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

Abstract

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.

PIP: A surveillance study was conducted to examine the effects of prenatal diagnosis and elective terminations on the prevalence of neural tube defects (NTDs), oral clefts, abdominal wall defects, and chromosomal anomalies in Hawaii. The analysis involved 10 years of data collected through the Hawaii Birth Defects Program during 1987-96; the data comprised all reported cases of anencephaly, spina bifida, encephalocele, cleft palate, cleft lip with or without cleft palate, omphalocele, gastroschisis, Down syndrome, trisomy 18, and trisomy 13. Findings showed that there were 211 infants with NTDs (87% anencephaly, 62% spina bifida, and 83% encephalocele), 376 infants with oral cleft (14% cleft lip with or without cleft palate), 117 with abdominal wall defects (60% omphalocele and 76% gastroschisis), and 449 chromosomal anomalies (43% Down's syndrome, 61% trisomy 18, and 40% trisomy 13). Prenatal diagnosis and elective pregnancy terminations have a significant impact on the birth prevalence rates of NTDs and chromosomal anomalies. These finding have important implications for other birth defects surveillance programs.