[Comparison of the epidemiological characteristics of neural tube defects classified according to failure of the different points of closure].

Objectives: To study the epidemiological characteristics of neural tube defects (NTD) classified according to the theory of multi-site closure of the neural tube and to correlate several factors with the failure of different closure sites.

Material and methods: We used the data from the Spanish Collaborative Study of Congenital Malformations (ECEMC), collected from April 1976 to April 1995. During this time, 757 NTD of non-syndromic origin were diagnosed. These were classified into groups according to the failure of the point of closure and a range of variables were analyzed by comparing the different groups of NTD with each other.

Results and conclusions: Among non-syndromic NTD, 2.11 % recurred in siblings. However, the real recurrence rate in our population is 2.63 %, which corresponds with the recurrence rate observed before 1986. From this year the recurrence rate was modified by the legal possibility of abortion after prenatal diagnosis. The infants with NTD classified according to multi-site closure failure of neural tube differed in weight, mortality, maternal use of valproic acid, and maternal diabetes mellitus. While valproic acid is more specific to failure of closure sites 1 and 1 5, maternal diabetes mellitus preferentially affects failure of closure site 4. Closure site 4 is clearly genetically determined: it is frequently observed in genetic syndromes, predominantly affects females and is associated with a higher rate of maternal abortions and higher recurrence. Moreover, it is frequently observed in infants with multiple congenital anomalies and is associated with a higher rate of malformations among relatives.