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Competing Interests: Declaration of Interests L.B. has nothing to disclose. M.S. has nothing to disclose. W.C. has nothing to disclose. K.D. has nothing to disclose. P.A.R. has nothing to disclose.

Study Question: Does BMI of gestational carriers (GCs) affect perinatal outcomes after embryo transfer?, Summary Answer: Overweight and class I obesity in GCs does not affect the rate of good perinatal outcomes., What Is Known Already: The use of GCs is increasing, but uniform guidance regarding optimal BMI for GCs is lacking. Women with obesity who conceive without fertility treatment or through autologous or donor in vitro fertilization are at higher risk of adverse maternal and fetal outcomes, but data on obesity in GCs are very limited., Study Design, Size, Duration: We performed a retrospective cohort study of 1121 GC cycles from January 2015 to December 2020 at US Fertility, the largest national partnership of fertility practices in the USA., Participants/materials, Setting, and Methods: All GC cycles performed at a large network of fertility practices were reviewed. Same-sex partners undergoing co-IVF were excluded. The primary outcome was good perinatal outcome from the first embryo transfer, defined as a singleton live birth at ≥37 weeks of gestation with birth weight between 2500 and 4000 g. Secondary outcome measures included frequencies of live birth, clinical pregnancy, miscarriage, full-term birth, low birth weight, large for gestational age, and cesarean delivery. A generalized linear model (log-binomial) was used for each to compare outcomes across BMI groups using normal BMI (20-24.9 kg/m2) as the reference group. Risk ratios and 95% CIs were estimated for each category group relative to normal BMI., Main Results and the Role of Chance: We identified 1121 cycles in which GCs underwent first embryo transfer, of which 263 (23.5%) were in GCs with BMI >30. Demographics and reproductive history for GCs did not differ by BMI groups. The age of intended parents, use of frozen eggs, and fresh embryo transfers were higher with increasing BMI group. There were no statistically significant associations between BMI and good perinatal outcomes, live birth, clinical pregnancy, biochemical, spontaneous abortion, or low birth weight. However, among live births, higher BMI was significantly associated with birth by cesarean (P = 0.015) and large for gestational age infants (P = 0.023)., Limitations, Reasons for Caution: This was a retrospective study, and there may be unmeasured confounders. The number of patients with BMI <20 or ≥35 was small, limiting the power for these groups. We were not able to assess all maternal and fetal outcomes., Wider Implications of the Findings: In this study, we did not identify any significant impact of BMI on the chances of having a good perinatal outcome. Prior research studies have been inconsistent and this is the largest study to date., Study Funding/competing Interest(s): No external funding was received for this work. The authors do not have any conflicts of interest to declare., Trial Registration Number: N/A., (© The Author(s) 2024. Published by Oxford University Press on behalf of European Society of Human Reproduction and Embryology. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Purpose: There is an unclear relationship between estradiol levels and fresh embryo transfer (ET) outcomes. We determined the relationship between estradiol on the day of trigger, in fresh ET cycles without premature progesterone elevation, and good birth outcomes (GBO)., Methods: We identified autologous fresh ET cycles from 2015 to 2021 at multiple clinics in the USA. Patients with recurrent pregnancy loss, uterine factor, and elevated progesterone on the day of trigger (progesterone > 2 ng/mL or 3-day area under the curve > 4.5 ng/mL) were excluded. The primary outcome was GBO (singleton, term, live birth with appropriate weight). Log-binomial generalized estimating equations determined the likelihood of outcomes., Results: Of 17,608 fresh ET cycles, 5025 (29%) yielded GBO. Cycles with estradiol ≥ 4000 pg/mL had a greater likelihood of GBO compared to cycles < 1000 pg/mL (aRR = 1.32, 95% CI 1.13-1.54). Pairwise comparisons of estradiol between < 1000 pg/mL versus 1000-1999 pg/mL and 1000-1999 pg/mL versus 2000-2999 pg/mL revealed a higher likelihood of GBO with higher estradiol (aRR 0.83, 95% CI 0.73-0.95; aRR 0.91, 95% CI 0.85-0.97, respectively). Comparisons amongst more elevated estradiol levels revealed that the likelihood of GBO remained similar between groups (2000-2999 pg/mL versus 3000-3999 pg/mL, aRR 1.04, 95% CI 0.97-1.11; 3000-3999 pg/mL versus ≥ 4000 pg/mL, aRR 0.96, 95% CI 0.9-1.04)., Conclusion: In fresh ET cycles, higher estradiol levels were associated with an increased prevalence of GBO until estradiol 2000-2999 pg/mL, thereafter plateauing. In fresh ET candidates, elevated estradiol levels should not preclude eligibility though premature progesterone rise, and risk of ovarian hyperstimulation syndrome must still be considered., (© 2024. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Importance: Endometrial receptivity testing is purported to improve live birth following frozen embryo transfer by identifying the optimal embryo transfer time for an individual patient; however, data are conflicting., Objective: To compare live birth from single euploid frozen embryo transfer according to endometrial receptivity testing vs standardized timing., Design, Setting, and Participants: Double-blind, randomized clinical trial at 30 sites within a multicenter private fertility practice in the Eastern US. Enrollment was from May 2018 to September 2020; follow-up concluded in August 2021. Participants underwent in vitro fertilization, preimplantation genetic testing for aneuploidy, endometrial receptivity testing, and frozen embryo transfer. Those with euploid blastocyst(s) and an informative receptivity result were randomized. Exclusion criteria included recurrent pregnancy loss, recurrent implantation failure, surgically aspirated sperm, donor egg(s), and unmitigated anatomic uterine cavity defects., Interventions: The intervention group (n = 381) underwent receptivity-timed frozen embryo transfer, with adjusted duration of progesterone exposure prior to transfer, if indicated by receptivity testing. The control group (n = 386) underwent transfer at standard timing, regardless of receptivity test results., Main Outcomes and Measures: The primary outcome was live birth. There were 3 secondary outcomes, including biochemical pregnancy and clinical pregnancy., Results: Among 767 participants who were randomized (mean age, 35 years), 755 (98%) completed the trial. All randomized participants were analyzed. The primary outcome of live birth occurred in 58.5% of transfers (223 of 381) in the intervention group vs 61.9% of transfers (239 of 386) in the control group (difference, -3.4% [95% CI, -10.3% to 3.5%]; rate ratio [RR], 0.95 [95% CI, 0.79 to 1.13]; P = .38). There were no significant differences in the intervention vs the control group for the prespecified secondary outcomes, including biochemical pregnancy rate (77.2% vs 79.5%, respectively; difference, -2.3% [95% CI, -8.2% to 3.5%]; RR, 0.97 [95% CI, 0.83 to 1.14]; P = .48) and clinical pregnancy rate (68.8% vs 72.8%, respectively; difference, -4.0% [95% CI, -10.4% to 2.4%]; RR, 0.94 [95% CI, 0.80 to 1.12]; P = .25). There were no reported adverse events., Conclusions and Relevance: Among patients for whom in vitro fertilization yielded a euploid blastocyst, the use of receptivity testing to guide the timing of frozen embryo transfer, compared with standard timing for transfer, did not significantly improve the rate of live birth. The findings do not support routine use of receptivity testing to guide the timing of embryo transfer during in vitro fertilization., Trial Registration: ClinicalTrials.gov Identifier: NCT03558399.

