The most comprehensive study to date regarding the impact of female obesity on IVF outcomes is from the Society for Assisted Reproductive Technology (SART) registry (Provost MP, et al., 2016). This analysis involved 239127 fresh IVF cycles from 2008 to 2010 and included over 6000 cycles in women with a BMI 30 to 40 and almost 1000 cycles in women with a BMI over 40. Cycles in patients with a normal BMI (18.5–24.9 kg/m2 ) were used as the reference group. The results of this study are summarized in Table 2.
In brief, there is a slight decline in the number of oocytes retrieved and the number of high-quality embryos as the BMI rises over 40. Implantation, clinical pregnancy, and live birth rates all decline gradually with increasing severity of obesity.
The association between BMI and the number of embryos showed a quadratic relationship with an inverse U-formed curve with fewer embryos among the low-weight and the obese women. Thus both low BMI and obesity were negative predictors of the number of developed embryos in the first IVF or ICSI cycle, with BMI approximately 22 kg/m 2 as the most optimal for ovarian response (Pinborg A, et al. 2011)
Women with obesity have a reduced response to fertility medications, reduced likelihood of success with assisted reproductive technologies, increased risk of miscarriage and increased risk of maternal/fetal complications in pregnancy. Weight loss is the mainstay of treatment and is important for optimizing the safety and success of natural and treatment-related conception. Therefore, educational interventions based on the adverse effects of obesity and the benefits of weight reduction in increasing pregnancy rates among couples suffering from infertility are needed.