RESUMO
OBJECTIVES: Smoking during pregnancy is a leading and modifiable risk factor for fetal growth restriction (FGR) and low birthweight (<10th centile). We studied the effects of smoking in the development of early and late FGR or low birthweight, as well as in uteroplacental and fetoplacental hemodynamics of growth-restricted fetuses. METHODS: Retrospective cohort study of 5,537 consecutive singleton pregnancies delivered at ≤34 + 0 ("early delivery" group, n=95) and >34 + 0 ("late delivery" group, n=5,442) weeks of gestation. Each group was divided into smokers and non-smokers. Prenatal diagnosis of FGR was based on customized fetal growth standards and fetal Doppler, and postnatal birthweight was assessed using the Olsen newborn chart. RESULTS: There were 15/95 (15.8%) and 602/5,442 (11.1%) smokers in the early and late delivery groups, respectively. In early deliveries, FGR was diagnosed in 3/15 (20%) of smokers and in 20/80 (25%) of non-smokers (p=0.68). We also found no differences in birthweights and hemodynamics. In late deliveres, FGR was detected in 30/602 (5%) smokers and 64/4,840 (1.3%) non-smokers (p<0.001). Birthweights <3rd centile and <10th centile were more common in smokers vs. non-smokers: 38/602 (6.3%) vs. 87/4,840 (1.8%) and 89/602 (14.8%) vs. 288/4,840 (6%), respectively (all p<0.01). Fetal Doppler of late FGR showed slightly higher umbilical artery resistances in smokers. CONCLUSIONS: Smoking in pregnancy is associated with FGR, low birthweight and higher umbilical artery Doppler resistances after 34 weeks of gestation, but we could not confirm this association in earlier deliveries.
