Human embryonic stem cells derived by somatic cell nuclear transfer.

Reprogramming somatic cells into pluripotent embryonic stem cells (ESCs) by somatic cell nuclear transfer (SCNT) has been envisioned as an approach for generating patient-matched nuclear transfer (NT)-ESCs for studies of disease mechanisms and for developing specific therapies. Past attempts to produce human NT-ESCs have failed secondary to early embryonic arrest of SCNT embryos. Here, we identified premature exit from meiosis in human oocytes and suboptimal activation as key factors that are responsible for these outcomes. Optimized SCNT approaches designed to circumvent these limitations allowed derivation of human NT-ESCs. When applied to premium quality human oocytes, NT-ESC lines were derived from as few as two oocytes. NT-ESCs displayed normal diploid karyotypes and inherited their nuclear genome exclusively from parental somatic cells. Gene expression and differentiation profiles in human NT-ESCs were similar to embryo-derived ESCs, suggesting efficient reprogramming of somatic cells to a pluripotent state.

Author Correction: Mitochondrial replacement in human oocytes carrying pathogenic mitochondrial DNA mutations.

Change history In this Letter, there are several errors regarding the assignments of mtDNA haplotypes for a subset of egg donors from our study. These errors have not been corrected online.

Fertility Treatment and Preservation Options for Transgender and Gender Diverse People.

Years of growing research demonstrate that transgender and gender diverse (TGD) people desire fertility counseling and family building, however social and medical factors can impact future fertility options. Fortunately, TGD individuals have many viable options for family building using their own gametes and/or reproductive organs. However, the nuanced ways in which different gender affirming treatments affect reproduction, the interplay with non-treatment related infertility factors, and mitigation of likely dysphoria triggers are all critical to actual utilization. This review focuses on fertility treatment and preservation options for TGD patients and highlights these influential social and medical factors. Fertility treatments may be associated with worsening gender dysphoria in TGD people, and an affirming clinical environment and conscientious provider approach is paramount to treatment success. However, reducing gender dysphoria can also require specific changes to medically assisted reproduction and sperm collection protocols, some which carry the potential for diminished outcomes or unknown effects. Adolescents undergoing fertility preservation treatments may need more support or additional protocol modifications, and outcomes may be poorer in this age group compared with adults. Testicular and ovarian tissue cryopreservation may present a fertility preservation option for prepubertal TGD children, however in-vitro gamete maturation remains experimental in this situation.

Correction of a pathogenic gene mutation in human embryos.

Genome editing has potential for the targeted correction of germline mutations. Here we describe the correction of the heterozygous MYBPC3 mutation in human preimplantation embryos with precise CRISPR-Cas9-based targeting accuracy and high homology-directed repair efficiency by activating an endogenous, germline-specific DNA repair response. Induced double-strand breaks (DSBs) at the mutant paternal allele were predominantly repaired using the homologous wild-type maternal gene instead of a synthetic DNA template. By modulating the cell cycle stage at which the DSB was induced, we were able to avoid mosaicism in cleaving embryos and achieve a high yield of homozygous embryos carrying the wild-type MYBPC3 gene without evidence of off-target mutations. The efficiency, accuracy and safety of the approach presented suggest that it has potential to be used for the correction of heritable mutations in human embryos by complementing preimplantation genetic diagnosis. However, much remains to be considered before clinical applications, including the reproducibility of the technique with other heterozygous mutations.

Mitochondrial replacement in human oocytes carrying pathogenic mitochondrial DNA mutations.

Maternally inherited mitochondrial (mt)DNA mutations can cause fatal or severely debilitating syndromes in children, with disease severity dependent on the specific gene mutation and the ratio of mutant to wild-type mtDNA (heteroplasmy) in each cell and tissue. Pathogenic mtDNA mutations are relatively common, with an estimated 778 affected children born each year in the United States. Mitochondrial replacement therapies or techniques (MRT) circumventing mother-to-child mtDNA disease transmission involve replacement of oocyte maternal mtDNA. Here we report MRT outcomes in several families with common mtDNA syndromes. The mother's oocytes were of normal quality and mutation levels correlated with those in existing children. Efficient replacement of oocyte mutant mtDNA was performed by spindle transfer, resulting in embryos containing >99% donor mtDNA. Donor mtDNA was stably maintained in embryonic stem cells (ES cells) derived from most embryos. However, some ES cell lines demonstrated gradual loss of donor mtDNA and reversal to the maternal haplotype. In evaluating donor-to-maternal mtDNA interactions, it seems that compatibility relates to mtDNA replication efficiency rather than to mismatch or oxidative phosphorylation dysfunction. We identify a polymorphism within the conserved sequence box II region of the D-loop as a plausible cause of preferential replication of specific mtDNA haplotypes. In addition, some haplotypes confer proliferative and growth advantages to cells. Hence, we propose a matching paradigm for selecting compatible donor mtDNA for MRT.

