Impact of low maternal weight on pregnancy and neonatal outcomes
Nikhita Chahal, Tanya Qureshi, Soukaina Eljamri, Janet M Catov, Pouneh K FazeliAbstract
Objective
To examine the effect of underweight maternal body mass index (BMI) on pregnancy complications and neonatal outcomes.
Design
Cohort study.
Setting
Tertiary academic center.
Patients
A total of 16,361 mothers who delivered a singleton between 2015-2021 with either a BMI <18.5kg/m2 (n=732) or normal BMI (18.5> BMI <23 or 25 kg/m2, n=15,629) at the initial prenatal visit or within six months of the initial visit.
Main Outcome Measures
Birthweight, gestational age, neonatal intensive care unit admission, preterm birth, and fetal death; obstetrical complications including pre-eclampsia/eclampsia, premature rupture of membranes, preterm premature rupture of membranes, and post-partum hemorrhage.
Results
Underweight women were younger and less likely to have private insurance (p<0.01 for both) than normal-weight women. Approximately 23% of infants born to underweight mothers were small for gestational age (SGA) and 15% were low birthweight versus 13.5% and 9% of infants of normal-weight mothers, respectively (p<0.01 for both). These differences remained significant after adjusting for potential confounders. In adjusted logistic regression models, underweight women had a decreased risk of premature rupture of membranes and post-partum hemorrhage compared to normal-weight women.
Conclusions
Underweight BMI during pregnancy is associated with an increased risk of small for gestational age and low birth weight infants and a decreased risk of premature rupture of membranes and post-partum hemorrhage. These findings suggest underweight BMI during pregnancy increases the risk of adverse neonatal outcomes, while maternal-related pregnancy outcomes are less affected.