Spina bifida before and after folic acid fortification in Canada.
BACKGROUND
In 1998, fortification of a large variety of cereal products with folic acid became mandatory in Canada. A multicentric study was carried out to assess the impact of this policy on the frequency of NTDs. The present analysis focused on spina bifida.


METHODS
The study population included approximately 2 million livebirths, stillbirths, and terminations of pregnancies because of fetal anomalies among women residing in seven Canadian provinces, from 1993 to 2002. Spina bifida cases were divided according to the upper limit of the defect: upper (cranial, cervical, or thoracic) and lower (lumbar or sacral) defects. Based on published results of red blood cell folate tests, the study period was divided into prefortification, partial fortification, and full fortification periods.


RESULTS
A total of 1,286 spina bifida cases were identified: 51% livebirths, 3% stillbirths, and 46% terminations. Prevalence decreased from 0.86/1,000 in the prefortification to 0.40 in the full fortification period, while the proportion of upper defects decreased from 32% to 13%. Following fortification, regional variations in the prevalence and distribution of sites almost disappeared.


CONCLUSIONS
Results confirmed the etiologic heterogeneity of spina bifida and the more pronounced effect of folic acid in decreasing the risk of the more severe clinical presentations.
De Wals
Philippe
P
Department of Social and Preventive Medicine, Laval University, Quebec City, QC, Canada. Philippe.Dewals@msp.ulaval.ca
Tairou
Fassiatou
F
Van Allen
Margot I
MI
Lowry
R Brian
RB
Evans
Jane A
JA
Van den Hof
Michiel C
MC
Crowley
Marian
M
Uh
Soo-Hong
SH
Zimmer
Pamela
P
Sibbald
Barbara
B
Fernandez
Bridget
B
Lee
Nora S
NS
Niyonsenga
Theophile
T
D002170:Canada / Q000453:epidemiology; D005260:Female; D005492:Folic Acid / Q000008:administration & dosage* / Q000502:physiology*; D005527:Food, Fortified; D006801:Humans; D008297:Male; D011247:Pregnancy; D015995:Prevalence; D012189:Retrospective Studies; D016135:Spinal Dysraphism / Q000453:epidemiology* / Q000378:metabolism / Q000517:prevention & control
D005492:Folic Acid