LATEBREAKER
Reproductive
Joint Effect of Maternal Smoking Patterns during Pregnancy and Pre-Pregnancy BMI on Infant Birth Outcomes Rachel E. Wacks* Rachel Wacks Christian P. Daniele Cassandra N. Spracklen
Background: The independent relationships between smoking during pregnancy or pre-pregnancy BMI (ppBMI) and increased risks for adverse maternal and fetal pregnancy outcomes are well understood. However, little is known about the potential interaction between patterns of smoking during pregnancy and ppBMI. As such, we aimed to evaluate the combined association between smoking patterns during pregnancy and ppBMI with risks for delivering an infant born small for gestational age (weight <10th % for gestational age; SGA), low or high birthweight (<2500g or >4000g; LBW or HBW), or preterm (<37 weeks; PTB).
Methods: Within the Iowa Health in Pregnancy Study (IHIPS), a population-based case-control study of PTB and SGA infants, 2,308 women completed a computer-assisted telephone interview in which they reported smoking during pregnancy (ever/never) during the index pregnancy. ppBMI and infant outcomes were obtained from prenatal and hospital delivery records. Multivariable logistic regression analyses were performed to assess the associations and potential interactions between ppBMI and smoking patterns during pregnancy on infant outcomes.
Results: Of 2,308 included IHIPS participants, there were 504 SGA (25.71%), 806 PTB (29.3%), 330 LBW (12.0%), and 121 HBW (4.4%) infants. Smoking during pregnancy was independently associated with LBW (OR: 1.79; 95% CI 1.45-2.09), SGA (OR: 1.57; 95% CI 1.22-2.01), and HBW (OR: 0.49; 95% CI 0.28-0.85). Having a ppBMI ≥30 was independently associated with PTB (OR: 1.45; 95% CI 1.16-1.81) and LBW (OR: 1.24; 95% CI 1.01-1.53), while having a ppBMI of 25.0-29.9 was a statistically significant predictor for HBW (OR: 1.78; 95% CI 1.16-2.71) and SGA (OR: 0.73; 95% CI 0.56-0.96).
Conclusions: We did not detect effect modification between smoking during pregnancy and ppBMI.