Associations between ethnicity and obstetric intervention in New Zealand

To determine whether the lower rates of obstetric interventions in Maori and Pacific Island women from the New Zealand Ministry of Health obstetric procedures report in 1999 existed also in National Women's Hospital (NWH), Auckland data and if so whether they persisted after controlling for parity and obstetric risk.

The study population included 43,367 singleton, cephalic deliveries, not preceded by caesarean section at NWH from 1992-1999. Ethnicity was Maori, Pacific Island, or other. Obstetric interventions were explored at two time points: (1) at the initiation of the delivery process: induction of labour, prelabour caesarean section, or spontaneous onset of labour; and (2) at the point of delivery: either caesarean section, operative vaginal delivery, or spontaneous vaginal birth. Independent associations were found by fitting polytomous logistic regression models.

10% of the study population were Maori, 19% Pacific Islanders, and 71% other. Unadjusted analyses showed lower rates of all obstetric interventions for Maori and Pacific Island women. Adjusted analyses showed that rates of induction of labour, prelabour caesarean, and operative vaginal delivery were lower for Maori and Pacific women than for all other ethnicities grouped together. However, caesarean delivery rates overall were not different for Maori or Pacific Island women.

The adjusted analysis did not confirm the association seen in the New Zealand Ministry data between ethnicity and caesarean section. However, induction, prelabour caesarean section, and operative vaginal delivery were less common in Maori and Pacific Island women.