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Folic Acid and the Prevention of
Neural Tube Defects (NTDs)
Challenges and Recommendations for Public Health
Heidi S. Reisch, RD1
Mary A.T. Flynn, PhD, RD, RPH Nutr2
ABSTRACT
Objective: To outline specific challenges facing public health in Canada that need to be
addressed to ensure that all women of childbearing years can attain optimal folate status
for prevention of NTDs.
Methods: The new Dietary Reference Intake (DRI) for folate was examined in terms of the
literature on the effective form of the vitamin, the level of folic acid provided by the
Canadian food supply and the folic acid content of available supplements.
Findings: There are six major challenges facing public health in Canada on this issue.
These include confusion among health professionals and the general public on the
effective form of the vitamin, requirements, and the necessity of taking supplements.
Further obstacles to ensuring optimal folate status in all women of childbearing age in
Canada include the limited amounts of folic acid that are currently permitted in foods and
the difficulties involved in identifying the amount of folic acid provided in these foods in
relation to needs.
Interpretation: These challenges must be addressed to enable women in Canada to make
an informed choice about folic acid. This has the potential to prevent up to 70% of the
300 births affected by NTDs each year.
La traduction du résumé se trouve à la fin de l’article.
Health Promotion & Disease Prevention, Healthy Communities, Calgary Health Region
1. Nutrition Specialist
2. Coordinator, Nutrition & Active Living
Correspondence and reprint requests: Mary A.T. Flynn, P.O. Box 4016, Station “C”, Calgary, AB T2T
5T1, Tel: 403-943-8123, Fax: 403-943-8132, E-mail: [email protected]
254 REVUE CANADIENNE DE SANTÉ PUBLIQUE
I
n Canada, approximately 300 (or 1 of
every 1000) births are affected by
Neural Tube Defects (NTDs) each
year, with spina bifida being the most
common NTD.1 Direct health care costs
for children with spina bifida could be up
to $1.7 million per year. These costs do
not account for the physical and emotional
tolls upon the families affected nor do they
reflect the lost economic potential associated with NTDs. While prenatal screening
for NTDs can be performed with reasonable accuracy and reliability, no treatment
is available in utero for the correction of
NTDs. One of the most important medical breakthroughs in recent times was the
discovery that taking a simple B vitamin,
folic acid, in the peri-conceptual period
could protect as many as 70% of babies
affected by neural tube defects.2-4 Given
the limitations of prenatal screening, primary prevention of NTDs is an issue of
tremendous importance. However, by the
time most women realize that they are
pregnant, the period where folic acid is
protective will have passed because the
neural tube closes within 3 to 4 weeks after
conception. Therefore, one of the greatest
challenges for public health is to ensure
that all women of childbearing years have
optimal folate status for prevention of
NTDs. This paper outlines the specific
challenges facing Public Health in Canada.
Challenge 1: Health professionals and
the public do not fully understand
that it is folic acid, the synthetic form
of the B vitamin, rather than the
folate found naturally in foods that
plays a role in the prevention of
NTDs.
Scientific evidence has demonstrated that a
maternal red blood cell folate level of
>400 ng/mL, at the time of conception, is
optimal in reducing risk of NTDs developing in the fetus. 5 This optimal level is
much greater than the cut-off level used to
determine folate deficiency leading to
megaloblastic anemia (red cell folate ≤ 140
ng/mL.)6 It has been demonstrated that
the optimal level of folate status can only
be achieved through the consumption of
0.4 mg of the synthetic form of the vitamin
(folic acid) and not through the consumption of foods naturally rich in folate.6-9 This
is because folic acid is much more stable
and bioavailable than its natural form,
folate.
VOLUME 93, NO. 4
CHALLENGES FOR PREVENTION OF NTDs USING FOLIC ACID
In 1998, Canada and the United States
harmonized nutrition recommendations,
and introduced a special recommendation
that all women of childbearing age consume 0.4 mg/day of synthetic folic acid
from fortified foods or vitamin supplements (see Table I) in addition to natural
food folate to help prevent NTDs.6
Challenge 2: All women need to be
aware of their specific folic acid
requirements for occurrence and
recurrence of NTDs.
