Advanced maternal age is an independent risk factor for intrauterine growth restriction.

Reports on the association between advanced maternal age (AMA) and intrauterine growth restriction (IUGR) are conflicting. Our objective was to determine if AMA is an independent risk factor for IUGR. Our case-control study compared cases with IUGR (birthweight<10th percentile for gestational age) and a control group without IUGR. Gestational ages were all confirmed by ultrasound. The study included only singletons and fetal anomalies were excluded. Both groups were evaluated for maternal demographics and clinical risk factors. AMA was defined as maternal age>35 years. Univariate and multivariate analyses were used to examine associations. During the study period, there were 824 cases with IUGR meeting the inclusion criteria; these were compared with 1648 controls (no IUGR) randomly selected from the same population during the same study period. The significant factors associated with IUGR multivariate analyses were black race (odds ratio [OR], 22.4; 95% confidence interval [CI], 17.8 to 28); chronic hypertension (OR, 2.2; 95% CI, 1.5 to 3.2); pregestational diabetes (OR, 3.3; 95% CI, 1.6 to 7) illicit drug use (OR, 3.3; 95% CI, 2.2 to 5.2), and AMA (OR, 1.4; 95% CI, 1.1 to 1.8). There was a positive dose-response association between increasing maternal age and increasing risk for IUGR. At maternal age of 40 years or older, the OR and 95% CI for IUGR was 3.2 and 1.9 to 5.4, respectively. AMA is an independent risk factor for IUGR. Our findings suggest that screening for IUGR is indicated in women age 35 years or older.