Germline transmission of donor, maternal and paternal mtDNA in primates.

STUDY QUESTION: What are the long-term developmental, reproductive and genetic consequences of mitochondrial replacement therapy (MRT) in primates? SUMMARY ANSWER: Longitudinal investigation of MRT rhesus macaques (Macaca mulatta) generated with donor mtDNA that is exceedingly distant from the original maternal counterpart suggest that their growth, general health and fertility is unremarkable and similar to controls. WHAT IS KNOWN ALREADY: Mitochondrial gene mutations contribute to a diverse range of incurable human disorders. MRT via spindle transfer in oocytes was developed and proposed to prevent transmission of pathogenic mtDNA mutations from mothers to children. STUDY DESIGN, SIZE, DURATION: The study provides longitudinal studies on general health, fertility as well as transmission and segregation of parental mtDNA haplotypes to various tissues and organs in five adult MRT rhesus macaques and their offspring. PARTICIPANTS/MATERIALS, SETTING, METHODS: MRT was achieved by spindle transfer between metaphase II oocytes from genetically divergent rhesus macaque populations. After fertilization of oocytes with sperm, heteroplasmic zygotes contained an unequal mixture of three parental genomes, i.e. donor (≥97%), maternal (≤3%), and paternal (≤0.1%) mitochondrial (mt)DNA. MRT monkeys were grown to adulthood and their development and general health was regularly monitored. Reproductive fitness of male and female MRT macaques was evaluated by time-mated breeding and production of live offspring. The relative contribution of donor, maternal, and paternal mtDNA was measured by whole mitochondrial genome sequencing in all organs and tissues of MRT animals and their offspring. MAIN RESULTS AND THE ROLE OF CHANCE: Both male and female MRT rhesus macaques containing unequal mixture of three parental genomes, i.e. donor (≥97%), maternal (≤3%), and paternal (≤0.1%) mtDNA reached healthy adulthood, were fertile and most animals stably maintained the initial ratio of parental mtDNA heteroplasmy and donor mtDNA was transmitted from females to offspring. However, in one monkey out of four analyzed, initially negligible maternal mtDNA heteroplasmy levels increased substantially up to 17% in selected internal tissues and organs. In addition, two monkeys showed paternal mtDNA contribution up to 33% in selected internal tissues and organs. LARGE SCALE DATA: N/A. LIMITATIONS, REASONS FOR CAUTION: Conclusions in this study were made on a relatively low number of MRT monkeys, and on only one F1 (first generation) female. In addition, monkey MRT involved two wildtype mtDNA haplotypes, but not disease-relevant variants. Clinical trials on children born after MRT will be required to fully determine safety and efficacy of MRT for humans. WIDER IMPLICATIONS OF THE FINDINGS: Our data show that MRT is compatible with normal postnatal development including overall health and reproductive fitness in nonhuman primates without any detected adverse effects. 'Mismatched' donor mtDNA in MRT animals even from the genetically distant mtDNA haplotypes did not cause secondary mitochondrial dysfunction. However, carry-over maternal or paternal mtDNA contributions increased substantially in selected internal tissues / organs of some MRT animals implying the possibility of mtDNA mutation recurrence. STUDY FUNDING/COMPETING INTEREST(S): This work has been funded by the grants from the Burroughs Wellcome Fund, the National Institutes of Health (RO1AG062459 and P51 OD011092), National Research Foundation of Korea (2018R1D1A1B07043216) and Oregon Health & Science University institutional funds. The authors declare no competing interests.

Metabolic rescue in pluripotent cells from patients with mtDNA disease.