Factors that put women at much higher
risk of having a pregnancy affected by
NTDs include having had a previously
affected pregnancy (i.e., a high risk of
recurrence), having a family history of
NTDs, poor maternal health, diabetes,
treatment with anticonvulsant drugs, medically diagnosed obesity and overconsumption of alcohol. Women affected
by these factors require larger doses of folic
acid than the recommended daily
0.4 mg.6,11 The daily requirement for these
women is commonly estimated as 1.0 - 4.0
mg of folic acid but the exact dose needs to
be medically recommended. Due to the
uncertainty of the effects of these higher
doses (see Table IV, Challenge 6 below) it
is recommended that vitamin B12 status
be monitored and that the higher dose be
discontinued at 8 weeks gestation, after the
neural tube has closed.6
Challenge 3: The complex differences
between folic acid, folate and DFEs
need to be simplified with folic acid
being clearly identified as the effective form of the vitamin for the prevention of NTDs.
The special recommendation of a folic acid
intake of 0.4 mg/day, to prevent NTDs, is
targeted specifically for women in the
childbearing age range. However, for all
individuals over the age of 14 years, the
Recommended Daily Allowance (RDA) for
folate is estimated to be 0.4 mg of Dietary
Folate Equivalents (DFEs) with pregnant
and lactating women having slightly higher
RDAs (see Table I). DFEs represent a measure of estimated bioavailability considering
the profound differences that exist between
folic acid and folate.7,12,13 DFEs are a very
useful tool for assessing overall dietary
intakes of folates and folic acid in the ongoing quest for assessing the effective dose
JULY – AUGUST 2002
TABLE I
Dietary Reference Intakes (Recommended Dietary Allowances (RDAs)*, Special
Recommendations, Upper Limits (UL)†, and Estimated Dietary Intakes of Folate and
Folic Acid for Women6,10
Recommended Dietary Intakes
Age (years)
Special
RDA
Recommendation‡ (DFE mg/
Folic Acid
day)§
(mg/day)
14-18
0.4
0.4
Pre-menopausal 19-50+ 0.4
0.4
Postmenopausal
–
0.4
Pregnancy 14-18
0.4
0.6
Pregnancy 19+
0.4
0.6
Lactation 14-18
0.4
0.5
Lactation 19+
0.4
0.5
Estimated Dietary Intakes
UL
Folic Acid
(mg/day)
0.8
1.0
1.0
0.8
1.0
0.8
1.0
Estimated
Estimated
Folate from
Folic Acid
Diet (mg/day)|| from Diet¶
(mg/day)
0.274
0.08 – 0.1
0.257
0.08 – 0.1
0.241
0.08 – 0.1
–
0.08 – 0.1
–
0.08 – 0.1
–
0.08 – 0.1
–
0.08 – 0.1
* RDA (Recommended Dietary Allowance) – the average daily dietary intake level that meets the
nutrient requirement of nearly all (97 to 98 percent) healthy individuals in particular life stages
and gender group
† UL (The tolerable upper intake level) = upper safe level of intake of folic acid from fortified foods
and/or supplements
‡ Special Recommendation – that all women of childbearing age consume 0.4 mg per day of synthetic folic acid from fortified foods or vitamin supplements in addition to natural food folate to
help prevent NTDs.
