A prospective comparative study to assess the effect of maternal smoking at 37 weeks on Doppler flow velocity waveforms as well as foetal birth weight and placental weight.

Maternal smoking is known to have adverse effects on the foetus. This study aimed to evaluate the effects of maternal smoking during pregnancy on arterial blood flow velocities in the foetal-placental-maternal circulation, and the pathophysiological relationship with placental and foetal birth weight. A total of 148 singleton pregnancies in 59 smokers and 89 non-smoking controls were examined during the 37th week of gestation. Blood flow in the maternal uterine, foetal umbilical and middle cerebral arteries was analysed with Doppler ultrasonography. Statistically significant differences in Doppler waveforms were detected in the foetal umbilical artery (UmbA) (p < 0.05), but neither in uterine nor foetal middle cerebral arteries (p > 0.05). Both infant birthweight and placental weight were significantly decreased by maternal smoking (p< 0.001 for both). Maternal smoking during pregnancy did not affect either maternal uterine or foetal middle cerebral arterial blood flow, but caused abnormal blood flow in the foetal UmbA.