Reproductive Outcomes and Maternal Weight

Reproductive outcomes have been shown to be linked to maternal weight in a wide variety of studies. Underweight and overweight may affect reproduction and interfere with treatment of infertility. In the present retrospective analysis, Zheng, J., Cai, J., Liu, L. et al. sought to evaluate the effect of low body mass index (BMI) on pregnancy and perinatal outcomes in frozen–thawed embryo transfer (FET) cycles.

There is, however, very little data with respect to how being underweight (body mass index [BMI] < 18.5 kg/m²) influences these same outcomes. Studies that have been published provide inconsistent findings, potentially as a consequence of variability in methodology, inclusion criteria, BMI definitions, outcomes assessed, or adjustments based on confounding variables.

To evaluate the association between body mass index (BMI) and pregnancy outcomes in women receiving intrauterine insemination (IUI) treatment, the study included 6407 women undergoing 13,745 IUI cycles stratified by BMI. Cox regression was used to analyze the association between BMI and cumulative live births across multiple IUI cycles. A generalized estimating equation (GEE) was used to analyze the live birth rate per cycle.

Compared with normal-weight women (n = 4563), underweight women (n = 990) had a lower cumulative pregnancy and live birth rate (20.71% vs 25.93% and 17.17% vs 21.61%, respectively), while overweight women (n = 854) had a higher cumulative pregnancy and live birth rate (31.97%, 26.58%). Adjusted for confounders, the hazard ratio (HR) for achieving live birth following up to a maximum of four IUI cycles was 0.80 (95% CI: 0.67–0.95), comparing underweight with normal weight. In the GEE analyses, low BMI was also associated with a lower per-cycle birth rate (OR 0.79, 95% CI: 0.66–0.95), with adjustment for cycle-specific parameters, including ovarian stimulation, endometrial thickness, and follicular diameter.

The authors concluded that low BMI is associated with poor IUI outcomes.

Source: Zheng, J., Cai, J., Liu, L. et al. Low BMI is associated with poor IUI outcomes: a retrospective study in 13,745 cycles. J Assist Reprod Genet (2022). https://doi.org/10.1007/s10815-022-02658-y