This study aimed to explore the effects of body mass index on the pregnancy outcomes in different age groups in women undergoing their first frozen-thawed embryo transfer cycle. A total of 1006 patients undergoing their first single high-quality blastocyst FET between January 2019 and January 2023 at the Center of Reproductive Medicine, the Fourth Hospital of Shijiazhuang, were considered in this retrospective cohort study. First, the included patients were classified into three groups according to their BMI: underweight (BMI 0.05). Age-stratified analysis with Bonferroni correction showed that among women aged 0.05). However, within the 30–34 years age group, the miscarriage rate in the overweight/obese group was significantly higher than that in the normal weight group, with a statistically significant difference (P = 0.005). No significant Age × BMI interaction was observed (all P > 0.05). Multivariate binary logistic regression analysis showed that advanced age was an independent risk factor for both clinical pregnancy and live birth rate in frozen-thawed embryo transfer (FET) cycles, whereas higher BMI was an independent risk factor for miscarriage. Although the BMI can greatly affect the miscarriage rate of women aged 30–34 years, it has almost no effects on the outcomes of younger or older women. Advanced age and higher BMI are independent risk factors for adverse outcomes.
Zhang et al. (Fri,) studied this question.