Periconceptional maternal body mass index and the impact on post-implantation (sex-specific) embryonic growth and morphological development

Abstract

Objective: Women with obesity have an increased risk of pregnancy complications. Although complications generally present in the second and third trimester of pregnancy, most of them develop in the periconception period. Moreover, fetal sex also impacts pregnancy course and outcome. Therefore, our aim is to study (sex-specific) associations between periconceptional maternal body mass index (BMI) and embryonic growth and morphological development.

Methods: A total of 884 women with singleton pregnancies were selected from the Rotterdam Periconception Cohort, comprising 15 women with underweight, 483 with normal weight, 231 with overweight and 155 with obesity. Longitudinal three-dimensional ultrasound examinations were performed at 7, 9, and 11 weeks of gestation for offline measurements of crown-rump length (CRL), embryonic volume (EV), and Carnegie stages. Analyses were adjusted for maternal age, parity, ethnicity, education, and periconceptional lifestyle.

Results: A negative trend was observed for embryos of women with obesity (β_EV -0.03, p = 0.086), whereas embryonic growth and developmental trajectories in women with overweight were comparable to those with normal weight. Maternal underweight was associated with faster morphological development (β_Carnegie 0.78, p = 0.004). After stratification for fetal sex, it was demonstrated that female embryos of underweight women grow and morphologically develop faster than those of normal weight women (β_EV 0.13, p = 0.008; β_Carnegie 1.39, p < 0.001), whereas female embryos of women with obesity grow slower (β_EV -0.05, p = 0.027).

Conclusion: We found that periconceptional maternal underweight is associated with faster embryonic growth, especially in females. In contrast, female embryos of women with obesity grow slower than female embryos of women with normal weight. This may be the result of altered female adaptation to the postnatal environment. Future research should focus on strategies for optimizing preconceptional maternal weight, to reduce BMI-related pregnancy complications and improve the health of future generations.