Impact of Body Mass Index and advanced maternal age on in vitro fertilization outcomes

To evaluate the impact of body mass index associated with advanced maternal age on pregnancy outcomes.

A retrospective and observational study that included 808 in vitro fertilization cycles and evaluated: age, weight, height, number of oocytes and mature oocytes, number of embryos and transferred embryos, fertilization and clinical pregnancy rates. Four categories of body mass index: underweight, adequate weight, overweight and obesity. We classified age into 4 categories: 35-37; 38-40; 41-42 and over 42 years of age. The means and rates were calculated and compared between different ages and body mass index groups.

For the fresh group, women who achieved clinical pregnancy had a lower mean age than those who did not become pregnant, being the higher the pregnancy rate the lower the age (p<0.0001). After logistic regression analysis for data associated with clinical pregnancy in the fresh group, the number of transferred embryos remained higher in the overweight category (p=0.0001). Overweight and obese women had a significantly higher rate of mature oocytes when compared with adequate weight (p=0.015). Analysis using the ROC curve indicated an area under the curve of 60% (p=0.002) for the fresh group.

The adverse effect of high BMI on clinical pregnancy rates is greater in women under 35 years compared to older women; and age had a higher impact on live birth rate rather than BMI, when the analysis was performed on older women, with the impact of BMI on the probability of having a live birth depending on maternal age.