Impact of Prenatal Diagnosis and Elective Termination on the Prevalence of Selected Birth Defects in Hawaii

This study examined the effect of prenatal diagnosis and elective termination on the prevalence of neural tube defects, oral clefts, abdominal wall defects, and chromosomal anomalies in Hawaii by using actively ascertained surveillance data collected between 1987 and 1996 by the Hawaii Birth Defects Program. Because the Program has nearly universal access to prenatal diagnostic information and to follow-up data on elective terminations, Hawaii is an ideal setting in which to study their effects on prevalence rates of birth defects. Except for oral clefts, a large proportion of the defects studied were prenatally diagnosed: anencephaly (87%), spina bifida (62%), encephalocele (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 birth prevalence rates for most of these birth defects was significant. Including electively terminated cases in the calculations of birth prevalence rates increased the rates by more than 50% for five of the 10 birth defects studied. Am J Epidemiol1998; 148: 1206–11.