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

Overview

The goal of this prospective observational cohort study is to evaluate whether body composition measured using bioelectrical impedance analysis (BIA) (including measures of body fat% and visceral fat) serve as a better predictor than body mass index (BMI) of outcomes of in vitro fertilization (IVF) cycles. Participants undergoing IVF will have body composition assessed using a BIA scale prior to treatment, including measurement of body fat percentage. Associations between BMI, BIA-derived body composition measures, and IVF treatment outcomes will be evaluated. Outcomes of interest include ovarian stimulation requirements, number of mature oocytes (eggs) retrieved, number of oocytes fertilized, and number and quality of embryos available for cryopreservation (freezing). Furthermore, ongoing pregnancy and miscarriage rates will be evaluated. The main question is to determine which of either BIA metrics or BMI are a better predictor of ongoing pregnancy or miscarriage rates. Furthermore, we would like to assess if there is an association between BIA metrics or BMI and the response to ovarian stimulation (egg recruitment), number and maturity rate of oocytes retrieved, number of oocytes fertilized and the number and quality of embryos available for cryopreservation. Participants will be asked to step on a BIA scale at the start of their cycle before taking medications to stimulate/recruit oocytes. This scale provides additional information on body fat % and visceral fat % in addition to body weight. The study aims to determine whether measures of adiposity obtained using BIA may provide a more informative assessment of the relationship between body composition and IVF outcomes than BMI alone.

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. BIA-derived measures, particularly body fat percentage, will be evaluated as continuous variables and compared with BMI with respect to their associations with IVF outcomes. Analyses will also consider relevant participant characteristics that may influence IVF outcomes, including age, ethnicity, smoking status, ovarian reserve testing, and other pre-specified demographic and clinical factors. The primary objective of the study is to determine whether BIA-derived measures of adiposity and body composition are associated with IVF treatment outcomes and whether these measures provide additional or improved predictive information compared with BMI alone. The study is observational. Participants will not be assigned to different treatment groups on the basis of BMI, body fat percentage, or other BIA measurements. All participants undergoing IVF who meet the inclusion criteria are invited to participate and will receive IVF treatment according to usual clinical practice. The study therefore evaluates naturally occurring variation in BMI and body composition as exposures of interest rather than testing an intervention. The findings from this study may help determine whether direct assessment of body composition provides clinically meaningful information beyond BMI when evaluating the relationship between adiposity and IVF outcomes. This information may inform future research examining the role of body composition in fertility treatment and potentially improve characterization of metabolic and reproductive risk among patients undergoing IVF.