Surveillance for Anencephaly and Spina Bifida and the Impact of Prenatal Diagnosis—United States, 1985–1994

Abstract

Problem/Condition: The reported prevalence of anencephaly and spina bifida in the United States has steadily declined since the late 1960s. During this time, the ability to diagnose these defects prenatally has progressed rapidly. Many U.S. birth defects surveillance systems ascertain defects only among live-born infants or among infants and fetuses beyond a certain gestational age, thus excluding defects among pregnancies prenatally diagnosed as being affected by a neural tube defect (NTD) and electively terminated before the gestational age limit. The impact of prenatal diagnosis and subsequent pregnancy termination on the reported prevalence of anencephaly and spina bifida in the United States has not been well established. However, assessment of this impact is crucial to the use of surveillance data to monitor trends in the occurrence of NTDs and the effectiveness of interventions for these defects (e.g., increased consumption of folic acid).Surveillance for Anencephaly and Spina Bifida and the Impact of Prenatal Diagnosis --United St...

Effect of Prenatal Diagnosis on Epidemiologic Studies of Birth Defects

“…This estimate was taken from a study of the effect of prenatal diagnosis on neural tube defect rates on the data of the Metropolitan Atlanta Congenital Defects Program, an active surveillance system for birth defects in the same population, from 1990 through 1991. 7 To assess the bias when S 1 Ͻ S 2 , we also used data from the Metropolitan Atlanta Congenital Defects Program for 1990 -1991 7 to evaluate the effect of prenatal diagnosis and elective termination on the relation between race and the risk of having a pregnancy affected by anencephaly. In these data, 64% of pregnancies with anencephaly among white women were terminated compared with 38% of such pregnancies among black women.…”

“…This estimate was taken from the data of the Metropolitan Atlanta Congenital Defects Program for 1990 -1991. 7 We also assumed a 17% reduction in physicians' ability to diagnosis spina bifida prenatally among obese women. This estimate was taken from a 1988 study of a population in Michigan.…”

“…Table 2 shows the differential effect (S 1 Ͻ S 2 ) of prenatal diagnosis and elective termination on the relation between race and the risk of anencephaly. 7 The 64% estimate of termination among pregnancies with anencephaly was applied to the data for white women, and the 38% estimate of termination among such pregnancies was applied to the data for black women. This difference resulted in the OR being biased toward the null (1.33 vs 2.30) when prenatally diagnosed pregnancies were not included in the case ascertainment, although with a slightly narrower 95% CI.…”

“…[7][8][9] Because such terminations may occur outside the in-patient hospital setting, studies of neural tube defects that ascertain defects only among infants born in hospitals systematically exclude these pregnancies. A variety of factors may influence whether a congenital defect is diagnosed prenatally and how an affected pregnancy is managed.…”

Myelomeningocele: surgical trends and predictors of outcome in the United States, 1988–2010

“…When myelomeningocele with or without additional birth defects is diagnosed sufficiently early in pregnancy, 3%-29% of women in the United States, depending on hospital region, choose to terminate pregnancy. 16 The estimated number of myelomeningocele surgical cases during 2007-2010 is 860. From a neurosurgical training perspective, given the number of residency training programs in the United States, this number highlights the difficulty of providing adequate exposure to the surgical treatment of myelomeningocele during residency.…”