To assess whether coronavirus disease 2019 (COVID-19) mRNA vaccination is associated with controlled ovarian hyperstimulation or early pregnancy outcomes. METHODS:This retrospective cohort study included patients who underwent controlled ovarian hyperstimulation or single euploid frozen-thawed embryo transfer at a single academic center. Patients fully vaccinated with a COVID-19 mRNA vaccine were compared with unvaccinated patients who cycled during the same time period. The primary outcome was the fertilization rate for controlled ovarian hyperstimulation and the clinical pregnancy rate for frozen-thawed embryo transfer. Secondary outcomes for controlled ovarian hyperstimulation included eggs retrieved, mature oocytes retrieved, mature oocytes ratio, blastulation rate, and euploid rate. Secondary outcomes for frozen-thawed embryo transfer included preg-nancy rate, ongoing pregnancy rate, biochemical pregnancy loss rate, and clinical pregnancy loss rate.See related editorial on page 479.

Objective To evaluate the relation of endometrial thickness (EnT) and endometrial pattern (EnP) to euploid embryo transfer (ET) outcomes. Design Retrospective cohort Setting Private academic clinic Patients Patients (n=277, 36.1±4.0 years) whose embryos (n=476) underwent aneuploidy screening with fresh (n=176) or frozen (n=180) ET from July 2010–March 2014. Interventions EnT and EnP were measured on trigger day and at ET. Patients were stratified by age and cycle type (fresh or frozen). Cycle data were combined at trigger day but separated at ET day. Main Outcome Measures Outcome measures were implantation (IR), pregnancy (PR) and clinical pregnancy (CPR) rates. Analysis was conducted by chi-square and Fisher exact test with significance at p<0.05. Results 234 gestational sacs, 251 pregnancies and 202 clinical pregnancies resulted from 356 cycles. EnT (9.6±1.8mm; range 5–15mm) at trigger day (n=241 cycles) as a continuous or categorical (≤8 vs >8mm) variable was not associated with IR, PR or CPR. EnT at day of fresh (9.7±2.2mm; range 4.4–17.9mm) (n=176 cycles) or frozen ET (9.1±2.1mm; range 4.2–17.7mm) (n=180 cycles) was not associated with IR, PR or CPR. Type 3 EnP at trigger day was associated with increased serum progesterone at trigger and decreased IR compared with type 2 EnP. EnP at fresh or frozen ET was not associated with IR, PR or CPR. Conclusions Within the study population, EnT was not significantly associated with clinical outcomes of euploid ETs. A type 3 EnP at trigger day suggests a prematurely closed window of implantation.

A BMI above the normal range was an independent negative prognostic factor for multiple outcomes, including cycle cancellation, oocyte and embryo counts, and OCP. These negative outcomes were most profound in women with class-II/III obesity, ovulatory dysfunction, or PCOS.