Academic journal article Bulletin of the World Health Organization

Prevention of Neural Tube Defects by the Fortification of Flour with Folic Acid: A Population-Based Retrospective Study in Brazil/Prevention Des Anomalies Du Tube Neural Par L'enrichissement En Acide Folique Des Farines: Etude Retrospective En Population Au Bresil/La Prevencion De Los Defectos del Tubo Neural Mediante El Enriquecimiento De la Harina Con Acido Folico: Un Estudio Poblacional Retrospectivo En Brasil

Academic journal article Bulletin of the World Health Organization

Prevention of Neural Tube Defects by the Fortification of Flour with Folic Acid: A Population-Based Retrospective Study in Brazil/Prevention Des Anomalies Du Tube Neural Par L'enrichissement En Acide Folique Des Farines: Etude Retrospective En Population Au Bresil/La Prevencion De Los Defectos del Tubo Neural Mediante El Enriquecimiento De la Harina Con Acido Folico: Un Estudio Poblacional Retrospectivo En Brasil

Article excerpt

Introduction

Neural tube defects, which are detected in about 300 000 neonates worldwide each year, are a major cause of neonatal morbidity and mortality. (1) They are caused by the abnormal closure of the embryonic neural tube between 22 and 28 days after conception. The resulting structural defects, which may occur anywhere along the neuraxis, often lead to the postpartum exposure of neural tissue and this, in turn, may lead to severe impairment in the child's physical and mental development. (2-3)

Classically, neural tube defects are divided into two main groups: defects affecting brain structures--such as anencephaly and encephalocele and defects that affect the structures of the spinal cord--such as meningocele, myelomeningocele and other forms of spina bifida. (4,3) Anencephaly--also called exencephaly or craniorachischisis--is defined as the complete or partial absence of the brain. This defect, which is caused by a failure of the cephalic neural tube to close, (6-7) leads to fetal deaths, stillbirths or neonatal deaths. In encephalocele, the brain and meninges herniate through a skull defect, especially in the occipital region. (1) Spina bifida is characterized by the failure of fusion of the vertebral arches of the spine. This defect can be covered by skin--when it is known as spina bifida occulta--or be associated with a cystic protrusion. In meningocele, this protrusion contains abnormal meninges and cerebrospinal fluid. In myelomeningocele, the cystic protrusion contains elements of the spinal cord and/or nerves.

Neural tube defects have been associated with both genetic factors--e.g. simple gene mutations and chromosomal abnormalities (7)--and maternal factors such as folate intake, age, ethnicity, obesity and the use of antiepileptic drugs. (8) If maternal intake of folic acid can be increased around the time of conception, the risk of the occurrence of neural tube defects may be reduced by 60-70%. (9-12) This preventive strategy has been adopted by 78 countries (13) that have mandated the addition of folic acid to flour. Such folic acid fortification has already been associated with reductions in the prevalence of neural tube defects in Canada, (14) Chile, (15) South Africa (16) and the United States of America (USA). (17)

In 2002, Brazils Health Surveillance Agency made the fortification of wheat and maize flour with iron and folic acid mandatory in the country from June 2004--allowing flour producers more than a year to adapt to the new legislation (18) All wheat and maize flour sold in Brazil since June 2004 should contain 0.15 mg folic acid per 100 g. (18)

Although most studies on the prevalence of neural tube defects have been focused on live births, the prevalence of such defects among miscarriages and stillbirths may be higher than that among live births. In the United Kingdom of Great Britain and Northern Ireland, for example, such defects were detected in 2.8/1000 live births and 5.3/1000 miscarriages at eight weeks of gestation. (19) In Northern Ireland and south-east England neural tube defects were 7.1/1000 in live births and 10.8 /1000 in eight-week miscarriages. (20)

In this population-based retrospective study, we aimed to determine if the mandatory addition of folic acid to flour sold in Brazil was associated with a change in the prevalence of neural tube defects in live and stillbirths.

Methods

Databases

We analysed data that had been routinely collected, in central, south-eastern and southern Brazil, by the national ministry of health and recorded within either the live birth information system database--i.e. as live births--or the mortality information system database --i.e. as stillbirths.

The live birth database was introduced in 1990 but has only included notification of congenital anomalies since 1999. Between 1999 and 2006, only one of the codes of the International classification of diseases and related health problems (21) (ICD) could be entered in this database per birth. …

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