Body mass index: impact on IVF success appears age-related.

BACKGROUND

The objective of this study was to examine the effect of BMI on IVF outcomes.

METHODS

This was a retrospective analysis of all patients undergoing IVF from 1st January 2005 to 1st March 2006 in a large private practice using a single IVF laboratory. The patients underwent standard protocols for controlled ovarian hyperstimulation and embryology parameters. The main outcome measure was clinical pregnancy rate.

RESULTS

A total of 2167 fresh, non-donor IVF cycles were queried, but to minimize bias, only the first treatment cycle for each patient was analyzed (n = 1273). The data were examined by multiple regression models that included BMI and Age as main effects plus a BMI x Age interaction. When examined as a main effect, BMI did not appear to have a major effect on IVF outcome, but there was a significant BMI x Age interaction. At younger ages, a high BMI had a pronounced negative influence on fertility, but this effect diminished as the patient age increased. Clinical pregnancy rates decreased with increasing BMI and increasing Age.

CONCLUSIONS

In younger patients undergoing IVF, BMI has a significant negative impact on fertility that diminishes as patients reach their mid thirties. After Age 36, BMI has a minimal impact on fertility.