A propensity-matched study of the association between prepregnancy maternal underweight and perinatal outcomes among singletons based on an ART cohort

Research question

Is prepregnancy maternal underweight associated with perinatal outcomes of singletons who were conceived by assisted reproductive technology (ART)?

A 10-year (2006-2015) Chinese sample of 6538 women and their singletons who were conceived by ART was used to examine the association between prepregnancy maternal underweight and perinatal outcomes. Propensity scores(PS) for underweight were calculated for each participant using multivariable logistic regression, which was used to match 740 (91.35% of 810) underweight women with 740 normal weight women and then the effects of underweight on birth weight (BW) and gestational age (GA) were assessed by the generalized estimating equation (GEE) model.

Results

After PS matching, the BW was lower (difference=-136.83 g, 95% CI=-184.11 to -89.55 g) in the underweight group than in the normal weight group. The risks of low birth weight (LBW) and small for gestational age (SGA) were increased in the underweight group compared with those in the normal weight group (LBW: RR=1.64, 95% CI=1.01 to 2.67; SGA: RR=1.46, 95% CI=1.06 to 2.02). The risks of fetal macrosomia and being large for gestational age (LGA) were decreased in the underweight group compared with those in the normal weight group (macrosomia: RR=0.39, 95% CI=0.26 to 0.61; LGA: RR=0.36, 95% CI=0.24 to 0.53). The associations between underweight and GA and preterm birth (PTB) were not statistically significant.

Conclusions

Among women undergoing ART, prepregnancy maternal underweight was associated with lower BW, increased LBW and SGA risks and decreased fetal macrosomia and LGA risks in singletons.