[1] Univ Arkansas Med Sci, Dept Pediat, Arkansas Ctr Birth Defects Res & Prevent, Coll Med, Little Rock, AR 72202 USA
[2] Arkansas Childrens Hosp, Little Rock, AR 72202 USA
[3] Univ Arkansas Med Sci, Dept Pediat, Ctr Appl Res & Evaluat, Coll Med, Little Rock, AR 72202 USA
[4] Univ Arkansas Med Sci, Dept Hlth Policy & Management, Coll Publ Hlth, Little Rock, AR 72202 USA
[5] New York State Dept Hlth, Congenital Malformat Registry, Troy, NY USA