The influence of smoking during pregnancy on fetal growth. Considering daily cigarette consumption and the SGA rate according to length of gestation.

ABSTRACT

BACKGROUND: Smoking is the most important risk factor for adverse pregnancy outcomes in industrialized nations and is associated with, amongst other adverse effects, a higher rate of small-for-gestational-age (SGA) neonates. The rate of SGA neonates born before 32 weeks and its association with smoking have so far not been the focus of attention. MATERIAL AND METHODS: Using data of 643,288 primiparous women from the German perinatal statistics of 1995-2000, we aimed to investigate this relationship. We also analyzed our data according to daily cigarette consumption. RESULTS: We found that smoking during pregnancy was strongly associated with lower birth weight and higher SGA rates. This effect was especially pronounced in women >or=31 years. There was clear dose dependence with regard to daily cigarette consumption. An increase in SGA rates in smokers versus non-smokers can already be seen for very early preterm deliveries (31 weeks of gestation or less). CONCLUSIONS: Our results allow the definition of groups of women who are at higher risk of SGA births. We show that especially older primiparous women (aged >or=31 years) who smoke >10 cigarettes a day are at increased risk of experiencing fetal growth restriction.