregnancy rates (33.9% vs. 40.1%; risk ratio 0.85, 99% confidence interval 0.65 to 1.11). There was no statistically significant difference in anxiety scores for male participants (mean difference 0.1, 99% confidence interval –2.4 to 2.6) and female participants (mean difference 0.0, 99% confidence interval –2.2 to 2.2) between the arms. The economic analysis showed that freeze-all had a low probability of being cost-effective in terms of the incremental cost per healthy baby and incremental cost per live birth. Limitations We were unable to reach the original planned sample size of 1086 and the rate of non-adherence to the allocated intervention was much higher than expected. Conclusion When efficacy, safety and costs are considered, freeze-all is not better than fresh-embryo transfer. Trial registration This trial is registered as ISRCTN61225414. Funding This project was funded by the National Institute for Health and Care Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment ; Vol. 26, No. 25. See the NIHR Journals Library website for further project information.

Abstract: Does a policy of elective freezing of embryos, followed by frozen embryo transfer result in a higher healthy baby rate, after first embryo transfer, when compared with the current policy of transferring fresh embryos? SUMMARY ANSWER This study, although limited by sample size, provides no evidence to support the adoption of a routine policy of elective freeze in preference to fresh embryo transfer in order to improve IVF effectiveness in obtaining a healthy baby. WHAT IS KNOWN ALREADY The policy of freezing all embryos followed by frozen embryo transfer is associated with a higher live birth rate for high responders but a similar/lower live birth after first embryo transfer and cumulative live birth rate for normal responders. Frozen embryo transfer is associated with a lower risk of ovarian hyperstimulation syndrome (OHSS), preterm delivery and low birthweight babies but a higher risk of large babies and pre-eclampsia. There is also uncertainty about long-term outcomes, hence shifting to a policy of elective freezing for all remains controversial given the delay in treatment and extra costs involved in freezing all embryos. STUDY DESIGN, SIZE, DURATION A pragmatic two-arm parallel randomized controlled trial (E-Freeze) was conducted across 18 clinics in the UK from 2016 to 2019. A total of 619 couples were randomized (309 to elective freeze/310 to fresh). The primary outcome was a healthy baby after first embryo transfer (term, singleton live birth with appropriate weight for gestation); secondary outcomes included OHSS, live birth, clinical pregnancy, pregnancy complications and cost-effectiveness. PARTICIPANTS/MATERIALS, SETTING, METHODS Couples undergoing their first, second or third cycle of IVF/ICSI treatment, with at least three good quality embryos on Day 3 where the female partner was ≥18 and & lt;42 years of age were eligible. Those using donor gametes, undergoing preimplantation genetic testing or planning to freeze all their embryos were excluded. IVF/ICSI treatment was carried out according to local protocols. Women were followed up for pregnancy outcome after first embryo transfer following randomization. MAIN RESULTS AND THE ROLE OF CHANCE Of the 619 couples randomized, 307 and 309 couples in the elective freeze and fresh transfer arms, respectively, were included in the primary analysis. There was no evidence of a statistically significant difference in outcomes in the elective freeze group compared to the fresh embryo transfer group: healthy baby rate {20.3% (62/307) versus 24.4% (75/309); risk ratio (RR), 95% CI: 0.84, 0.62 to 1.15}; OHSS (3.6% versus 8.1%; RR, 99% CI: 0.44, 0.15 to 1.30); live birth rate (28.3% versus 34.3%; RR, 99% CI 0.83, 0.65 to 1.06); and miscarriage (14.3% versus 12.9%; RR, 99% CI: 1.09, 0.72 to 1.66). Adherence to allocation was poor in the elective freeze group. The elective freeze approach was more costly and was unlikely to be cost-effective in a UK National Health Service context. LIMITATIONS, REASONS FOR CAUTION We have only reported on first embryo transfer after randomization; data on the cumulative live birth rate requires further follow-up. Planned target sample size was not obtained and the non-adherence to allocation rate was high among couples in the elective freeze arm owing to patient preference for fresh embryo transfer, but an analysis which took non-adherence into account showed similar results. WIDER IMPLICATIONS OF THE FINDINGS Results from the E-Freeze trial do not lend support to the policy of electively freezing all for everyone, taking both efficacy, safety and costs considerations into account. This method should only be adopted if there is a definite clinical indication. STUDY FUNDING/COMPETING INTEREST(S) NIHR