Mitochondria have a major role in energy production via oxidative phosphorylation, which is dependent on the expression of critical genes encoded by mitochondrial (mt)DNA. Mutations in mtDNA can cause fatal or severely debilitating disorders with limited treatment options. Clinical manifestations vary based on mutation type and heteroplasmy (that is, the relative levels of mutant and wild-type mtDNA within each cell). Here we generated genetically corrected pluripotent stem cells (PSCs) from patients with mtDNA disease. Multiple induced pluripotent stem (iPS) cell lines were derived from patients with common heteroplasmic mutations including 3243A>G, causing mitochondrial encephalomyopathy and stroke-like episodes (MELAS), and 8993T>G and 13513G>A, implicated in Leigh syndrome. Isogenic MELAS and Leigh syndrome iPS cell lines were generated containing exclusively wild-type or mutant mtDNA through spontaneous segregation of heteroplasmic mtDNA in proliferating fibroblasts. Furthermore, somatic cell nuclear transfer (SCNT) enabled replacement of mutant mtDNA from homoplasmic 8993T>G fibroblasts to generate corrected Leigh-NT1 PSCs. Although Leigh-NT1 PSCs contained donor oocyte wild-type mtDNA (human haplotype D4a) that differed from Leigh syndrome patient haplotype (F1a) at a total of 47 nucleotide sites, Leigh-NT1 cells displayed transcriptomic profiles similar to those in embryo-derived PSCs carrying wild-type mtDNA, indicative of normal nuclear-to-mitochondrial interactions. Moreover, genetically rescued patient PSCs displayed normal metabolic function compared to impaired oxygen consumption and ATP production observed in mutant cells. We conclude that both reprogramming approaches offer complementary strategies for derivation of PSCs containing exclusively wild-type mtDNA, through spontaneous segregation of heteroplasmic mtDNA in individual iPS cell lines or mitochondrial replacement by SCNT in homoplasmic mtDNA-based disease.

Deleterious mtDNA mutations are common in mature oocytes.

Heritable mitochondrial DNA (mtDNA) mutations are common, yet only a few recurring pathogenic mtDNA variants account for the majority of known familial cases in humans. Purifying selection in the female germline is thought to be responsible for the elimination of most harmful mtDNA mutations during oogenesis. Here we show that deleterious mtDNA mutations are abundant in ovulated mature mouse oocytes and preimplantation embryos recovered from PolG mutator females but not in their live offspring. This implies that purifying selection acts not in the maternal germline per se, but during post-implantation development. We further show that oocyte mtDNA mutations can be captured and stably maintained in embryonic stem cells and then reintroduced into chimeras, thereby allowing examination of the effects of specific mutations on fetal and postnatal development.

Abnormalities in human pluripotent cells due to reprogramming mechanisms.

Human pluripotent stem cells hold potential for regenerative medicine, but available cell types have significant limitations. Although embryonic stem cells (ES cells) from in vitro fertilized embryos (IVF ES cells) represent the 'gold standard', they are allogeneic to patients. Autologous induced pluripotent stem cells (iPS cells) are prone to epigenetic and transcriptional aberrations. To determine whether such abnormalities are intrinsic to somatic cell reprogramming or secondary to the reprogramming method, genetically matched sets of human IVF ES cells, iPS cells and nuclear transfer ES cells (NT ES cells) derived by somatic cell nuclear transfer (SCNT) were subjected to genome-wide analyses. Both NT ES cells and iPS cells derived from the same somatic cells contained comparable numbers of de novo copy number variations. In contrast, DNA methylation and transcriptome profiles of NT ES cells corresponded closely to those of IVF ES cells, whereas iPS cells differed and retained residual DNA methylation patterns typical of parental somatic cells. Thus, human somatic cells can be faithfully reprogrammed to pluripotency by SCNT and are therefore ideal for cell replacement therapies.

Towards germline gene therapy of inherited mitochondrial diseases.

Mutations in mitochondrial DNA (mtDNA) are associated with severe human diseases and are maternally inherited through the egg's cytoplasm. Here we investigated the feasibility of mtDNA replacement in human oocytes by spindle transfer (ST; also called spindle-chromosomal complex transfer). Of 106 human oocytes donated for research, 65 were subjected to reciprocal ST and 33 served as controls. Fertilization rate in ST oocytes (73%) was similar to controls (75%); however, a significant portion of ST zygotes (52%) showed abnormal fertilization as determined by an irregular number of pronuclei. Among normally fertilized ST zygotes, blastocyst development (62%) and embryonic stem cell isolation (38%) rates were comparable to controls. All embryonic stem cell lines derived from ST zygotes had normal euploid karyotypes and contained exclusively donor mtDNA. The mtDNA can be efficiently replaced in human oocytes. Although some ST oocytes displayed abnormal fertilization, remaining embryos were capable of developing to blastocysts and producing embryonic stem cells similar to controls.

