SAN DIEGO – Smoking during the period of fetal organogenesis, during the first trimester of pregnancy, is associated with increased risk of some birth defects, results from a large retrospective analysis demonstrated.
Madeline Perry
Ms. Perry, a second-year medical student at the University of Cincinnati and her associates conducted a population-based retrospective cohort analysis of 1,436,036 live births in Ohio during 2006-2015. They compared the rates of major defects between births to nonsmoking mothers and those who smoked only during the 3-month preconception period and not in the first trimester; and in the preconception period plus throughout the first trimester. They used multivariate logistic regression to quantify the relationship between smoking and birth defects after adjustment for maternal race, age, pregestational diabetes, and socioeconomic factors.
The researchers observed that 23.3% of women smoked during pregnancy; 6.0% during preconception only and 17.3% smoked through the first trimester, as well. Smoking during the preconception period only, even without first trimester exposure, was associated with a 40% increased risk of gastroschisis (adjusted risk ratio, 1.4), but no other individual birth defects. However, smoking through the first trimester was associated with a modest but significantly increased risk of several defects, including gastroschisis (adjusted RR, 1.9), limb reduction (adjusted RR, 1.6), congenital diaphragmatic hernia (adjusted RR, 1.4), and cleft palate (adjusted RR, 1.2), even after adjustment for coexisting factors.
“It was surprising to see that, even when women stop smoking when they find out they are pregnant, and therefore are not smoking during the period of fetal organogenesis, there is still an increased risk of some congenital birth defects to the fetus,” Ms. Perry said. “My hope is that this study serves as a launching point for future research and public health efforts. It’s important to encourage smoking cessation in women of reproductive age, whether pregnant or not. Furthermore, it’s valuable to be able to explain to patients that along with adverse effects to their own health, smoking even before conception poses a risk to the fetus.”
She acknowledged certain limitations of the study, including its observational design. “There could exist unmeasurable influences that we were unable to adjust for,” Ms. Perry said. She reported having no financial disclosures.