Abstract
Objective Small-for-gestational age infants are at an increased risk for disabilities and chronic
health problems. Smoking and hypertension during pregnancy pose significant risks
for fetal growth restriction. The study aims to identify whether (1) the timing of
tobacco use modifies the risk of small-for-gestational age, (2) there are differences
in association by percentile of small-for-gestational age (3rd, 5th, and 10th percentile),
and (3) the effect of tobacco exposure on small-for-gestational age outcome is mediated
by hypertension.
Materials and Methods Data were obtained from the 2009 Natality public use file available through the National
Center for Health Statistics. Women were categorized into 11 groups depending on the
trimester of tobacco exposure, the number of daily cigarettes smoked, and presence
of hypertension. Multivariable log-linear regression models were performed to determine
the association between percentile of singleton small-for-gestational age outcome
(3rd, 5th, and 10th), trimester and degree of tobacco exposure, and hypertension.
Results Hypertension and smoking worked synergistically to restrict fetal growth. Hypertensive
women who smoked heavily in all three trimesters were 4.34 times more likely to give
birth to a 3rd percentile small-for-gestational age infant compared with nonsmoking
normotensive women.
Conclusion The timing and duration of tobacco exposure mediates the risk and severity of fetal
growth restriction.
Keywords
hypertension - small-for-gestational age - tobacco - trimester of pregnancy
