Female obesity increases the risk of miscarriage of euploid embryos

To determine whether female body mass index (BMI) is associated with an increased risk of miscarriage after euploid embryo transfer.

A retrospective, observational, multicenter cohort study.

University-affiliated in vitro fertilization center.

In this study, 3,480 cycles of in vitro fertilization with preimplantation genetic testing for aneuploidy (PGT-A) in the blastocyst stage and euploid embryo transfer were divided into four groups according to patient BMI.

In vitro fertilization with PGT-A.

The primary outcome was the miscarriage rate, which included both biochemical and clinical miscarriages. Secondary outcomes were implantation, pregnancy, clinical pregnancy, and live birth rates.

Cycles were divided into four groups according to BMI (kg/m²): underweight (<18.5; n = 155), normal weight (18.5-24.9; n = 2,549), overweight (25-29.9; n = 591), and obese (≥30; n = 185). The number of PGT-A cycles per patient was similar in the four groups. Fertilization rate, day of embryo biopsy, technique of chromosomal analysis, number of euploid embryos, number of transferred embryos, and method of endometrial preparation for embryo transfer were similar in the four BMI groups. Miscarriage rates were significantly higher in women with obesity compared to women with normal weight, mainly due to a significant increase in the clinical miscarriage rates. Live birth rates also were lower in women with obesity. Obesity in women and day 6 trophectoderm biopsy were found to influence the reduced live birth rate.

Women with obesity experience a higher rate of miscarriage after euploid embryo transfer than women with a normal weight, suggesting that other mechanisms than aneuploidy are responsible for this outcome.