R. Goldbloom et al., PERIODIC HEALTH EXAMINATION, 1994 UPDATE .3. PRIMARY AND SECONDARY PREVENTION OF NEURAL-TUBE DEFECTS, CMAJ. Canadian Medical Association journal, 151(2), 1994, pp. 159-166
Objective: To make recommendations on nutritional interventions and sc
reening manoeuvres to prevent the birth of infants with neural tube de
fects (NTDs). Options: Folic acid consumption through diet or suppleme
ntation in women at low risk and at high risk of having a fetus with a
n NTD, and maternal serum alpha-fetoprotein (MSAFP) screening in low-r
isk pregnancies. Outcomes: A reduction in the incidence rate of NTDs a
nd potentially harmful effects of false-positive results of screening
tests (i.e., abortion of a normal fetus). Evidence: A MEDLINE search w
ith the use of medical subject headings ''neural tube defects,'' ''pre
natal diagnosis'' and ''prevention and control'' identified 103 origin
al articles published between January 1979 and March 1993. Two reviewe
rs extracted the data by applying the rules of evidence developed by t
he Canadian Task Force on the Periodic Health Examination. Values: The
task force's evidence-based methods and values were used; high value
was placed on prevention of NTDs and on limitation of the harmful effe
cts of a pregnancy involving a fetus with an NTD. Benefits, harms and
costs: Evidence suggests that folic acid supplementation can decrease
the incidence rate of NTDs in low-risk pregnancies by 40% to 60% with
no adverse effects. MSAFP screening between the 16th and 18th weeks of
gestation can reach a sensitivity of 83% and a specificity of 98% whe
n it is used as part of an organized program. The effect of screening
on the incidence rate of NTDs depends on whether affected fetuses are
aborted. Recommendations: All women of childbearing age should be advi
sed to increase their consumption of folic acid through diet or supple
mentation to 0.4 mg/d beginning 1 month before pregnancy and ending at
the start of the second trimester. MSAFP screening is recommended in
low-risk pregnancies only when it is part of a screening program that
includes access to all necessary diagnostic services. High-risk women
should be referred to genetic counselling before they plan a pregnancy
. Validation: These recommendations are comparable to the current reco
mmendations of the US Centers for Disease Control and Prevention, the
Society of Obstetricians and Gynaecologists of Canada, the Canadian La
boratory Centre for Disease Control and the Canadian College of Medica
l Geneticists, and they were validated though external review. Sponsor
: These guidelines were developed and endorsed by the Canadian task fo
rce, which is funded by Health Canada.