Epidemiologic paradox in multiple births among Asians in Illinois. Correlation between risk factors and outcomes

To determine if the plural birth rate, maternal risk factors and neonatal outcomes among Asian American populations residing in Illinois are homogeneous or heterogeneous with regard to maternal risk factors and neonatal outcomes and to attempt to establish correlations between maternal risk factors and neonatal outcomes.

A total of 1,145,962 computerized birth certificate files were analyzed for 11 Asian subgroups giving birth in Illinois in the years 1989-1994.

The multiple birth rates varied between 6 per 1,000 (Vietnamese) to 15 per 1,000 (Cambodian) (heterogeneity among all groups, P < .005). The percent of neonates born at gestational ages 22-33 weeks varied between 0 (Cambodian) to 28 (Thai). Japanese women showed the highest rate of neonates with birth weight less than 2,500 g after adjustment for race: 15.38 per 1,000. Women from Cambodia and Laos had the highest sum of maternal risk factors; those from the Philippines and Thailand had the least. The lowest collective adverse neonatal outcomes were in infants born to women from Cambodia and Laos.

The 11 subgroups of Asians living in Illinois demonstrate heterogeneity with respect to multiple birth rate, selected maternal risk factors and adverse neonatal outcomes. After considering all maternal risk factors and neonatal outcomes, the two groups (Cambodians and Laotians) with the poorest maternal risk factors had the lowest rate of poor neonatal outcomes. This is the first time that this epidemiologic paradox has been observed in twins of Asian ancestry.