Objective: To determine whether the higher levels of obstetric intervention and maternity service use among older women can be explained by obstetric complications.
Design: A retrospective analysis of routinely collected data from the Aberdeen Maternity and Neonatal Databank.
Participants: All residents of Aberdeen city district delivering singleton infants at the Maternity Hospital 1988-1997 (28,484 deliveries).
Main outcome measures: Odds ratios for each intervention in older maternal age groups compared with women aged 20-29. Interventions considered include obstetric interventions (induction of labour, augmentation, epidural use, assisted delivery, caesarean section) and raised maternity service use (more than two prenatal scans, amniocentesis, antenatal admission to hospital, admission at delivery of more than five days, infant resuscitation, and admission to the neonatal unit).
Methods: Logistic regression was used to investigate the association between maternal age and the incidence of interventions. The odds ratios for each intervention were then adjusted for relevant obstetric complications and maternal socio-demographic characteristics.
Results: Levels of amniocentesis, caesarean section, assisted delivery, induction, and augmentation (in primiparae) are all higher among older women. Maternity service use also increases significantly with age: older women are more likely to have an antenatal admission, more than two scans, a hospital stay at delivery of more than five days, and have their baby admitted to a neonatal unit. Controlling for relevant obstetric complications reveals several examples of effect modification, but does not eliminate the age effect for most interventions in most groups of women.
Conclusions: Higher levels of intervention among older women are not explained by the obstetric complications we considered.