BMI Versus Body Fat Percentage - Which is the Better Predictor of Fertility Outcomes in IVF Cycles?

Obesity and increased adiposity have been associated with differences in ovarian response to controlled ovarian stimulation and with reproductive outcomes following in vitro fertilization (IVF) in certain studies with a notable degree of heterogeneity. Body mass index (BMI) is an anthropometric commonly used to estimate adiposity. In reproductive medicine and elsewhere, BMI is used to guide clinical risk assessment, dose gonadotropins for ovarian stimulation, and prognosticate IVF outcomes. With that said, BMI does not distinguish between fat mass and lean body mass and may therefore provide an incomplete assessment of adiposity and body composition.

Bioelectrical impedance analysis (BIA) is a non-invasive method of estimating body composition, including body fat percentage, fat mass, and lean body mass. This prospective observational cohort study will evaluate whether body composition measurements obtained using a BIA scale are associated with ovarian stimulation parameters, embryologic outcomes, and early pregnancy outcomes among patients undergoing IVF. Ultimately, we would like to ascertain which of BMI or BIA are better predictors of IVF success.

Participants will be recruited at the time of planning an IVF treatment cycle. Following informed consent, participants will undergo a standardized BIA measurement prior to or at the beginning of their IVF treatment cycle. Height and weight will also be recorded and used to calculate BMI. The BIA assessment is performed for research purposes and will not be used to determine eligibility for IVF treatment, select the ovarian stimulation protocol, modify medication doses, or otherwise alter the participant's clinical care.

Participants will subsequently undergo IVF treatment according to standard clinical practice. Clinical and laboratory information generated during routine IVF care will be collected from the participant's medical record. Data collected will include demographic and baseline clinical characteristics, ovarian stimulation parameters, embryologic outcomes, and pregnancy outcomes.

The study will examine relationships between BMI and BIA-derived measures of body composition and IVF outcomes. Outcomes of interest will include measures of ovarian response, such as total gonadotropin requirement and number of oocytes retrieved; embryologic outcomes, including mature oocyte yield and number and quality of embryos available for cryopreservation; and reproductive outcomes, including biochemical pregnancy, clinical pregnancy, ongoing pregnancy, and early pregnancy loss, where applicable.