These babies have multiple birth defects and usually die in the first months of life. Heart defects are the most common type of structural birth defect, affecting one baby in 125. While advances in surgical treatment have dramatically improved the outlook for babies with heart defects, these remain the leading cause of birth defect-related infant deaths. Doctors usually do not know what causes a baby's heart to form abnormally, though genetic and environmental factors are believed to play a role. Every baby's spine is open when it first forms, but it normally closes by the 29th day after conception.
Affected babies suffer varying degrees of paralysis, and bladder and bowel problems.
Both genetic and nutritional factors appear to play a role in spina bifida. About one baby in 135 has a structural defect involving the genitals or urinary tract. The cause of hypospadias, which is surgically correctable, in unknown. Babies who lack both kidneys die in the first hours or days of life. This tragic defect is sometimes inherited.