Neonatal mortality rates in communities with small maternity units compared with those having larger maternity units

Objective To compare neonatal mortality in geographical areas where most deliveries occur in large hospitals with areas where a larger proportion of deliveries occur in small maternity units. Design Population-based study using data from The Norwegian Medical Birth Registry. Setting Records on all deliveries in Norway from 1967 to 1996, a total of 1.7 million births, were equipped with data on the size of the maternity units used by delivering women in that particular area. Main outcome measure Risk of neonatal death. Results Women living in areas where the most frequently used delivery unit had less than 2000 annual deliveries had 1.2 fold the risk of experiencing neonatal death of their newborn (95% CI 1.1-1.3). The relative risk of neonatal death in geographical areas where more than 75% of deliveries occurred in units with more than 3000 annual births was 0.8 (95% CI 0.7-0.9) compared with areas where none delivered in such large units. The relative risk of neonatal death in areas where the most frequently used delivery units had less than 100 annual births was 1.4 (95% CI 1.1-1.7) compared with areas where units of more than 3000 annual births were the most frequently used. Differences in outcome could not be explained by differences in travelling distance to an urban centre where most referral delivery units are located, differences between rural and urban municipalities, or by differences in biological or socio-economic risk factors between municipalities. Conclusions We observed a small but significantly decreased neonatal mortality in areas where the great majority of births occurred in large hospitals.