Objective: To determine whether endometrial receptivity analysis (ERA) improves live births in patients with and without a history of unsuccessful frozen embryo transfers (FETs)., Design: Retrospective cohort study., Setting: Large reproductive center., Patient(s): Patients with and without ERA before euploid single FET were included in the analysis., Intervention(s): Subjects in the exposed group underwent ERA and ERA-timed FETs. Subjects in the unexposed group followed a standard protocol FET without ERA. Outcomes were compared between nonreceptive and receptive subjects undergoing an ERA-timed FET and between ERA-timed vs. standard protocol FETs., Main Outcome Measure(s): The primary outcome was a live birth; secondary outcomes were biochemical and clinical pregnancy rates., Result(s): A total of 307 ERA-timed FETs and 2,284 standard protocol FETs were analyzed. One hundred twenty-five patients (40.7%) were ERA receptive, and 182 (59.3%) were ERA nonreceptive. After adjusting for the number of the previously failed FETs, there was no difference in the proportion of receptive and nonreceptive ERA results. There were no statistically significant differences in live births in patients with ERA-receptive vs. ERA-nonreceptive results (48.8% and 41.7%, respectively; adjusted odds ratio 1.17; 95% CI, 0.97-1.40). There were no statistically significant differences in live births in patients with or without ERA testing results before FET (44.6% and 51.3%, respectively; adjusted odds ratio 0.87; 95% CI, 0.73-1.04)., Conclusion(s): Patients with an increasing number of previous failed euploid FET cycles are not at an increased risk of a displaced window of implantation. Patients categorized as receptive vs. nonreceptive and those without ERA testing results have comparable FET success rates., (Copyright © 2022 American Society for Reproductive Medicine. Published by Elsevier Inc. All rights reserved.)

