Effect of maternal body mass index on neonatal outcomes in women with endometriosis undergoing IVF

Does preconception body mass index (BMI) affect neonatal outcomes in women with endometriosis who conceive with IVF?

This retrospective study included 7086 women who delivered a singleton live birth through IVF between December 2006 and December 2017. Of these, 1111 women were diagnosed with endometriosis by laparoscopy or laparotomy, while 5975 women received IVF treatment due to tubal factor or male factor infertility. Women were categorized according to predefined BMI groups (<18.5 kg/m², BMI 18.5-24.9 kg/m², ≥25 kg/m²). All comparisons performed were between women undergoing cryopreserved embryo transfer.

After stratification by BMI, underweight women with endometriosis showed higher preterm birth (PTB) rates compared with controls (14.61% versus 3.28%, P < 0.001), whereas normal weight and overweight/obese endometriotic women had similar PTB rates to controls. There was a significant interactive effect of endometriosis and maternal BMI on preterm delivery (P for interaction <0.05). After adjustment for potential confounding factors, the PTB rate remained consistently higher in the low BMI subgroup of women with endometriosis (adjusted odds ratio 4.66, 95% confidence interval 2.54-8.57), whereas this difference was not observed for the other BMI categories. Additionally, we noted no differences in the rate of early PTB, low birthweight, macrosomia, small for gestational age and large for gestational age between women with endometriosis and controls with respect to any preconception category of BMI.

Endometriotic patients who were underweight before conception (BMI <18.5 kg/m²) had a higher rate of PTB than women without endometriosis, but the difference was not observed in the other BMI categories.