Publication: Porcentaje de la recurrencia de los defectos del tubo neural (DTN) y sus frecuencias en España: Evolución temporal de las mismas y su posibles causas
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2002-10
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Instituto de Salud Carlos III (ISCIII). Instituto de Investigación de Enfermedades Raras (IIER)
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Abstract
We analysed the birth prevalence of the different types of neural tube defects (NTD) in Spain in four periods of time, as well as their recurrence in our population and their variation along the time and causes. We have used data from the Spanish Collaborative Study of Congenital Malformations (ECEMC), with a total population of 1,703,322 births surveyed since 1980 till June 2001. After excluding those cases with syndromes of any etiology, and those with two different types of NTD, or the presence of discordant NTD in different sibs, a total of 937 infants with NTD were available for the present study. Birth prevalence of all forms of NTD show diminishing trends since 1985, when the law allowing voluntary interruption of gestations (VIG) with congenital defects was passed in Spain (Table 1, and Graph 1). The tendency is more marked for anencephaly and encephalocele than for spina bifida (Table 2). The recurrence (measured as pre–ocurrence) has also decreased with time, being 3.33% for NTD (Table 3) in the basal period (1980–1985), and 3.14% for anencephaly, 5.71% for encephalocele, and 2.31% for spina bifida. However, since the year 1985, the recurrence of anencephaly and encephalocele was cero, while for spina bifida (Table 4) decreases in 99.77% in the following period (1986–1992), and 100% in the other two consecutive studied periods. We also analysed the proportion ofmothers of cases and controls who received folic acid supplementation at least during the first trimester of pregnancy. Although we started asking for pre–conceptional intake of folic acid since 1998, the question was included in the questionnaires in the year 2001. Based on those data, only 2 mothers of cases and 3 of controls, used the folic acid before the current pregnancy. It is difficult to determine whether the decreases of the birth prevalence and recurrence figures are due to the impact of VIG or, in some degree, due to the periconceptional supplementation with folic acid. However, we consider that the group of mothers who have had a previous affected pregnancy, should constitute the group of population with a more adequate ingestion of folic acid. Nevertheless, the dramatic decrease of the recurrence in our population must be in part due to a secondary prevention produced by the VIG (which does not avoid the alteration of prenatal development) and, in part, to the primary prevention (which prevents the alteration of prenatal development) produced by the folic acid supplementation. In fact, the frequency of spina bifida, decreases “only” in a 56.95% in the last study period of time (Table 2), while its recurrence decreased in a 100%. We consider that there is no reason for not prescribing the adequate doses of folic acid to all women planning pregnancy, or not informing women at childbearing age about the convenience of starting supplementation before getting pregnant. However, to be sure that the prevention reach to thewhole population, includingmarginal groups, and those 50 and older, the Health Authorities of our country, should consider, as soon as possible, the necessity to fortify a generally used food like the flour. To paraphrase Oakley [2002], the opportunity to implement inexpensive passive population intervention to prevent severe human diseases come rarely, and fortification of flour is one of those rare opportunities.
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Epidemiología y Teratología: resultados de estudios sobre los datos del ECEMC
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Boletín del ECEMC: Rev Dismor Epidemiol 2002; V (nº 1): 36-42