OBJECTIVE: To determine if the rates of pregnancy complications, preterm birth, small for gestational age, perinatal mortality, and serious neonatal morbidity are higher among mothers aged 35- 39 years or 40 years or older, compared with mothers 20- 24 years. METHODS: We performed a population- based study of all women in Nova Scotia, Canada, who delivered a singleton fetus between 1988 and 2002 (N = 157,445). Family income of women who delivered between 1988 and 1995 was obtained through a confidential linkage with tax records (n = 76,300). The primary outcome was perinatal death (excluding congenital anomalies) or serious neonatal morbidity. Analysis was based on logistic models. RESULTS: Older women were more likely to be married, affluent, weigh 70 kg or more, attend prenatal classes, and have a bad obstetric history but less likely to be nulliparous and to smoke. They were more likely to have hypertension, diabetes mellitus, placental abruption, or placenta previa. Preterm birth and small- for- gestational age rates were also higher; compared with women aged 20- 24 years, adjusted rate ratios for preterm birth among women aged 35- 39 years and 40 years or older were 1.61 (95% confidence interval [CI] 1.42- 1.82; P < .001) and 1.80 (95% CI 1.37- 2.36; P < .001), respectively. Adjusted rate ratios for perinatal mortality/morbidity were 1.46 (95% CI 1.11- 1.92; P = .007) among women 35- 39 years and 1.95 (95% CI 1.13- 3.35; P = .02) among women 40 years or older. Perinatal mortality rates were low at all ages, especially in recent years. CONCLUSION: Older maternal age is associated with relatively higher risks of perinatal mortality/morbidity, although the absolute rate of such outcomes is low. OBJECTIVE: To determine if the rates of pregnancy complications, preterm birth, small for gestational age, perinatal mortality, and serious neonatal morbidity are higher among mothers aged 35- 39 years or 40 years or older, compared with mothers 20-24 years. METHODS : We performed a population-based study of all women in Nova Scotia, Canada, who delivered a singleton fetus between 1988 and 2002 (N = 157,445). Family income of women who delivered between 1988 and 1995 was obtained through a confidential linkage with tax Results were based on logistic models. RESULTS: Older women were more likely to be married, affluent, weigh 70 kg or more, attend prenatal classes, and have a bad obstetric history but less likely to be nulliparous and to smoke. They were more likely to have hypertension, diabetes mellitus, placental abruption, or placenta previa. Preterm birth a nd small- for-gestational age rates were also higher; compared with women aged 20-24 years, adjusted rate ratios for preterm birth among women aged 35- 39 years and 40 years or older were 1.61 (95% confidence interval [CI] 1.42 Adjusted rate ratios for perinatal mortality / morbidity were 1.46 (95% CI 1.11-1.92; P = .007) among 1.80; P <.001) and 1.80 (95% CI 1.37-2.66; P <.001) Women 35-39 years and 1.95 (95% CI 1.13- 3.35; P = .02) among women 40 years or older. Perinatal mortality rates were low at all ages, especially in recent years. CONCLUSION: Older maternal age is associated with relatively advanced higher risks of perinatal mortality / morbidity, though the absolute rate of such outcomes is low.