Background: Randomized trials of assisted reproductive technology (ART) have been designed for outcomes of clinical pregnancy or live birth and have not been powered for obstetric outcomes such as preeclampsia, critical for maternal and fetal health. ART increasingly involves frozen embryo transfer (FET). Although there are advantages of FET, multiple studies have shown that risk of preeclampsia is increased with FET compared with fresh embryo transfer, and the reason for this difference is not clear. NatPro will compare the proportion of preeclampsia between two commonly used protocols for FET,modified natural and programmed cycle., Methods: In this two-arm, parallel-group, multi-center randomized trial, NatPro will randomize 788 women to either modified natural or programmed FET and follow them for up to three FET cycles. Primary outcome will be the proportion of preeclampsia in women with a viable pregnancy assigned to a modified natural cycle FET (corpus luteum present) protocol compared to the proportion of preeclampsia in pregnant women assigned to a programmed FET (corpus luteum absent) protocol. Secondary outcomes will compare the proportion of live births and the proportion of preeclampsia with severe features between the protocols., Conclusion: This study has a potential significant impact on millions of women who pursue ART to build their families. NatPro is designed to provide clinically relevant guidance to inform patients and clinicians regarding maternal risk with programmed and modified natural cycle FET protocols. This study will also provide accurate point estimates regarding the likelihood of live birth with programmed and modified natural cycle FET., Trial Registration: ClinicalTrials.gov NCT04551807 . Registered on September 16, 2020., (© 2021. The Author(s).)

Objective: To determine whether vaginal progesterone for programmed endometrial preparation is noninferior to intramuscular progesterone in terms of live birth rates from frozen embryo transfer (FET)., Design: Three-armed, randomized, controlled noninferiority trial., Setting: Multicenter fertility clinic., Patient(s): A total of 1,346 volunteer subjects planning vitrified-warmed transfer of high-quality nonbiopsied blastocysts were screened, of whom 1,125 subjects were ultimately enrolled and randomly assigned to treatment., Intervention(s): The subjects were randomly assigned to receive, in preparation for FET, 50 mg daily of intramuscular progesterone (control group), 200 mg twice daily of vaginal micronized progesterone plus 50 mg of intramuscular progesterone every third day (combination treatment), or 200 mg twice daily of vaginal micronized progesterone., Main Outcome Measure(s): The primary outcome was live birth rate per vitrified-warmed embryo transfer. The secondary outcomes were a positive serum human chorionic gonadotropin test 2 weeks after FET, biochemical pregnancy loss, clinical pregnancy, clinical pregnancy loss, total pregnancy loss, serum luteal progesterone concentration 2 weeks after FET, and patient's experience and attitudes regarding the route of progesterone administration, on the basis of a survey administered to the subjects between FET and pregnancy test., Result(s): A total of 1,060 FETs were completed. The live birth rate was significantly lower in women receiving only vaginal progesterone (27%) than in women receiving intramuscular progesterone (44%) or combination treatment (46%). Fifty percent of pregnancies in women receiving only vaginal progesterone ended in miscarriage., Conclusion(s): The live birth rate after vaginal-only progesterone replacement was significantly reduced, due primarily to an increased rate of miscarriage. Vaginal progesterone supplemented with intramuscular progesterone every third day was noninferior to daily intramuscular progesterone, offering an effective alternative regimen with fewer injections., Clinical Trial Registration Number: NCT02254577., (Copyright © 2021 American Society for Reproductive Medicine. Published by Elsevier Inc. All rights reserved.)

Objective: To determine whether subfertility in patients with endometriosis is due to impaired endometrial receptivity by comparing pregnancy and live-birth outcomes in women with endometriosis versus two control groups without suspected endometrial factors: noninfertile patients who underwent assisted reproduction to test embryos for a single-gene disorder and couples with isolated male factor infertility., Design: Retrospective cohort., Setting: Multicenter private practice., Patient(s): All patients aged 24 to 44 years undergoing euploid frozen blastocysts transfer from January 2016 through March 2018., Intervention(s): None., Main Outcome Measure(s): Live birth, clinical pregnancies, pregnancy losses, and aneuploid rates in preimplantation genetic testing for aneuploidy cycles., Result(s): The analysis included 459 euploid frozen embryo transfer cycles among 328 unique patients. There were no differences in clinical pregnancy, pregnancy loss, or live-birth rates in patients with endometriosis compared with both control groups. The aneuploidy rates were lowest in the preimplantation genetic testing for monogenic disorders cohort, and the endometriosis patients had aneuploidy rates similar to those of the male factor infertility patients., Conclusion(s): It is unclear whether endometriosis primarily affects in vitro fertilization outcomes via oocyte quality or the endometrium. By controlling for embryo quality using euploid frozen embryo transfer cycles, we found no difference in pregnancy outcomes in patients with endometriosis compared with patients undergoing treatment for male factor infertility and noninfertile patients., (Copyright © 2020. Published by Elsevier Inc.)

