Beyond body mass index: A contemporary review of obesity and female infertility.

Obesity is increasingly understood as a reproductive-metabolic condition that can affect female fertility across the continuum from natural conception to assisted reproductive technology (ART). Excess adiposity may disrupt hypothalamic-pituitary-ovarian regulation, insulin signaling, inflammatory pathways, ovarian function, oocyte competence, embryo development, and endometrial receptivity. This review synthesizes current evidence linking obesity with infertility, reduced ART efficiency, implantation failure, miscarriage, and reduced live birth, while emphasizing that these associations vary according to reproductive and metabolic phenotype. Particular attention is given to polycystic ovary syndrome, advanced age, diminished ovarian reserve, recurrent implantation failure, and recurrent pregnancy loss. Pre-treatment weight-loss strategies, including lifestyle intervention, glucagon-like peptide-1 receptor agonists, tirzepatide, and bariatric surgery, are also considered in relation to reproductive benefit, treatment delay, and pregnancy safety. Overall, obesity should not be treated simply as a body mass index category, but rather as a phenotype-dependent reproductive-metabolic condition that requires individualized fertility-treatment planning.