§ DFE (Dietary Folate Equivalents) = naturally occurring food folate (µg) + [1.7 X of synthetic folic
acid (µg)]8
|| Weighted mean nutrient intake, Food Habits of Canadians, data provided between August 1997April 19989
¶ From fortified flour-based products
TABLE II
Level of Folic Acid Fortification of Permitted Foods in Canada and the US, and the
Amount of Folic Acid Delivered in Serving Sizes14,15
US
Folic Acid Content
per Serving
Food Product
Serving Size
White* flour
White* bread
Enriched pasta
(i.e., macaroni,
spaghetti), noodles, rice
(white)
Ready-to-eat cold cereal
100 g
25-30 g (1 slice)
0.14
0.02
(35-40 g dry pasta)
equivalent to 140 g
(1 cup cooked)
0.06 – 0.09
30 g (1 cup to ½ cup puffed
to dense cereal)
0.1 – 0.4
Canada
Folic Acid
Content per
Serving (mg)
0.15
0.02 – 0.03
0.095 – 0.11
0.018 – 0.025
*Note: Whole-grain products do not have to be enriched.
for prevention of occurrence and recurrence
of NTDs. However, the validity of the
DFE measure is an ongoing research issue.
Therefore there are very complex differences between folic acid, folates and the
DFE measure, with folic acid being the
only effective form of the vitamin in relation to prevention of NTDs.7,9 The problem is that health professionals use these
terms interchangeably, and are not clear on
the ultimate importance of ensuring 0.4 mg
of folic acid (or more for women at greater
risk) for the prevention of NTDs. As an
example, even the authors, who are registered dietitians working in public health,
did not fully understand that naturally
occurring folates in foods, measured as mg
of folate or DFEs, do not provide optimal
protection against NTDs.
Challenge 4: Currently women can
meet only 25% of their folic acid
requirements through the Canadian
food supply.
As of November 1998, fortification of
flour and selected grains with folic acid
became mandatory in both Canada and
the US.14,15 This is estimated to increase
the daily intake of folic acid among women
18-34 years of age by 0.08 - 0.1 mg, representing 25% of women’s special folic acid
needs (see Table II). The benefits from fortification are expected to reduce the number of NTD-affected pregnancies by 6 to
31%. Optimal fortification providing
0.4 mg of folic acid per day could reduce
the number of NTD-affected pregnancies
by up to 70% without causing any associated adverse effects.
CANADIAN JOURNAL OF PUBLIC HEALTH 255
CHALLENGES FOR PREVENTION OF NTDs USING FOLIC ACID
TABLE III
Vitamin and Mineral Supplements: Random Survey of 5 Leading Pharmacies from
Outlets in Calgary: Folic Acid Content, Vitamins and Minerals Above RDA and UL for
Women of Childbearing Age and Cost for 30 Days Including all Women of Childbearing
Age
Folic Acid
Vitamin and/or
Vitamin and/or
Content Range
Mineral Above RDA Mineral Above
(mg/daily dose)
and Below UL
UL (% above UL)
Multivitamins and Minerals
Regular Strength
0.1 – 0.4
Vitamin B1, B2, B6, B12,
Niacin*
and D-pantothenic acid,
(13-25%)
Biotin, Vitamin A, C, D
Women Specific
0.4
Vitamin B1, B2, B6, B12,
niacin and D-pantothenic
acid, Zinc, Vitamin A, D
High Potency
0.4 – 1.0
Vitamin B1, B2, B6, B12,
Niacin*
and/or Stress Tabs
and D-pantothenic acid,
(13-40%)
Zinc, Vitamin D
B-complex
1.0
Vitamin B1, B2, B6, B12,
niacin and D-pantothenic
acid
Prenatal vitamin
0.8 – 1.0
Vitamin B1, B2, B6, B12,
supplements
niacin and D-pantothenic
acid,Vitamin C, D, Zinc,
Copper, Manganese
Folic Acid
0.4 – 1.0
Cost per
30 Days
($)
~ 3.00
~ 2.50
~ 5.00 – 8.00
~2.80
~ 4.20
~ 0.95
* Case reports and clinical trials have reported flushing effects of oral doses of 30 to 1000 mg
niacin/day within 30 minutes to 6 weeks of the initial dose (40 - 100 mg of niacin were found in
the multivitamin and mineral supplements). Individuals with hepatic dysfunction or a history of
liver disease, diabetes mellitus, active peptic ulcer disease, gout, cardiac arrhythmia, inflammatory bowel disease, migraine headaches, and alcoholism are distinctly susceptible to the adverse
effects of excess niacin intake. Therefore, people with these conditions may not be protected by
the UL for niacin for the general population.6
In Canada, folic acid may be added to
ready-to-eat breakfast cereals up to a maximum of 0.06 mg/100g, which provides
0.02 - 0.03 mg of folic acid per 30 g serving size (~5% of women’s special needs).