Objective: To determine if transferring a lower-quality embryo with a good-quality blastocyst is detrimental, given that evidence suggests that embryos can signal the endometrium and that embryo quality may affect negatively endometrial receptivity., Design: Retrospective cohort study., Setting: In vitro fertilization center., Intervention(s): Single- versus double-embryo transfer., Patient(s): Patients with a double-embryo transfer of a good-quality blastocyst plus a lower-quality blastocyst, early blastocyst, or morula were compared with patients receiving a single good-quality blastocyst., Main Outcome Measure(s): Live birth, multiple gestation., Result(s): In this study, 4,640 in vitro fertilization cycles were analyzed. In none of the analyses did transferring a second lower-quality embryo negatively affect birth rate. In the primary analysis, transferring a second lower-quality embryo increased live birth by 10% and the multiple birth rate by 15%. The addition of a fair- or poor-quality blastocyst or early blastocyst markedly increased the twin birth rate by 22%-27% with an 8%-12% increase in live birth. The addition of a morula did not increase live birth but resulted in 12% more multiples. In women younger than 38 years, adding a lower-quality embryo increased the birth rate by 7% but resulted in 18% increase in multiples. In women 38 years or older, adding a lower-quality embryo increased the live birth rate by 9% with a 15% increase in multiples., Conclusion(s): Addition of a lower-quality embryo does not have a detrimental effect on a good-quality blastocyst and results in a small increase in live births. However, this is at the expense of a marked increase in the likelihood of multiple gestations., (Published by Elsevier Inc.)

Objective: To assess the noninferiority of vaginal P (Endometrin) compared with daily intramuscular P for replacement in programmed vitrified-warmed blastocyst transfer cycles and to assess the noninferiority of vaginal P in combination with intramuscular progesterone every third day compared with daily intramuscular P., Design: Three-arm randomized controlled noninferiority study. To enable early recognition of inferiority if present, an a priori interim analysis was planned and completed once ongoing pregnancy data were available for 50% of the total enrollment goal. The results of this interim analysis are presented here., Setting: Assisted reproduction technology practice., Patient(s): Women undergoing transfer of nonbiopsied high quality vitrified-warmed blastocyst(s) in a programmed cycle., Intervention(s): Vitrified-warmed blastocyst transfer with mode of P replacement determined by randomization to either: (1) 50 mg daily intramuscular P only; (2) 200 mg twice daily vaginal Endometrin; or (3) 200 mg twice daily Endometrin plus 50 mg intramuscular P every 3rd day., Main Outcome Measure(s): Live birth. The primary outcome of this interim analysis was ongoing pregnancy., Result(s): A total of 645 cycles were randomly assigned to one of the three treatment arms, received at least one dose of P replacement therapy according to this assignment and underwent vitrified-warmed blastocyst transfer. These cycles were included in the intention-to-treat analysis. The study team, including the statistician, were blinded to the identity of the treatment arms, which were randomly labeled "A," "B," and "C" in the dataset. Ongoing pregnancy occurred in 50%, 47%, and 31% of cycles in arms A, B, and C respectively. Although arm C had an rate of positive hCG equivalent to the other two arms, the rate of pregnancy loss for arm C was significantly higher than for either of the two arms, resulting in a more than one-third lower rate of ongoing pregnancy. There were no statistically significant differences for any outcome tested between arms A and B. Results of a per-protocol analysis were nearly identical to those of the intention-to-treat analysis. On completion of these analyses, arm C was revealed to be the vaginal P only arm., Conclusion(s): Relative to regimens inclusive of intramuscular P, vaginal-only P replacement for vitrified-warmed blastocyst transfer results in decreased ongoing pregnancy, due to increased miscarriage, and should be avoided. Randomization to the vaginal-only arm was terminated with these findings. This trial is ongoing to assess the noninferiority of the vaginal plus every 3rd day intramuscular P arm compared with daily intramuscular P in terms of live birth., Clinical Trial Registration Number: NLM identifier NCT02254577., (Copyright © 2017 American Society for Reproductive Medicine. Published by Elsevier Inc. All rights reserved.)

