Ethnicity and risk of caesarean section in a term, nulliparous New Zealand obstetric cohort.

BACKGROUND

One in four New Zealand (NZ) women undergo caesarean section (CS); however, little is understood about how ethnicity influences CS rates. Previous NZ studies do not include many of NZ's ethnic groups and have been unable to account comprehensively for clinical risk factors.

AIM

To investigate ethnicity as an independent risk factor for elective and emergency CS in nulliparous women at term. We hypothesised that compared with European, Māori and Pacific women would have a lower risk of elective CS, but there would be no ethnic differences in emergency CS.

METHODS

This was a retrospective cohort analysis of prospectively recorded maternity data at National Women's Health, Auckland, NZ from 2006 to 2009. The study population was 11 848 singleton, nulliparous, term births. Multivariable logistic regression analysis was performed for elective and emergency CS, accounting for comprehensive confounding factors.

RESULTS

The overall CS rate was 31.2% (elective 7.8%, n = 923 and emergency 23.4%, n = 2770). Compared with European ethnicity, Pacific and Chinese women had a reduced odds of elective CS (adjusted odds ratios, aOR 0.42, [95% CI 0.24-0.73] and 0.68, [0.49-0.94], respectively), while Indian women had an increased odds of emergency CS (aOR 1.54, [1.26-1.88]). Rates of elective or emergency CS for other ethnicities were similar to European.

CONCLUSIONS

After adjustment for confounding, we report ethnic differences in elective and emergency CS rates, which may be related to patient and/or care provider factors. Further prospective research is recommended to examine reasons for these ethnic differences in CS rates.