Obstetric Risks of Pregnancy in Women Less Than 18 Years Old

Objective: To quantify the age-related risks of adverse outcome during pregnancy in women less than 18 years old.

Methods: We analyzed data from 341,708 completed singleton pregnancies in the North West Thames region between 1988 and 1997. Pregnancy outcomes were compared by age at delivery in women less than 18 years old (n = 5246) and 18-34 years old (n = 336,462); women 35 years old or older (n = 48,658) were excluded. Data are presented as percentages of women less than 18 and 18-34-year-old women, with adjusted odds ratios (OR) and 99% confidence intervals (CI).

Results: Pregnancy in women less than 18 years old was associated with increased risk of preterm labor before 32 weeks' gestation (OR 1.41, CI 1.02, 1.90), maternal anemia (OR 1.82, CI 1.63, 2.03), chest infection (OR 2.70, CI 1.21, 6.70), and urinary tract infection (OR 1.60, CI 1.11, 2.31), but less obstetric intervention. Operative vaginal delivery (OR 0. 46, CI 0.41, 0.56), elective cesarean (OR 0.47, CI 0.35, 0.65), or emergency cesarean (OR 0.45, CI 0.38, 0.53) were all less likely in women aged less than 18 years. Women less than 18 years old were no more likely to have stillbirths (OR 0.75, CI 0.42, 1.34) or small-for-gestational-age infants (OR 0.95, CI 0.82, 1.09) than women aged 18-34 years.

Conclusion: Pregnant women less than 18 years old were more likely to deliver preterm than older women. In most other respects they have less maternal and perinatal morbidity and were more likely to have normal vaginal deliveries.