Prevalence of Neural Tube Defects in the Province of Quebec, 1992
Wals, Philippe De, Trochet, Cecile, Pinsonneault, Linda, Canadian Journal of Public Health
A retrospective study of neural tube defects (NTDs) was carried out among elective terminations of pregnancies, stillbirths and live births to women residing in two regions of Quebec, in 1992. Primary data sources included the hospital administrative data system MEDECHO, stillborn and infant death certificates, and the list of patients seen at three spina bifida clinics. Hospital records were reviewed. A total of 30 NTD cases were identified. The prevalence rate was 1.41 per 1,000, indicating a threefold reduction in frequency during the last three decades. All 17 cranial defects but only 5 of 13 spinal defects were diagnosed during pregnancy. Elective terminations were performed at an average gestation of 18 weeks (range II to 21 weeks). The MEDECHO file allows a complete identification of NTD cases, but diagnostic categories are not very specific and coding errors are present.
Une etude retrospective des anomalies de fermeture du tube neural (AFTN) a ete realisee parmi les interruptions medicales de grossesse, les mortinaissances et les naissances vivantes de meres residant dans deux regions du Quebec, en 1992. Les sources d'information primaires ont Etd le systeme medicoadministratif MEDECHO, les certificats de mortinaissances et de decks infantiles, ainsi que la liste de patients suivis dans trois cliniques de spina bifida. Les dossiers hospitaliers ont ete consultes. Au total, 30 cas d'AFTN ont etc identifies. Le taux de prevalence est de 1,41 pour mille, ce qui indique une reduction par un facteur 3 durant les trois dernieres decennies. Les 17 cas de malformation cr"anienne ont ete detectes en debut de grossesse, mais seulement 5 des 13 cas de malformation de la colonne vertebrale. Les interruptions de grossesse ont etc pratiquoes en moyenne a 18 semaines de gestation (valeurs extremes: 11 et 21 semaines). Le fichier MEDECHO permet une identification complete des cas d'AFTN, mais les categories diagnostiques sont peu specifiques et il existe des erreurs de codification.
Neural tube defects (NTDs) constitute an important public health problem in terms of mortality, morbidity, social cost and human suffering.1 It is well established that increasing consumption of food folate or using folic acid supplements during the periconceptional period decreases the risk of affected pregnancy.2-8 In 1993, the Society of Obstetricians and Gynaecologists of Canada recommended that all women of childbearing potential should consider 0.4 mg folic acid supplementation or adequate dietary equivalent on a daily basis.9 In 1994, the Canadian Task Force on the Periodic Health Examination also recommended that women of childbearing age increase their consumption of folic acid to 0.4 mg/d.10 In the U.S., fortification of grain and cereal products at a level of 140 mg of folic acid /100 g of grain is mandatory, effective January 1st, 1998.11 Fortification at the same level is authorized in Canada. In Quebec, there is no systematic program for prenatal detection of NTDs using measurement of maternal serum a-fetoprotein level. Screening in low risk pregnancies relies on ultrasonographic examination, which is usually offered between 16 and 20 weeks of gestation.12 The effectiveness of these prevention strategies should be evaluated.
We performed a retrospective study in two regions of the province of Quebec, namely the Eastern Townships and Monteregie, in order to assess the prevalence of NTDs at birth, and to evaluate the impact of prenatal diagnosis and selective termination of affected pregnancies. We also wanted to estimate the validity of hospital discharge summary data currently used for epidemiologic surveillance in Canada. 13
The study population includes elective terminations for fetal malformations, stillbirths and live births, occurring in 1992, to women residing in the regions of the Eastern Townships and Monteregie (representing approximately 20% of the total population of the province of Quebec). …