Health Technology Assessment programme (13/115/82). This research was funded by the National Institute for Health Research (NIHR) (NIHR unique award identifier) using UK aid from the UK Government to support global health research. The views expressed in this publication are those of the author(s) and not necessarily those of the NIHR or the UK Department of Health and Social Care. J.L.B., C.C., E.J., P.H., J.J.K., L.L. and G.S. report receipt of funding from NIHR, during the conduct of the study. J.L.B., E.J., P.H., K.S. and L.L. report receipt of funding from NIHR, during the conduct of the study and outside the submitted work. A.M. reports grants from NIHR personal fees from Merck Serono, personal fees for lectures from Merck Serono, Ferring and Cooks outside the submitted work; travel/meeting support from Ferring and Pharmasure and participation in a Ferring advisory board. S.B. reports receipt of royalties and licenses from Cambridge University Press, a board membership role for NHS Grampian and other financial or non-financial interests related to his roles as Editor-in-Chief of Human Reproduction Open and Editor and Contributing Author of Reproductive Medicine for the MRCOG, Cambridge University Press. D.B. reports grants from NIHR, during the conduct of the study; grants from European Commission, grants from Diabetes UK, grants from NIHR, grants from ESHRE, grants from MRC, outside the submitted work. Y.C. reports speaker fees from Merck Serono, and advisory board role for Merck Serono and shares in Complete Fertility. P.H. reports membership of the HTA Commissioning Committee. E.J. reports membership of the NHS England and NIHR Partnership Programme, membership of five Data Monitoring Committees (Chair of two), membership of six Trial Steering Committees (Chair of four), membership of the Northern Ireland Clinical Trials Unit Advisory Group and Chair of the board of Oxford Brain Health Clinical Trials Unit. R.M. reports consulting fees from Gedeon Richter, honorarium from Merck, support fees for attendance at educational events and conferences for Merck, Ferring, Bessins and Gedeon Richter, payments for participation on a Merck Safety or Advisory Board, Chair of the British Fertility Society and payments for an advisory role to the Human Fertilisation and Embryology Authority. G.S. reports travel and accommodation fees for attendance at a health economic advisory board from Merck KGaA, Darmstadt, Germany. N.R.-F. reports shares in Nurture Fertility. Other authors’ competing interests: none declared. TRIAL REGISTRATION NUMBER ISRCTN: 61225414. TRIAL REGISTRATION DATE 29 December 2015. DATE OF FIRST PATIENT’S ENROLMENT 16 February 2016.

Abstract: To describe the prevalence of and factors associated with different thyroid dysfunction phenotypes in women who are asymptomatic preconception. Design Observational cohort study. Setting A total of 49 hospitals across the United Kingdom between 2011 and 2016. Participants Women aged 16 to 41years with history of miscarriage or subfertility trying for a pregnancy. Methods Prevalences and 95% confidence intervals (CIs) were estimated using the binomial exact method. Multivariate logistic regression analyses were conducted to identify risk factors for thyroid disease. Intervention None. Main Outcome Measure Rates of thyroid dysfunction. Results Thyroid function and thyroid peroxidase antibody (TPOAb) data were available for 19213 and 19237 women, respectively. The prevalence of abnormal thyroid function was 4.8% (95% CI, 4.5-5.1); euthyroidism was defined as levels of thyroid-stimulating hormone (TSH) of 0.44 to 4.50 mIU/L and free thyroxine (fT4) of 10 to 21 pmol/L. Overt hypothyroidism (TSH & gt; 4.50 mIU/L, fT4 & lt; 10 pmol/L) was present in 0.2% of women (95% CI, 0.1-0.3) and overt hyperthyroidism (TSH & lt; 0.44 mIU/L, fT4 & gt; 21 pmol/L) was present in 0.3% (95% CI, 0.2-0.3). The prevalence of subclinical hypothyroidism (SCH) using an upper TSH concentration of 4.50 mIU/L was 2.4% (95% CI, 2.1-2.6). Lowering the upper TSH to 2.50 mIU/L resulted in higher rates of SCH, 19.9% (95% CI, 19.3-20.5). Multiple regression analyses showed increased odds of SCH (TSH & gt; 4.50 mIU/L) with body mass index (BMI) ≥ 35.0 kg/m2 (adjusted odds ratio [aOR] 1.71; 95% CI, 1.13-2.57; P = 0.01) and Asian ethnicity (aOR 1.76; 95% CI, 1.31-2.37; P & lt; 0.001), and increased odds of SCH (TSH ≥ 2.50 mIU/L) with subfertility (aOR 1.16; 95% CI, 1.04-1.29; P = 0.008). TPOAb positivity was prevalent in 9.5% of women (95% CI, 9.1-9.9). Conclusions The prevalence of undiagnosed overt thyroid disease is low. SCH and TPOAb are common, particularly in women with higher BMI or of Asian ethnicity. A TSH cutoff of 2.50 mIU/L to define SCH results in a significant proportion of women potentially requiring levothyroxine treatment.