Unhealthy air quality secondary to wildfires is associated with lower blastocyst yield.

OBJECTIVE: To study the impact of unhealthy air quality from the 2020 Oregon wildfires on outcomes for patients undergoing in vitro fertilization (IVF) treatment. DESIGN: A retrospective cohort study. SETTING: A university-based fertility clinic. PATIENTS: Subjects were undergoing IVF treatment from the 6 weeks preceding the wildfires through a 10-day exposure period. Cohorts were classified on the basis of whether subjects experienced patient and/or laboratory exposure to unhealthy air quality. Patient exposure was defined as at least 4 days of ovarian stimulation overlapping with the exposure, and laboratory exposure was defined as at least 2 days of IVF treatment and embryogenesis overlapping with the exposure. The unexposed cohort consisted of remaining subjects without defined exposure, with cycles in the 6 weeks preceding the wildfires. As some subjects had dual exposure and appeared in both patient and laboratory exposure cohorts, each cohort was separately compared with the unexposed control cohort. INTERVENTION: A 10-day period of unhealthy air quality caused by smoke plumes from a wildfire event. MAIN OUTCOME MEASURES: The primary outcome was the blastulation rate. Secondary outcomes included fertilization rate, number of blastocysts obtained, and cycles with no blastocysts frozen or transferred. RESULTS: Sixty-nine subjects underwent ovarian stimulation and IVF treatment during the 6 weeks preceding the wildfires through the 10-day period of unhealthy air quality. Of these, 15 patients were in the laboratory exposure cohort, 16 were in the patient exposure cohort, and 44 were unexposed. Six subjects appeared in both laboratory and patient exposure cohorts. Although neither exposure cohort had significantly decreased blastulation rate compared with the unexposed, the median number of blastocysts obtained was significantly lower in the laboratory exposure cohort than the unexposed group (2 [range 0-14] vs. 4.5 [range 0-21], respectively). The laboratory exposure cohort had significantly more cycles with no blastocysts obtained (3/15 [20%] vs. 1/44 [2%]). There were no significant differences in IVF treatment outcomes between patient exposure and unexposed cohorts. These findings persisted after controlling for age. There were no significant differences in pregnancy outcomes observed after embryo transfer between the exposure group and the unexposed group. CONCLUSION: For a cohort of patients undergoing IVF treatment, an acute episode of outside wildfire smoke exposure during fertilization and embryogenesis was associated with decreased blastocyst yield.

Induction of somatic cell haploidy by premature cell division.

Canonical mitotic and meiotic cell divisions commence with replicated chromosomes consisting of two sister chromatids. Here, we developed and explored a model of premature cell division, where nonreplicated, G0/G1-stage somatic cell nuclei are transplanted to the metaphase cytoplasm of mouse oocytes. Subsequent cell division generates daughter cells with reduced ploidy. Unexpectedly, genome sequencing analysis revealed proper segregation of homologous chromosomes, resulting in complete haploid genomes. We observed a high occurrence of somatic genome haploidization in nuclei from inbred genetic backgrounds but not in hybrids, emphasizing the importance of sequence homology between homologs. These findings suggest that premature cell division relies on mechanisms similar to meiosis I, where genome haploidization is facilitated by homologous chromosome interactions, recognition, and pairing. Unlike meiosis, no evidence of recombination between somatic cell homologs was detected. Our study offers an alternative in vitro gametogenesis approach by directly reprogramming diploid somatic cells into haploid oocytes.

Desire for genetically related children among transgender and gender-diverse patients seeking gender-affirming hormones.

