Study question: When adjusting for recipient BMI, is donor body mass index (BMI) associated with IVF outcomes in donor oocyte IVF cycles?

Summary answer: Increasing oocyte donor BMI is associated with a reduction in clinical pregnancy and live birth rates.

What is known already: Increased BMI has been associated with suboptimal reproductive outcomes, particularly in assisted reproductive technology (ART) cycles. However, it remains unclear if this association implies an effect of BMI on oocyte quality and/or endometrial receptivity.

Study design, size, duration: A retrospective cohort study of two hundred and thirty five consecutive fresh donor oocyte IVF cycles from 1 January 2007 through 31 December 2013 at the Massachusetts General Hospital (MGH) Fertility Center.

Participants/materials, setting, methods: Analyses included a total of 202 oocyte donors and 235 total cycles. Following adjustments for recipient BMI, the relationship between donor BMI (categorized into quartiles) and IVF outcomes was assessed.

Main results and the role of chance: In the entire (anonymous and known) donor population, a reduced odds of clinical pregnancy (P-trend = 0.046) and live birth (P-trend = 0.06) was observed with increasing BMI quartile. Compared with quartile 1 (BMI 17.8-21.1), odds ratio (OR) (95% CI) of clinical pregnancy was 0.9 (0.4-2.0), 0.5 (0.2-1.1) and 0.5 (0.2-1.1), and OR of live birth was 1.1 (0.5-2.6), 0.6 (0.3-1.2) and 0.6 (0.3-1.2) for quartiles 2 through 4 respectively. In anonymous donors only, the odds of clinical pregnancy (P-trend = 0.02) and live birth (P-trend = 0.03) also declined as BMI quartile increased. Compared with quartile 1 (BMI 17.8-21.1), odds ratio (OR) (95% CI) of clinical pregnancy was 0.7 (0.3-1.7), 0.5 (0.2-1.1) and 0.4 (0.1-0.9), and OR of live birth was 0.9 (0.4-2.2), 0.5 (0.3-1.2) and 0.4 (0.2-1.1) for quartiles 2 through 4 respectively.

Limitations, reasons for caution: Limitations include the retrospective design, sample size and data from a single institution. Clinical application may not be limited to oocyte donors, though caution should be used prior to applying these principles to the general population. Data should not be interpreted to mean that all oocyte donors should be restricted to a BMI of less than 21.2 kg/m(2).

Wider implications of the findings: Following adjustments for the respective BMI of the oocyte donor and recipient, this study demonstrates an association of preconception BMI with subsequent IVF outcomes. The observations of this study are consistent with prior animal studies, suggest a possible effect of BMI at the oocyte level prior to fertilization and implantation, and warrant further investigation.

Study funding/competing interests: None.