[Clinical epidemiological study of neural tube defects classified according to the five sites of closure].
OBJECTIVE
To identify the frequency at birth of neural tube defects (NTD) in the Spanish population. NTDs were considered as a whole as well as according to the different sites of closure failure, following the theory of multisite closure of the neural tube. To analyze the epidemiological characteristics of the different sites.


METHODS
Data derived from the Spanish Collaborative Study of Congenital Malformations (ECEMC), from April 1976 to March 1995. Among the 1,222,698 live births during this period, 784 infants had NTD were controlled. Among these, 784 infants had NTD.


RESULTS
The prevalence of NTD in our population was 1.01 per 1,000 births, a frequency which is considered medium-to low. Only 5.74% of the NTD were of known etiology: 2.17% were genic, 1.27% were chromosomic and 2.29% were environmental. Excluding NTD of genetic etiology, whether genic or chromosomic, most of the remaining were isolated defects (multifactorial) and 16.78% multiple malformations. Site 1, where the closure of the neural tube starts, represented 24% of all the affected sites. However, more than 50% of the NTDs corresponded to closure failure at the junction of two sites.


CONCLUSIONS
As in other populations with a low prevalence of NTD at birth, the prevalence of these defects in our population showed a trend to decrease with time, due to the possibility of interrupting gestation after prenatal diagnosis. All the NTD could be classified according to the theory of multisite closure of the neural tube, including 13 cases with several noncontiguous affected sites. Two types of NTD were observed: in the first, closure failed to occur and in the second, two closures failed to meet.
Sanchis Calvo
A
A
Servicio de Pediatría. Hospital Universitario Dr. Peset. Valencia, Spain. mcsanchis@digitel.es
Martínez- Frías
M
M
D000757:Anencephaly / Q000453:epidemiology; D003430:Cross-Sectional Studies; D006801:Humans; D007231:Infant, Newborn; D009436:Neural Tube Defects / Q000145:classification / Q000453:epidemiology*; D013030:Spain / Q000453:epidemiology; D016135:Spinal Dysraphism / Q000453:epidemiology