Impact of in utero tobacco exposure on fetal growth: Amount of exposure and second trimester fetal growth measurements.

Background: Research reveals small and inconsistent findings linking prenatal tobacco exposure and early fetal growth, but failure to consider confounding and amount of exposure many explain inconsistencies.

Goal: To examine whether fetal growth effects following exposure to tobacco are evident in the second trimester, specific to certain growth parameters, and dose dependent.

Methods: Participants were pregnant women (64 smokers, 100 controls) with no other drug use. Available data included background/medical information and ultrasound measurements coded as percentiles.

Results: Controlling for background differences, 10+ cig/day predicted a 10+ percentile point reduction in estimated fetal weight, femur length, head circumference, and biparietal diameter compared to non-exposed controls. Exposure to <10 cig/day predicted significant reduction in only biparietal diameter. Exposure was unrelated to abdominal circumference.

Conclusions: Results demonstrate utility of considering amount of exposure when examining/quantifying fetal growth effects, and suggest even reduction in early pregnancy smoking may positively benefit aspects of fetal development.