Risk factors associated with neural tube defects

Spina bifida represents a broad category of neural tube defects (NTD) which affects approximately 1-4/1,000 live births. Since effective prenatal diagnostic testing for 90% of NTD is available through measurement of alpha-fetoprotein (AFP) in amniotic fluid, ascertainment of high risk factors associated with the occurrence of NTD would be both desirable and important. At the present time, generally, the major indication for prenatal testing for NTD is the presence of a first-degree relative with some form of NTD. To date, few other factors have been utilized to identify a family as 'at risk'. The authors have studied a group of 19 families of 10 female and 9 male index cases with NTD. The parents of each index case were interviewed and pedigrees were prepared on each family. Conditions screened for in these families included spina bifida and other NTD, pilonidal cysts, scoliosis, kyphosis and other vertebral disorders which were hypothesized to be possibly related to NTD. There were 58 first-, 171 second-, and 802 third-degree relatives screened in this study. This sample population was similarly characteristic with regard to sex, maternal age and birth order distributions as compared to previous populations of NTD described and was therefore considered to be representative. The results indicate that: (a) pilonidal cysts are 6 times more frequent in the fathers and twice as frequent in the mothers of children with spina bifida than in the general population; and (2) scoliosis is 5 times more frequent in both mothers and fathers of children with spina bifida than in the general population. These preliminary studies suggest that several minor clinical conditions in parents may be important to consider as possible risk signs suggesting couples be considered for prenatal evaluation for the prevention of NTD.