Objective: To assess predictors of desire for genetically related children among a national cohort of reproductive-age transgender and gender-diverse patients aged 18 to 44 years initiating gender-affirming hormone therapy for the first time. Design: Cross-sectional study. Setting: National telehealth clinic. Patients: A cohort of patients from 33 US states initiating gender-affirming hormone therapy. A total of 10,270 unique transgender and gender-diverse patients-aged 18 to 44 years (median age 24 years), with no prior use of gender-affirming hormone therapy-completed clinical intake forms between September 1, 2020, and January 1, 2022. Interventions: Patient sex assigned at birth, insurance status, age, and geographic location. Main Outcome Measures: Self-reported desire for children using own genetic material. Results: Transgender and gender-diverse patients seeking gender-affirming medical treatments who are open to having genetically related children are an important population to identify and appropriately counsel. Over one quarter of the study population reported being interested in or unsure about having genetically related children, with 17.8% reporting yes and 8.4% unsure. Male-sex-assigned-at-birth patients had 1.37 (95% confidence interval: 1.25, 1.41) times higher odds of being open to having genetically related children compared with female-sex-assigned-at-birth patients. Those with private insurance had 1.13 (95% confidence interval: 1.02, 1.37) times higher odds of being open to having genetically related children compared with those without insurance. Conclusions: These findings represent the largest source of self-reported data on the desire for genetically related children among reproductive-age adult transgender and gender-diverse patients seeking gender-affirming hormones. Guidelines recommend that providers offer fertility-related counseling. These results indicate that transgender and gender-diverse patients, particularly male-sex-assigned-at-birth individuals and patients with private insurance, could benefit from counseling regarding the impacts of gender-affirming hormone therapy and gender-affirming surgeries on fertility.

Strengthening the Reproductive Endocrinology and Infertility Curriculum Through Three Interactive Cases.

Introduction: Improved reproductive endocrinology and infertility (REI) curricula are needed to address educational deficiencies both at our institution and on a national level. To improve REI education for OB/GYN residents and medical students, we developed and piloted a curriculum with in-person and virtual flexibility. Methods: We developed three clinical vignettes for a facilitator-led case-based discussion among OB/GYN residents: two office cases and one emergency scenario. Cases were evaluated by content experts and tested before implementation. Pre- and postsurveys included both multiple-choice questions on content and a Likert-scale self-assessment of comfort, satisfaction, and knowledge. Postsurveys were administered immediately postintervention and at a delayed interval. Responses were compared using paired t tests and McNemar tests. Results: Eighteen learners (16 OB/GYN residents and two medical students) participated, the majority in person, of whom 17 (94%) completed a postsurvey. Self-rated proficiency in evaluating and managing irregular menses, infertility, and amenorrhea all improved significantly immediately following the intervention (p < .05 for all). Learners reported significantly more knowledge and comfort with REI compared to other subspecialties following the intervention (p < .05). More learners responded correctly to knowledge questions postintervention (p < .05 for questions 1 and 2, p = .16 for question 3). All learners were satisfied with and enjoyed the curriculum. Eight learners completed the delayed postsurvey and showed sustained improvements in knowledge and competence with REI content. Discussion: Facilitator-guided case-based learning was effective in improving learners' confidence, comfort, and knowledge in managing REI conditions, and improvements were sustained following a delayed interval.

Mifepristone-misoprostol combination treatment for early pregnancy loss after embryo transfer: a case series.

Objective: Evidence strongly supports the use of mifepristone-misoprostol combination treatment for early pregnancy loss (EPL) among pregnancies conceived without assisted reproductive technologies. No literature exists, however, regarding the efficacy of this treatment in the medical management of EPL among pregnancies after in vitro fertilization and embryo transfer (IVF-ET). These patients differ as some use exogenous hormonal supplementation to provide pregnancy support. Thus, the management for EPL may differ between unassisted conceptions and those after ET. Mifepristone, a progesterone receptor antagonist, may demonstrate an altered treatment effect when used with misoprostol to manage EPL in assisted reproductive technologie-conceived pregnancies. Objective: To describe our institution's experience using mifepristone-misoprostol to manage EPL after in vitro fertilization with embryo transfer IVF-ET. Design: Retrospective case series. Setting: Single academic institution from 2020 to 2022. Patientss: Nine patients with ultrasound confirmed EPL after IVF-ET. Interventions: All 9 patients underwent in vitro fertilization followed by fresh or frozen embryo transfer. All 9 received 200 mg of mifepristone 24 hours before 800 µg of misoprostol. Main Outcome Measurements: Incomplete abortion, need for surgical management, number of days to negative serum human chorionic gonadotropin (hCG). Results: Of the 9 subjects included, one had a programmed frozen embryo transfer cycle, 6 had modified natural frozen embryo transfer cycles, and 2 underwent fresh ET. Eight subjects had successful expulsion of tissue with one dose of treatment, and one required uterine aspiration. No subjects required additional dosing of misoprostol. The mean number of days elapsed from mifepristone treatment to tissue expulsion was 4.89 ± 11.30 days and the mean days to negative-range serum hCG was 36.89 ± 18.59 days. At the initial ultrasound, all pregnancies had one gestational sac seen; 5/9 had a yolk sac; only 3 had fetal cardiac activity. The mean gestational age at the time of EPL diagnosis was 55.22 ± 8.77 days, with the majority (8/9) having completed 7 weeks gestation. Conclusions: Mifepristone-misoprostol combination treatment appears to be a reasonable option for those with EPL after IVF-ET. Future, larger-scale studies are needed comparing combination treatment with misoprostol only among various ET protocols.

