Objective In recent years, the proportion of pregnant women who are 35 or older, that is, those of advanced maternal age (AMA), has steadily increased, and the pregnancy-associated risks have become increasingly prominent. However, studies focusing on pregnancy outcomes among women aged 30 to 35 years remain limited. This study aimed to compare pregnancy complications and adverse outcomes across different maternal age groups.

Methods women with singleton pregnancies were enrolled. All participants received prenatal care and gave birth at a tertiary hospital between January 2022 and December 2024. According to the maternal age at the time of delivery, the participants were divided into 4 groups, appropriate age group Ⅰ or simply age group Ⅰ (< 30 years), appropriate age group Ⅱ or simply age group Ⅱ (30 to < 35 years), AMA group (35 to < 40 years), and very AMA Group (≥ 40 years). One-way analysis of variance (ANOVA), χ² tests, and multivariate logistic regression models were used to evaluate the effect of maternal age on pregnancy outcomes, with adjustment made for confounding factors, including body mass index (BMI) at registration for prenatal care, gestational weight gain during the second and third trimesters, parity, and polycystic ovary syndrome.

Results As maternal age increased, the incidence of multiple adverse outcomes rose progressively. Multivariable logistic regression analysis showed that, compared with age group Ⅰ, the odds ratios (ORs) (95% CIs) for gestational diabetes mellitus in age group Ⅱ, AMA group, and very AMA Group were 1.37 (1.29, 1.44), 1.98 (1.85, 2.11), and 3.11 (2.74, 3.54), respectively. The corresponding ORs (95% CIs) for preeclampsia were 1.21 (1.07, 1.38), 1.87 (1.60, 2.18), and 4.06 (3.18, 5.19), respectively; those for gestational hypertension were 1.31 (1.12, 1.52), 1.76 (1.45, 2.12), and 2.90 (2.13, 3.96), respectively; those for placenta previa were 1.56 (1.27, 1.91), 2.52 (1.99, 3.18), and 4.77 (3.41, 6.66), respectively; and those for delivery by cesarean section were 1.32 (1.27, 1.37), 2.33 (2.19, 2.47), and 5.49 (4.68, 6.44), respectively. In addition, compared with age group Ⅰ, the ORs (95% CIs) for fetal chromosomal abnormalities were 2.27 (1.68, 3.06) in the AMA group and 3.91 (2.46, 6.22) in the very AMA Group.

Conclusion Maternal age is positively associated with pregnancy complications and adverse pregnancy outcomes. The risk increases significantly after age 30 and becomes particularly pronounced in women aged ≥40 years. Enhanced periconceptional health management, early screening, and intervention for women aged ≥ 30 are warranted to reduce the risk of pregnancy complications and improve maternal and neonatal outcomes.