Overweight and obesity determined by body mass index criteria for Asian populations adversely affect assisted reproductive outcomes among Chinese women with polycystic ovary syndrome

Abstract

Background: Obesity is a common feature in women with polycystic ovary syndrome (PCOS) and is associated with multiple adverse reproductive outcomes. However, the impact of overweight and obesity on reproductive outcomes of women with PCOS who underwent in vitro fertilization-embryo transfer (IVF-ET) is currently controversial and appropriate body mass index (BMI) levels differ across ethnic groups.

Methods: This was a retrospective study including 1066 women with PCOS receiving IVF treatment at our institution between January 2018 and June 2021, among whom 960 underwent their first fresh or frozen embryo transfer. Participants were categorized according to BMI cut-off values proposed by the World Health Organization for Asian populations: normal weight (BMI < 23 kg/m²), overweight (BMI: 23-24.9 kg/m²), and obesity (BMI ≥ 25 kg/m²). The effect of BMI on clinical and embryological outcomes was evaluated by descriptive statistics and logistic regression models with confounders adjusted. The dose-response relationship between BMI as a continuous variable and IVF outcomes is also explored.

Interventions: no RESULTS: Increasing BMI was associated with significantly lower numbers of total oocytes retrieved, metaphase II oocytes, two pronuclear (2PN) zygotes, and good-quality embryos among women with PCOS. Patients with PCOS with a BMI ≥ 23 kg/m² had significantly lower live birth rates (41.9% vs. 49.1%; adjusted odds ratio [aOR], 0.75; 95% confidence interval [CI], 0.57-0.97) and implantation rates (35.8% vs. 43.9%; aOR, 0.76; 95% CI, 0.61-0.93) than those with normal BMI. Moreover, BMI showed a non-linear relationship (p for nonlinearity <0.001) with the number of 2PN zygotes with the curve becoming steeper as BMI surpassed 22.4 kg/m².

Conclusions: Patients with PCOS with a BMI ≥ 23 kg/m² have lower live birth rates than those with a BMI < 23 kg/m². Defining obesity and overweight with ethnicity-specific BMI cut-offs may help to improve IVF outcomes among PCOS patients.