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

Cragan, Janet D.; Roberts, Helen; Edmonds, L D; Khoury, Muin J.; Kirby, Robert R.; Shaw, Gary M.; Velie, Ellen M.; Merz, Ruth D.; Forrester, Mathias B.; Williamson, R A; Krishnamurti, Diane; Stevenson, Roger E.; Dean, Jane H.

doi:10.1002/(sici)1096-9926(199707/08)56:1/2<37::aid-tera8>3.3.co;2-n

Cited by 47 publications

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“…Further, within-country differences have been observed between racial and ethnic groups. For example, in the USA, Hispanics have higher spina bifida prevalence 8, and African-Americans have lower prevalence 9, compared with non-Hispanic whites. Prevalence differences in time and across geographic regions have been attributed to variations in ascertainment methods as well as to true differences in risk.…”

Section: Epidemiologymentioning

confidence: 99%

Spina bifida

Copp

Adzick

Chitty

et al. 2015

Nat Rev Dis Primers

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Spina bifida is a birth defect in which the vertebral column is open (bifid), often with spinal cord involvement. Clinically most significant is myelomeningocele (MMC; open spina bifida) in which the spinal neural tube fails to close during embryonic development. The exposed neural tissue degenerates in utero, resulting in neurological deficit that varies with level of the lesion. Occurring in around 1 per 1000 births worldwide, MMC is one of the commonest congenital malformations, yet its causation is largely unknown. The genetic component of MMC is estimated at 60-70% but few genes have yet been identified, despite much information from mouse models. Non-genetic risk factors include reduced folate intake, maternal anticonvulsant therapy, diabetes mellitus and obesity. Primary prevention by peri-conceptional folic acid has been demonstrated in clinical trials, leading to food fortification programmes in many countries. Prenatal diagnosis is by ultrasound enabling termination of pregnancy. Individuals who survive to birth have their lesions closed surgically, with subsequent management of associated defects, including the Chiari II malformation, hydrocephalus, and urological and orthopaedic sequelae. Fetal surgical repair of MMC has been associated with improved early neurological outcome compared with postnatal operation. MMC affects quality of life during childhood, adolescence, and into adulthood, posing a challenge for individuals, families and society as a whole.

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Section: Epidemiologymentioning

confidence: 99%

Spina bifida

Copp

Adzick

Chitty

et al. 2015

Nat Rev Dis Primers

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523

432

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“…Neural-tube defects (NTD) are among the most common birth defects reported worldwide, with a declining US-incidence of 2-3/1000 in 1970, to 1/1000 in 1990 Cragan et al, 1995). Despite considerable dedicated effort and the discovery in mice of several genes causing NTD, no gene(s) causing NTD have been found in humans (Rozen, 1996;Motulsky, 1996).…”

Section: Introductionmentioning

confidence: 99%

Neural-tube defects are associated with low concentrations of cobalamin (vitamin B12) in amniotic fluid

et al. 1998

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“…Studies have found substantial differences in the estimated prevalence of many types of birth defects depending on whether cases among terminated pregnancies are included or not and depending on the source used to ascertain these cases (e.g., hospitals vs. prenatal clinics) (13, 17, 18). Even with multiple sources of ascertainment, birth defects surveillance programs typically cannot achieve complete case ascertainment among terminated pregnancies, and the proportion of cases missed remains unknown but is likely substantial for some defects such as spina bifida.…”

Section: Discussionmentioning

confidence: 99%

“…Several potential mechanisms have been posited (1–4), including bias due to incomplete ascertainment of cases among terminated pregnancies (5–13). Because ascertainment of terminated pregnancies is more difficult than ascertainment of live births and stillbirths, selection bias can occur when prenatal diagnosis of a birth defect increases the probability of termination, and termination differs by exposure status (6, 9).…”

Section: Introductionmentioning

confidence: 99%

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Adjusting for Bias Due to Incomplete Case Ascertainment in Case-Control Studies of Birth Defects

Howards¹,

Johnson²,

Honein³

et al. 2015

Am. J. Epidemiol.

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Case-control studies of birth defects might be subject to selection bias when there is incomplete ascertainment of cases among pregnancies terminated following prenatal diagnosis of the defect. We propose a simple method to estimate inverse probability of selection weights (IPSWs) for cases ascertained from pregnancies both ending and not ending in termination using data directly available from the National Birth Defects Prevention Study and other published information. The IPSWs can then be used to adjust for selection bias analytically. We can also allow for uncertainty in the selection probabilities through probabilistic bias analysis. We provide an illustrative example using data from National Birth Defects Prevention Study (1997–2009) to examine the association between prepregnancy obesity (body mass index ≥30 vs. <30 kg/m2) and spina bifida. The unadjusted odds ratio (OR) for prepregnancy obesity and spina bifida is 1.48 (95% confidence interval: 1.26, 1.73), and the simple selection bias-adjusted OR is 1.26 (95% confidence interval: 1.04, 1.53). The probabilistic bias analysis resulted in a median adjusted OR of 1.22 (95% simulation interval: 0.97, 1.47). The proposed method provides a quantitative estimate of the IPSWs and the bias introduced by incomplete ascertainment of cases among terminated pregnancies conditional on a set of assumptions.

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

Cited by 47 publications

References 0 publications

Spina bifida

Spina bifida

Neural-tube defects are associated with low concentrations of cobalamin (vitamin B12) in amniotic fluid

Adjusting for Bias Due to Incomplete Case Ascertainment in Case-Control Studies of Birth Defects

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