Birth defects (BD) are the leading cause of infant mortality in the United States. We analyzed data from the Vermont Oxford Network from 1994 and 1995 to determine the spectrum of serious BD and their impact on mortality and hospital days in infants with a birth weight of 501to 1500 grams. This Database includes infants 501to 1500 grams born at or referred to participating hospitals within 28 days of birth. BD were reported if they belonged to a list of 40 pre-defined major BD or if they were considered lethal or life-threatening. The length of stay (LOS) was the sum of the stay at all hospitals before the first discharge home.

Data on BD were available for 19,228 of the 19,254 infants reported by 147 hospitals in the Network in 1994 and 1995. Of these, 823 infants (4.3%) had BD, which were distributed as follows: Chromosomal anomalies: Trisomy 13 (1.6%), Trisomy 18 (6.1%), Trisomy 21 (6.8%), Turner syndrome(0.7%), Others (5.2%); BD of single systems: Neurologic (9.8%), Cardiovascular (11%), Gastrointestinal (13.7%), Genitourinary (5.1%), Skeletal dysplasia (4.3%), Miscellaneous single system anomalies (4.9%); Other BD: Inborn errors of metabolism (0.7%), Named sydromes, sequences and associations (18.8%) and Multiple system anomalies without recognised pattern(11.2%).

Infants with BD had a higher mean gestation (29.7 vs 28.4 weeks, p<0.001), a higher mean birth weight (1112 vs 1051 grams, p < 0.001), a higher mortality rate (57.7% vs 13%, p <0.001) and a higher rate of major surgery (28.7% vs 4.9%, p< 0.001). Amongst surviving infants, those with BD had a longer mean LOS than those without BD (75 vs 65 days, p <0.001).The mean LOS in infants who died with and without BD was 15 and 17 days respectively (p = 0.21). In the Database, infants with major BD accounted for 16.3% of all deaths and 18.9% of all major surgery but only 2.9% of all hospital days. Infants 501 - 1500 grams with major BD as defined in the Vermont Oxford Network had a high mortality and comprised approximately 1/6th of all deaths in the Database. However, because these infants with BD were infrequent, had a high mortality and died relatively early, they utilised a low proportion of total hospital days.