Maternal body mass index and periconception growth and development: a systematic review.

Complications of pregnancy are increasingly recognized 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 summarized comprehensively. This systematic review evaluates associations between maternal body mass index (BMI) and periconception outcomes, including oocyte quantity and maturity, preimplantation embryo quality, risk of miscarriage, 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 nine of 43 studies, and with fewer mature oocytes in eight of 30 studies. Negative associations with embryo quality were reported in 16 of 42 studies, including 13 at cleavage stage and three at blastocyst stage. Maternal BMI was associated with increased risk of miscarriage in 31 of 70 studies, and with altered embryonic growth in six of 11 studies. Overall, evidence across outcomes was heterogeneous. However, when significant associations were identified, they were in the direction of poorer periconception 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.