[Effect of maternal age on pregnancy outcomes in Beijing]

Objective: To evaluate the maternal age at delivery in Beijing and the effect of maternal age on pregnancy outcomes. Methods: A retrospective analysis was conducted on 14 970 singleton pregnancies from 15 hospitals in Beijing from June 20(th) to November 30(th) in 2013. These hospitals were sorted by the numbers of delivery and chosen as clusters by systemic cluster sampling method. The data of age, diagnosis with gestational diabetes mellitus (GDM) and pre-eclampsia (PE), neonatal birth weight, gestational age at delivery, postpartum hemorrhage and infants admitted to the neonatal ICU (NICU) were collected. The 14 970 women were divided into 5 groups according to their ages at delivery: (1) less than 20 years (n=205), (2)20-<30 years (n=9 228), (3)30-<35 years (n=4 365), (4)35-<40 years (n=1 017), and(5) 40 years and older (n=155). T-test and χ(2) test were used for between-group comparison, and logistic regression analysis was used to examine the association between age and the risk of adverse pregnancy outcomes. Results: (1) The mean maternal age at delivery in 2013 in Beijing was (28±4) years old. Among them, 205 (1.4%, 205/14 970) delivered under 20 years of age; 1 172 (7.8%, 1 172/14 970) ≥35 years; and 155 (1.0%, 155/14 970) at 40 years and older. (2) The prevalence of diabetes, hypertension, overweight and obesity increased with age, and the incidence of these conditions were 3.4%, 4.3% and 31.4% in women with advanced age, respectively. (3) Compared with 20-<30 years group, less than 20 years was associated with significantly lower incidence of GDM [adjust OR (aOR)=0.393, 95%CI: 0.222-0.696] and cesarean section rate (aOR=0.549, 95%CI: 0.391-0.771), and higher incidence of preterm birth (aOR=2.144, 95%CI: 1.256-3.662). Moreover, 30-<35 years, 35-<40 years and 40 years and older groups all had significantly higher risk of GDM (30-34 years, aOR=1.513, 95%CI: 1.374-1.666; 35-<40 years, aOR=2.094, 95%CI: 1.786-2.455; ≥40 years, aOR=2.174, 95%CI: 1.492-3.167), preterm birth (aOR=1.219, 95%CI: 1.021-1.455; aOR=1.644, 95%CI: 1.251-2.161; aOR=2.141, 95%CI: 1.209-3.792), cesarean section (aOR=1.373, 95%CI: 1.268-1.486; aOR=2.960, 95%CI: 2.550-3.435; aOR=4.332, 95%CI: 2.920-6.426) and NICU admission rate (aOR=1.236, 95%CI: 1.059-1.443; aOR=1.337, 95%CI: 1.018-1.756; aOR=2.389, 95%CI: 1.385-4.121), when compared to the 20-<30 years of age group. Higher incidence of PE (aOR=1.292, 95%CI: 1.007-1.659) and postpartum hemorrhage (aOR=1.224, 95%CI: 1.048-1.429) were also noted in women of 30-<35 years, compared to 20-<30 years group respectively. Conclusion: Both advanced maternal age and adolescent pregnancy are associated with increasing risk of adverse pregnancy outcomes.