A retrospective cohort study of mortality among children with birth defects in New York State, 1983-2006

Birth defects, which occur in about 3% of live births in the United States each year, have remained the leading cause of infant mortality, although the infant mortality rate in the United States has decreased significantly over the past decades. The objective of this study was to conduct a retrospective cohort study with long-term follow-up of the children in New York State Congenital Malformations Registry (CMR) for up to 24 years on their mortality status to evaluate the mortality risk of children with birth defects by age at death, birth defect category and other possible contributing factors.

Children born in 1983-2006 with reportable birth defects were included in the study cohort. A sub-cohort was also constructed containing children born in 1983-2006 with selected major birth defects that are relatively severe congenital conditions identified at birth. New York State live births in 1983-2006 were used as the comparison population. The deaths among the study cohort were identified through linking CMR cases to the death certificate files. A Poisson regression model was used to calculate mortality rate ratios (mortality risk) adjusting for selected infant and maternal risk factors.

Compared to children without birth defects, the overall mortality risk was 6.7 times higher for children with any of the reportable birth defects and 23.6 times higher for children with selected major birth defects. The mortality risk decreased with increasing age of children. The top 5 most significantly high mortality risks were found among infants in neonatal period with anencephaly (RR = 200.5, 95% CI:180.6-222.5) and renal agenesis/dysgenesis (RR = 69.5, 95% CI:64.2-75.2), and among children aged 1-2 years with Trisomy 18 (RR = 206.4, 95% CI:28.5-331.6), Trisomy 13 (RR = 157.3, 95% CI:83.5-296.4), and hypoplastic left heart (RR = 161.5, 95% CI:20.1-217.2). Low birth weight and gestational age, multiple malformations and high lethality of anomalies involved were the major contributors to the high risk of mortality among children with selected major birth defects compared to those without birth defects.

Using the state-wide, population-based birth defects surveillance data to conduct a long-term follow-up of a large cohort of New York children, we were able to examine mortality and survival experience of the affected children during infancy and childhood period by individual birth defects of interest. As expected, children born with birth defects had a higher risk of mortality compared to children without birth defects. The magnitude of the risk varied by children's age, birth and maternal characteristics and the lethality of the specific birth defects involved.