Abstract: Thyroid autoantibodies, specifically thyroid peroxidase antibodies, have been associated with miscarriage and pre-term birth in women with a normal thyroid function. Small randomised controlled trials have found that treatment with levothyroxine may reduce such adverse outcomes in pregnancy. Objectives The Thyroid AntiBodies and LEvoThyroxine (TABLET) trial was conducted to explore the effects of levothyroxine in euthyroid women with thyroid peroxidase antibodies. A concurrent mechanistic study was conducted to examine the effect of levothyroxine on immune responses. Design This was a randomised, double-blind, placebo-controlled, multicentre study. Setting The TABLET trial was conducted in 49 hospitals across the UK between 2011 and 2016. Participants Euthyroid women who tested positive for thyroid peroxidase antibodies, were aged between 16 and 41 years and were trying to conceive either naturally or through assisted conception were eligible. Intervention Participants were randomised to levothyroxine at a dose of 50 µg daily or placebo. The intervention was commenced preconception and continued until the end of a pregnancy. Women were given a 12-month period to conceive from randomisation. Main outcome measures The primary outcome was live birth at ≥ 34 completed weeks of gestation. The secondary outcomes included miscarriage at 〈  24 weeks; clinical pregnancy at 7 weeks; ongoing pregnancy at 12 weeks; gestation at delivery; birthweight; appearance, pulse, grimace, activity and respiration (Apgar) scores; congenital abnormalities; and neonatal survival at 28 days of life. Methods Participants were randomised in a 1 : 1 ratio. Minimisation was implemented for age ( 〈  35 or ≥ 35 years), number of previous miscarriages (0, 1 or 2, ≥ 3), infertility treatment (yes/no) and baseline thyroid-stimulating hormone concentration (≤ 2.5 or 〉  2.5 mlU/l) to achieve balanced trial arms. Women were followed up every 3 months while trying to conceive to check thyroid function and general well-being, and, once pregnant, were seen each trimester: 6–8 weeks, 16–18 weeks and 28 weeks. Any abnormal thyroid results were managed in line with clinical guidance at the time. Results Of the 19,556 women screened, 1420 women were eligible and 952 were randomised to receive levothyroxine ( n  = 476) or placebo ( n  = 476). Six women from each arm either were lost to follow-up or withdrew from the trial. A total 540 women became pregnant: 266 in the levothyroxine arm and 274 in the placebo arm. The live birth rate was 37% (176/470) in the levothyroxine group and 38% (178/470) in the placebo group, translating to a relative risk of 0.97 (95% confidence interval 0.83 to 1.14; p  = 0.74) and an absolute risk difference of –0.4% (95% confidence interval –6.6% to 5.8%). A subset of 49 trial participants (26 in the levothyroxine arm and 23 in the placebo arm) were recruited to assess changes in their serum chemocytokine concentrations. Treatment with levothyroxine resulted in some changes in chemocytokine concentrations in the non-pregnant state and in early pregnancy, but these had no association with clinical outcome. Conclusions Levothyroxine therapy in a dose of 50 µg per day does not improve live birth rate in euthyroid women with thyroid peroxidase antibodies. Limitations Titration of the levothyroxine dose based on thyroid-stimulating hormone/thyroid peroxidase concentrations was not explored. Future work Future research could explore the efficacy of levothyroxine administered for the treatment of subclinical hypothyroidism. Trial registration Current Controlled Trials ISRCTN15948785 and EudraCT 2011-000719-19. Funding This project was funded by the Efficacy and Mechanism Evaluation programme, a Medical Research Council and National Institute for Health Research partnership.