Recent findings indicate that high rates of cesarean delivery in older women are largely independent of pregnancy and labor complications and raise important questions about just what leads to some of these operative deliveries. Age-related issues assume ever greater importance as more women defer childbearing. The authors report a retrospective study of 28,484 singleton deliveries taking place in Aberdeen during the years 1988-1997 (12,510 primiparous and 15,974 multiparous births). The goal was to learn whether cesarean delivery and other interventions can be explained by obstetrical complications. Odds ratios for interventions (induction or augmentation of labor, epidural use, assisted delivery, cesarean section) were compared with those in women 20 to 29 years of age. The same was done for the use of maternity services; criteria for increased use included more than two prenatal scans, amniocentesis, antenatal hospital admission, admission for longer than 5 days at delivery, infant resuscitation, and admission to the neonatal unit. All obstetrical interventions increased with advancing age, particularly cesarean delivery (before and during labor), assisted delivery, labor induction, and augmentation (in primiparas only). All health services were used more by older women. On reanalysis taking relevant obstetrical complications into account, the associations between age and most interventions were somewhat altered but not eliminated. Complications did not help explain the relation between older maternal age and either the likelihood of having more than two scans or a prolonged stay at delivery. Only for antenatal admission and admission to the neonatal unit was the age relationship abolished (older multiparous women may even be at lower risk of antenatal admission). For normally presenting infants, instrumental vaginal delivery, prelabor cesarean, and intrapartum cesarean all were more frequent in older women. The relation between age and cesarean delivery was greatly weakened in multiparous women with a past history of cesarean delivery. Women with hypertensive disorders of pregnancy or antepartum bleeding showed little age-related increase in the frequency of induction. The obstetrical complications considered in this study fail to explain higher levels of intervention and health service use in older parturients, whether primiparas or multiparas.