Ethnic disparities in perinatal mortality at 40 and 41 weeks of gestation

Objective: To evaluate whether maternal ethnicity affects perinatal mortality by week of gestation from 39 weeks onwards. Study design: In this cohort study, we used data from the nationwide Netherlands Perinatal Registry from 1999 until 2008. All singleton infants born between 39(+0) and 42(+6) weeks of gestation without congenital anomalies were included. We used crude and multivariate logistic regression analyses with white Europeans as the reference to calculate the adjusted odds ratios (aOR) of South Asian, African and Mediterranean women. The main outcome measure was perinatal mortality (antepartum and intrapartum/neonatal mortality within 7 days after birth). Results: We studied 1,092,255 singleton deliveries. Perinatal mortality occurred in 2315 infants (2.1 %). There was interaction between gestational age and ethnicity (P<0.0001). In week 40 (40(+0) -40(+6)) South Asian (aOR 1.9; 95 % CI 1.1 -3.4) and Mediterranean (aOR 1.3; 95 % CI 1.04 -1.7) women had an increased risk of perinatal mortality. The perinatal mortality risk became greater in week 41 for South Asian (aOR 4.5 95 % CI 2.8 -7.2), African (aOR 2.2; 95 % CI 1.4 -3.4) and Mediterranean (aOR 2.2; 95 % CI 1.8 -2.9) women, especially among small for gestational age infants. Conclusion: With increasing gestational age beyond 39 weeks, perinatal mortality risk increases more strongly among South Asian, African and Mediterranean women compared to European whites.