Reproductive endocrinologist and infertility specialists' knowledge, skills, behaviors, and attitudes regarding the care for transgender and gender-diverse individuals.

Objective: To investigate associations between reproductive endocrinology and infertility (REI) providers' prior training and current knowledge, skills, attitudes, and behaviors regarding fertility preservation and family building for transgender and gender-diverse (T/GD) patients. Design: The survey was distributed to members of the Society for Reproductive Endocrinology and Infertility, the REI-physician-focused professional body within the American Society for Reproductive Medicine, with additional participants recruited through snowball sampling. Results: Participants (n = 206) reported on training in T/GD care; 51% endorsed prior training. Most participants (93%) believed T/GD individuals were as fit for parenthood as cisgender individuals. Prior training was associated with an increased likelihood of offering T/GD health resources and more frequent consultations with specialist colleagues.Common barriers to providing care indicated by respondents included cost, delays in gender-affirming care, and lack of knowledge of the potential impact of hormonal interventions. Common facilitators included education and training, prior experience, and affordability of services. Conclusions: Most REI providers believed T/GD individuals are fit for parenthood and agreed that prior training facilitates care for T/GD patients. The lack of provider knowledge emerged as a barrier to care. Although training helped facilitate some components of care, systemic barriers such as the cost and variability of patient population characteristics/experiences are important considerations when serving T/GD individuals.

Limitations of gene editing assessments in human preimplantation embryos.

Range of DNA repair in response to double-strand breaks induced in human preimplantation embryos remains uncertain due to the complexity of analyzing single- or few-cell samples. Sequencing of such minute DNA input requires a whole genome amplification that can introduce artifacts, including coverage nonuniformity, amplification biases, and allelic dropouts at the target site. We show here that, on average, 26.6% of preexisting heterozygous loci in control single blastomere samples appear as homozygous after whole genome amplification indicative of allelic dropouts. To overcome these limitations, we validate on-target modifications seen in gene edited human embryos in embryonic stem cells. We show that, in addition to frequent indel mutations, biallelic double-strand breaks can also produce large deletions at the target site. Moreover, some embryonic stem cells show copy-neutral loss of heterozygosity at the cleavage site which is likely caused by interallelic gene conversion. However, the frequency of loss of heterozygosity in embryonic stem cells is lower than in blastomeres, suggesting that allelic dropouts is a common whole genome amplification outcome limiting genotyping accuracy in human preimplantation embryos.

Changing gender gap and practice patterns in reproductive endocrinology and infertility subspecialists in the United States: a Society for Reproductive Endocrinology and Infertility report.

OBJECTIVE: To identify changes in current practice patterns, salaries, and satisfaction by gender and by years in practice among board-certified reproductive endocrinology and infertility (REI) subspecialists in the United States. DESIGN: Cross-sectional web-based survey including 37 questions conducted by the Society for Reproductive Endocrinology and Infertility. SETTING: Not applicable. PATIENT(S): None. INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): The primary outcome measures were total compensation and practice patterns compared by gender and the type of practice. The secondary outcomes included demographics, the number of in vitro fertilization cycles, surgeries performed, and the morale of survey respondents. RESULT(S): There were 370 respondents (48.4% women and 51.4% men). Compared with a similar survey conducted 6 years earlier, a 27% increase in the number of female respondents was observed in this survey. There was a marginally significant trend toward lower compensation for female than male REI subspecialists (17% lower, $472,807 vs. $571,969). The gap was seen for responders with ≥10 years' experience, which is also when there was the largest gap between private and academic practice (mean $820,997 vs, $391,600). Most (77%) felt positively about the current state of the reproductive endocrinology field, and >90% would choose the subspecialty again. CONCLUSION(S): There has been a substantial increase in the number of recent female REI subspecialists showing less disparity in compensation, and the gap appears to be closing. There is an increasing gap in compensation between private and academic practices with ≥5 years of experience. Reproductive endocrinology and infertility remains a high morale specialty.