Objective: To evaluate the impact of body mass index associated with advanced maternal age on pregnancy outcomes.
Methods: 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.
Results: 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.
Conclusions: 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.
Keywords: body mass index; embryo transfer; in vitro fertilization; maternal age; pregnancy rate.