A relationship between progesterone, maternal body weight, and offspring sex following the frozen/thawed single embryo transfer.

Abstract

Abstract Background/Objectives: to investigate a possible relationship between women’s age, serum progesterone concentration (PRG), and body weight expressed by body mass index (BMI) on the day of embryo frozen/thawed transfer (FET), and the sex of the newborn baby. Subjects/Methods: A retrospective cohort study concerning children born after FET cycles conducted in one fertility clinic between January 2018 and September 2022. Out of 2,502 FET cycles, a group of 928 patients who underwent the transfer of the first best embryo from all frozen embryos, was extracted. All patients aged 23–46 qualified for FET during the study period were considered eligible. Cases where two embryos were transferred, and cycles where no data on progesterone concentration or embryos frozen at the cleavage stage were excluded from the study. Results: Odds ratio (OR) of maternal age (OR: 0.97; 95% CI: 0.94–1.00; p = 0.064), PRG (OR: 1.00; 95% CI: 0.77–1.30; p = 0.988), and BMI (OR: 1.01; 95% CI: 0.98–1.05; p = 0.478) were not found to be associated with childbirth. Moreover, the maternal age did not have a statistically significant effect on the likelihood of giving birth to a female child (OR: 0.99, 95% CI: 0.95–1.02; p = 0.495) or a male child (OR: 0.97, 95% CI: 0.94–1.01; p = 0.128). However, the study found that increased levels of PRG over 20 ng/ml (OR: 1.38, 95% CI: 1.01–1.89; p = 0.044) and increased maternal BMI (OR: 1.06, 95% CI: 1.01–1.10; p = 0.007) significantly raised the chance of giving birth to a girl. Conversely, PRG levels less than 20 ng/ml are associated with lower odds of male birth (OR: 0.72, 95% CI: 0.53–0.99; p = 0.044), and higher maternal BMI is associated with an almost statistically-significant lower chance of male birth (OR = 0.96, 95% CI: 0.92–1.00; p = 0.067). Conclusion: Higher BMI and PRG levels positively predicted female childbirth; conversely, elevated levels negatively predicted male delivery.