The effect of female body mass index on in vitro fertilization cycle outcomes: a multi-center analysis

The aim of this study is to examine the impact of female body mass index (BMI) on IVF cycle outcomes.

This is a retrospective cohort study including 51,198 women who initiated their first autologous IVF cycle in 13 fertility centers in the USA between 2009 and 2015. The effect of underweight, overweight, and obese BMI on four different IVF cycle outcomes (cycle cancellation, oocyte and embryo counts, and ongoing clinical pregnancy [OCP]) was evaluated in logistic or Poisson regression analyses with confounders adjusted.

Women with an overweight or obese BMI experienced worse outcomes than those with a normal BMI. These differences included (1) greater odds of cycle cancellation (aOR [95%CI] 1.17 [1.08, 1.26] for overweight, 1.28 [1.15, 1.41] for class-I obesity, and 1.50 [1.33, 1.68] for class-II/III obesity, P < .001 for all); (2) fewer oocytes retrieved (aIRR [95%CI] 0.98 [0.98,0.99] for class-I obesity, 0.93 [0.92,0.94] for class-II/III obesity, P < .001 for both); (3) fewer usable embryos (aIRR [95%CI] 0.98 [0.97,0.99] for overweight, 0.97 [0.96,0.99] for class-I obesity, 0.95 [0.93,0.97] for class-II/III obesity, P < .01 for all); and (4) lower odds of OCP (aOR [95%CI] 0.89 [0.83,0.95] for class-I obesity, 0.86 [0.79,0.93] for class-II/III obesity, P < .001 for both). In a subgroup analysis based on primary infertility diagnosis, these trends persisted in those with male or uterine factor and were especially pronounced in women with ovulatory dysfunction or PCOS.

A BMI above the normal range was an independent negative prognostic factor for multiple outcomes, including cycle cancellation, oocyte and embryo counts, and OCP. These negative outcomes were most profound in women with class-II/III obesity, ovulatory dysfunction, or PCOS.