Data from 44,386 pregnancies were analyzed to determine if advancing maternal age influences frequency or outcome of antenatal disorders. The perinatal mortality rate progressively increased from 25/1000 at age 17 ro 19 years to 69/1000 after age 39. Stillbirths accounted for 92% of this increase. Fourteen percent of the increase was due to congenital malformations and 50% to disorders associated with uteroplacental underperfusion, ie, abruptio placentae, large placental infarcts, and placental growth retardation. Sclerotic lesions in the myometrial arteries are a possible cause of underperfusion because the proportion of arteries with these lesions increased from 11% at age 17 to 19 years to 83% after age 39.