Gestational Age and Socioeconomic Achievements in Young Adulthood: A Danish Population-Based Study

IMPORTANCE: The poor health outcomes associated with preterm birth are well established. However, it is less clear how small variations in gestational age, even within the term range, are associated with long-term opportunities and well-being, as measured by socioeconomic outcomes in adulthood. OBJECTIVE: To examine the association of gestational age at birth with educational achievement, income, and primary source of income in adulthood. DESIGN, SETTING, AND PARTICIPANTS: This Danish population-based, register-based cohort study examined all live-born singletons born in Denmark from 1982 to 1986 without congenital anomalies and who lived in Denmark at age 28 years. Data analysis was conducted from November 2, 2017, to June 15, 2018. EXPOSURES: Gestational age at birth in completed weeks (22-45 weeks). MAIN OUTCOMES AND MEASURES: Educational attainment, personal income, and primary source of income at age 28 years. RESULTS: In a population of 228 030 singletons (4.0% preterm, 12.1% early term; 49.4% female), 36.3% had a tertiary education at age 28 years. Among adults born at 22 to 27 weeks of gestation, 21.6% had a tertiary education, and 23.2% had an income in the highest tertile. Using 40 weeks of gestation as the reference, the adjusted odds ratio for tertiary education for individuals born at 22 to 27 weeks of gestation was 0.21 (95% CI, 0.13-0.35) and the corresponding figures for 28 to 31, 33, 36, 38, and 43 to 45 weeks of gestation were 0.45 (95% CI, 0.37-0.55), 0.67 (95% CI, 0.54-0.83), 0.84 (95% CI, 0.77-0.93), 0.85 (95% CI, 0.81-0.89), and 0.93 (95% CI, 0.83-1.04), respectively. The adjusted odds ratio for highest income tertile for individuals born at 22 to 27 weeks of gestation was 0.66 (95% CI, 0.41-1.06) and the corresponding figures for 28 to 31, 33, 36, 38, and 43 to 45 weeks of gestation were 0.80 (95% CI, 0.68-0.94), 0.77 (95% CI, 0.63-0.93), 0.89 (95% CI, 0.82-0.96), 0.95 (95% CI, 0.91-0.99), and 1.00 (95% CI, 0.91-1.12), respectively. All estimates were adjusted for sex, birth year, parity, maternal age, maternal education, and maternal country of origin. CONCLUSIONS AND RELEVANCE: Shorter gestational duration even within the term range was associated with poorer socioeconomic outcomes in adulthood. While adults born at 35 to 38 weeks of gestation experienced only slightly increased risk of adverse socioeconomic outcomes, this may have a significant impact on public health, since a large proportion of all children are born in these weeks.