Adolescent smoking in pregnancy and birth outcomes

Introduction: Cigarette smoking amongst pregnant adolescents is a preventable risk factor associated with low birthweight (< 2500 g), preterm birth (< 37 weeks) and infant mortality. The aim of this study was to compare birth outcomes of adolescents who smoke during pregnancy with those who do not and to construct their birthweight-for-gestational-age curves. Methods: A retrospective cohort analysis of 534 adolescents (<= 19 years) and 8972 adults who delivered singleton births between 1998-2003 at the Liverpool Women's Hospital. Results: Adolescent pregnancy occurred in 5.6% of deliveries. Mean age of adolescents was 18.1 years (SD = 1.0) and 46.2% smoked during pregnancy including 83.5% light smokers (< 10 cigarettes daily). Babies born to adolescent smokers were significantly lighter by -170 g (P = 0.005). The prevalence of low birthweight was almost double in adolescents who smoked (12.1% versus 6.8%, RR = 1.7; CI = 1.0- 3.0), and their mean Apgar scores at 5 min were lower (< 0.05). A higher prevalence of preterm birth (P < 0.05) and maternal anaemia (P < 0.01) occurred amongst adolescent smokers. Adolescents smoking > 10 cigarettes daily had babies with larger birthweight reduction (P 0.001). Conclusion: Almost half of all adolescents smoked during their pregnancy. Birthweight- for- gestationalage curves of smoking adolescents showed a marked fall- off in weight from 36 weeks of gestation, and at least 10% of adolescent smokers showed fetal growth restriction from before 32 weeks of gestation.