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.