Aim: While there are sufficient data regarding the negative effect of exposure to the constituents of tobacco smoke on newborn infants' birth weights, it is still unclear whether this effect may originate in early pregnancy. The aim of the present study was to evaluate the impact of exposure to tobacco smoke components in early pregnancy (20-24 weeks) on fetal biometry.
Methods: The study population comprised 183 women consecutively enrolled at 20-24 weeks of pregnancy at the two antenatal care units. Ultrasound biometric measurements of fetal bi-parietal diameter (BPD), abdominal circumference (AC) and femur length (FL) were performed at the time of enrollment. Serum cotinine concentration was determined at 20-24 weeks of gestation by gas chromatography with mass spectrometry detector (GC/MS) to assess environmental tobacco smoke (ETS) exposure during the previous evening and the morning of the same day (blood collection at 1200-1300 h). ETS exposure (passive smoking) was assumed to occur when the level of serum cotinine ranged from 2-10 ng/ml.
Results: In a multiple regression model for bi-parietal diameter (BPD), after adjustment for pregnancy duration at the time of ultrasound examination, fetal gender, and maternal pre-pregnancy weight, a statistically significant negative association was found between the BPD and serum cotinine concentration. A similar association was identified for subjects with serum cotinine concentrations below 10 ng/ml (corresponding to passive smoking) (P=0.06). After controlling for pregnancy duration, maternal pre-pregnancy weight and infant's gender, we found that serum cotinine levels at 20-24 weeks of gestation was inversely associated with infant birth weight (P=0.004). For the subjects with serum cotinine levels below 10 ng/ml, a borderline association (P=0.09) with infant birth weight was found.
Conclusions: Maternal exposure to tobacco smoke in early pregnancy, as measured by serum cotinine concentrations at 20-24 weeks of gestation, adversely affects fetal BPD. Preventive measures need to be undertaken to encourage pregnant women to stop smoking and avoid passive exposure to tobacco smoke from the very beginning of pregnancy.