Studies in neural tube defects I. Epidemiologic and etiologic aspects

Abstract

In the NIH Collaborative Perinatal Project, a prospective study of over 53,000 pregnant women and their offspring, 71 single-born children (13.33/10,000) were found to have a non-syndromal neural tube defect (NTD). A family history was present in only one case. The group of individuals with NTD was compared to a group of 400 randomly selected non-malformed control infants. Of over 50 maternal factors studied the following showed significant association with NTD in the offspring: diabetes mellitus; organic heart disease; lung disease; and diuretic, antihistamine, and sulfonamide use. The interval between the termination of the immediately previous pregnancy and the start of the proband pregnancy was significantly shorter in mothers of NTD children than in mothers of control infants. The risk for NTD was also significantly increased if the immediately previous pregnancy was a spontaneous abortion. There was no increased risk for NTDs among sibs of children with major malformations such as tracheo-esophageal "dysraphism," cleft lip/palate, or renal agenesis. NTDs are apparently etiologically heterogeneous.

Anencephaly and its Associated Malformations

“…Anencephaly, even though a defect of the neural tube can affect many other systems selectively [18]. The intake of 0.5mg of folic acid [19] during the course of pregnancy reduces the risk of anencephaly but does it have a similar effects on other anomalies is poorly understood.…”

Neural tube defects in Gauteng, South Africa: Recurrence risks and associated factors

“…[15][16][17] The widely accepted explanation for this finding is that many of these spontaneous abortions occur because the fetus is affected by an NTD or other congenital abnormality. It is believed that about half of pregnancies complicated by NTDs will end in spontaneous abortion.…”

“…[15][16][17] The increase in spontaneous abortions, despite the exclusion of pregnancies known to be affected by NTDs from the analysis, may be explained by the occurrence of NTDs or other congenital abnormalities in fetuses in which anomalies were present but not recognised, [15] or may suggest that a history of miscarriage is an independent risk factor for NTDs.…”

Neural Tube and Craniofacial Defects With Special Emphasis On Folate Pathway Genes

“…The superficially "brain-like" mass of exposed tissue typically consists of collagen and connective and vascular tissue covered by an epithelial membrane (Hunter, 1993). When the brain is completely absent, the defect is referred to as holo-anencephaly, which occurs in approximately 65% of failed anterior neural tube closure (Myrianthopoulos and Melnick, 1987). A more mild malformation, meroanencephaly, involves the protrusion of the cerebrovasculosa through a partially formed skull (Myrianthopoulos and Melnick, 1987).…”

“…When the brain is completely absent, the defect is referred to as holo-anencephaly, which occurs in approximately 65% of failed anterior neural tube closure (Myrianthopoulos and Melnick, 1987). A more mild malformation, meroanencephaly, involves the protrusion of the cerebrovasculosa through a partially formed skull (Myrianthopoulos and Melnick, 1987). According to Hunter (1993), approximately half of anencephalic infants are stillbirths, while the remainder live for variable periods of up to 48 hours.…”