Impact of prenatal diagnosis and elective termination on the prevalence ofselected birth defects in Hawaii

This study examined the effect of prenatal diagnosis and elective terminati on on the prevalence of neural tube defects, oral clefts, abdominal wall de fects, and chromosomal anomalies in Hawaii by using actively ascertained su rveillance data collected between 1987 and 1996 by the Hawaii Birth Defects Program. Because the Program has nearly universal access to prenatal diagn ostic information and to follow-up data on elective terminations, Hawaii is an ideal setting in which to study their effects on prevalence rates of bi rth defects. Except for oral clefts, a large proportion of the defects stud ied were prenatally diagnosed: anencephaly (87%), spina bifida (62%), encep halocele (83%), cleft palate (0%), cleft lip with or without cleft palate ( 14%), omphalocele (60%), gastroschisis (76%), Down syndrome (43%), trisomy 18(61%), and trisomy 13(40%). The effect of elective terminations on the bi rth prevalence rates for most of these birth defects was significant. Inclu ding electively terminated cases in the calculations of birth prevalence ra tes increased the rates by more than 50% for five of the 10 birth defects s tudied.