Figure 1.

Predicted absolute risks (with 95% confidence intervals) of adverse pregnancy and birth outcomes at specified values of maternal age at first birth in British Columbia (Canada), 2004–2014 (n=203,414). Unadjusted and adjusted risks according to maternal age at first birth: i) gestational diabetes mellitus; ii) hypertensive disorders of pregnancy; iii) cesarean delivery; iv) preterm delivery; v) spontaneous preterm delivery; vi) indicated preterm delivery; vii) multiple gestations; viii) major congenital anomaly; ix) small-for-gestational age; x) NICU stay >=2 days; xi) stillbirth; xii) neonatal mortality; xiii) infant mortality; xiv) maternal mortality or near-miss morbidity; xv) severe adverse fetal-infant composite; xvi) health pregnancy and delivery composite.

Models for gestational diabetes were restricted to those without pre-pregnancy type 1 or type 2 diabetes mellitus. Models for NICU stay ≥2 days restricted to births after April, 2008. Models for small-for-gestational age restricted to singleton pregnancies and gestational ages from 22 to 43 weeks. Adjusted models included pre-pregnancy diabetes, pre-pregnancy chronic hypertension, pre-pregnancy body mass index, smoking, indicator variables for calendar year, inadequate prenatal care, low income, rural residence, previous spontaneous or therapeutic abortion, diagnosed infertility, infertility treatment.

Maternal age at first birth was modeled using restricted cubic splines with 4 knots (at the 5th, 35th, 65th, and 95th percentiles; ages 19.7, 27.1, 31.5, and 38.6) for hypertensive disorders of pregnancy, gestational diabetes, cesarean delivery, spontaneous preterm delivery, and healthy preterm delivery and modeled using restricted cubic splines with 3 knots (at the 10th, 50th, and 90th percentiles; ages 21.4, 29.3, and 36.5) for all other outcomes.