Recent evidence has shown elevated progesterone (P) advances the endometrium in fresh ART cycles, creating asynchrony with the embryo and thus implantation failure and decreased live birth rates. If the window of implantation is closing as the embryo attempts to implant, there may be difficulty with trophoblastic invasion, leading to failure of early pregnancies. Our objective was to evaluate if P on the day of trigger was associated with spontaneous abortion (SAB) rates in fresh ART transfers. This was a retrospective cohort study involving fresh autologous and FET cycles from 2011 to 2013. The main outcome was spontaneous abortion rates. About 4123 fresh and FET transfer cycles were included which resulted in 1547 fresh and 491 FET pregnancies. The overall SAB rate was 20% among fresh cycles and 19% in FET cycles. P on the day of trigger, as a continuous variable or when > 2 ng/mL, was not associated with SAB in fresh cycles. Similar results were found after adjusting for age, embryo quality, and embryo stage. Despite elevated P likely advancing the window of implantation, once implantation occurs, pregnancies were no longer negatively impacted by progesterone.

Objective: To compare the effect of progesterone (P) on the day of trigger in fresh assisted reproduction technology (ART) transfer cycles versus its effect on subsequent frozen embryo transfer (FET) cycles., Design: Retrospective cohort study., Setting: Large private ART practice., Patient(s): Fresh autologous and FET cycles from 2011-2013., Intervention(s): None., Main Outcome Measure(s): Live birth., Result(s): A paired analysis of patients who underwent both a fresh transfer and subsequent FET cycle and an unpaired analysis of data from all fresh transfer cycles and all FET cycles were performed. We analyzed 1,216 paired and 4,124 unpaired cycles, and P was negatively associated with birth in fresh but not FET cycles in all analyses. Interaction testing of P and cycle type indicated P had a different association with birth in fresh versus FET cycles. When P was ≥ 2 ng/mL at the time of trigger, live birth was more likely in FET versus fresh cycles in the paired analysis (47% vs. 10%), in the unpaired analysis (51% vs. 14%), and in unpaired, good blastocyst only transfer subgroup (51% vs. 29%). Live birth was similar in FET cycles, with P ≥ 2 ng/mL versus P < 2 ng/mL (51% vs. 49%). Conversely, live birth was lower in fresh cycles, with P ≥ 2 ng/mL versus P <2 ng/mL (15% vs. 45%)., Conclusion(s): Elevated P levels on the day of trigger during the initial fresh cycle were negatively associated with live birth in the fresh transfer cycles but not in subsequent FET cycles. Freezing embryos and performing a subsequent FET cycle ameliorates the effect of elevated P on live-birth rates., (Published by Elsevier Inc.)

Objective: To compare live-birth rates, blastocyst to live-birth efficiency, gestational age, and birth weights in a large cohort of patients undergoing single versus double thawed blastocyst transfer., Design: Retrospective cohort study., Setting: Assisted reproduction technology (ART) practice., Patient(s): All autologous frozen blastocyst transfers (FBT) of one or two vitrified-warmed blastocysts from January 2009 through April 2012., Intervention(s): Single or double FBT., Main Outcome Measure(s): Live birth, blastocyst to live-birth efficiency, preterm birth, low birth weight., Result(s): Only supernumerary blastocysts with good morphology (grade BB or better) were vitrified, and 1,696 FBTs were analyzed. No differences were observed in patient age, rate of embryo progression, or postthaw blastomere survival. Double FBT yielded a higher live birth per transfer, but 33% of births from double FBT were twins versus only 0.6% of single FBT. Double FBT was associated with statistically significant increases in preterm birth and low birth weight, the latter of which was statistically significant even when the analysis was limited to singletons. Of the blastocysts transferred via single FBT, 38% resulted in a liveborn child versus only 34% with double FBT. This suggests that two single FBTs would result in more liveborn children with significantly fewer preterm births when compared with double FBT., Conclusion(s): Single FBT greatly decreased multiple and preterm birth risk while providing excellent live-birth rates. Patients should be counseled that a greater overall number of live born children per couple can be expected when thawed blastocysts are transferred one at a time., (Published by Elsevier Inc.)