Maternal body mass index and periconception growth and development: A systematic review

Complications of pregnancy are increasingly recognised to originate in the periconception period when the foundation for successful implantation and early development is established. Maternal obesity is increasingly prevalent and associated with adverse reproductive outcomes, but its specific impact during this critical window has not been comprehensively summarised. This systematic review evaluates associations between maternal body mass index (BMI) and periconception outcomes, including oocyte quantity and maturity, preimplantation embryo quality, miscarriage risk and embryonic growth. A systematic search of Embase, Medline, PubMed, Web of Science, Cochrane, and Google Scholar identified 101 studies from 20,868 screened records published up to January 2025. High maternal BMI was associated with reduced oocyte numbers in 9 of 43 studies and fewer mature oocytes in 8 of 30 studies. Negative associations with embryo quality were reported in 16 of 42 studies, including 13 at cleavage and 3 at blastocyst stage. Maternal BMI was associated with increased miscarriage risk in 31 of 70 studies and altered embryonic growth in 6 of 11 studies. Overall, evidence across outcomes was heterogeneous. However, when significant associations were identified, they were in the direction of poorer periconceptional outcomes with increasing BMI. Given the rising prevalence of obesity, future research should focus on causal pathways, early recognition of complications and developing preventative strategies.