Increased risk of birth defects among children from multiple births.

Background: Multiple births are increasing, and may be associated with birth defects.
Methods: To explore this relationship, data from the Virginia birth defects registry (VaCARES) was analyzed.
Results: During 1989-1998, a total of 44505 children from singleton births and 2258 children from multiple births were born with birth defects in Virginia. The risk of birth defects was significantly increased in children from multiple births as compared to singleton births (birth defect rate per 10000 live births: singleton 482.3, twin 922.0, triplet 1300.0, and quadruplet or higher 2222.2). Increased risk was observed for 39 of 86 diagnoses. The five diagnoses with the highest risk ratio per 10000 live births (RR) were: neurofibromatosis (RR, 12.80), retrolental fibroplasia (RR, 9.96), microphthalmos (RR, 5.24), pulmonary valve anomalies (RR, 5.00), and patent ductus arteriosus (RR, 4.68). A significantly reduced risk ratio for congenital hip dislocation was found in these children (RR, 0.54). In most multiple births, only one child was born with birth defects (81% in twin births, 71% in triplet births, and 56% in quadruplet and higher births). The diagnosis of birth defects might be concordant or discordant for children in which all siblings had birth defects. The children from multiple births who had birth defects were generally preterm and had significantly lower birth weight. A higher fatality and mortality rate and longer hospital stay were also observed.
Conclusions: Overall, children from multiple births have an increased risk of birth defects.
(Copyright 2003 Wiley-Liss, Inc.)