The United States permit fortification of
breakfast cereals in amounts that provide
from 0.1 mg of folic acid up to 0.4 mg per
30 g serving size (25 to 100% of women’s
special needs – see Table II). In Europe,
voluntary fortification permits the addition
of folic acid to foods other than grains,
such as dairy products. In the United
Kingdom, in addition to the wider range
of foods that may have folic acid added,
mandatory fortification of flour, at double
the level currently added to Canadian
flour, has been proposed. This fortification
is estimated to increase folic acid intake by
0.2 mg per day, reducing NTD risk by
approximately 42%,9 which represents an
11 to 36% greater decrease in risk than can
be achieved through Canada’s current fortification program.
Due to the limited range of foods that
may be fortified and the restrictions on the
amounts of folic acid that may be added to
these foods, Canadian women cannot meet
the special recommendation (0.4 mg folic
acid/day) through diet.
256 REVUE CANADIENNE DE SANTÉ PUBLIQUE
Challenge 5: Currently it is difficult
for women to identify foods fortified
with folic acid and to determine the
amount provided in relation to their
needs.
The new mandatory nutrition labelling
gives Canadians the control to make judicious food choices to optimize their health.
However, in relation to folic acid, the initial
period of labelling in Canada will not allow
easy identification of foods fortified with
folic acid or make it simple for women to
determine the amount provided in relation
to their special needs. This is because the
reference amount of folic acid indicated on
the label will initially be based on the 1983
nutrient recommendations, which represent
slightly over half the special recommendation of 0.4 mg and do not distinguish
between folate and folic acid. The new
labelling makes it mandatory to report the
content of 13 nutrients considered to be
important for public health on labelled
foods. Despite its public health significance,
folic acid is not included as one of these crucial nutrients. In addition, the units (milligrams, mg) that will be used on labels to
express the folic acid content in foods will
compel women to calculate intake using
decimal points rather than whole numbers
(i.e., amounts that add up to 0.4 mg).
Challenge 6: The only effective way
that Canadian women can use folic
acid to protect their babies from
NTDs necessitates taking a daily vitamin supplement that is not readily
available (in optimal nutrient doses)
and represents an ongoing cost ($11 $35 per year) to them throughout
their childbearing years.
In Canada, health professionals have no
option but to promote the use of a daily
supplement containing folic acid for prevention of NTDs (see above). A random
survey of five leading Calgary pharmacy
outlets found that the supplements available provide folic acid (expressed in mg) in
varying amounts. These supplements
include multivitamin/mineral, and prenatal
specific supplement formulations, and single folic acid vitamin supplements (see
Table III). Regular strength multivitamin/mineral formulations provide between
0.1 - 0.4 mg of folic acid per tablet (i.e.,
between 25 - 100% of women’s special
needs). With the exception of regular multivitamin/mineral supplements, the majority of the supplements available were found
to provide more than double the daily
amount of folic acid recommended (see
Table III). In addition, some of these supplements were found to provide more than
the daily tolerable upper level intake (UL)
for another vitamin, niacin. The long-term
safety of this is unknown (see Table III).
There are limited data on the safety of consuming folic acid doses over the UL
(1.0 mg) and it is recommended that
women consume no more than this.6 Large
amounts of folic acid (between 1 and
5 mg/day) have been found to mask vitamin B12 deficiency by correcting the early
symptom of megaloblastic anemia.
Untreated vitamin B12 deficiency results in
irreversible neurological damage. 6
Therefore long-term excessive supplemental
folic acid intake has the potential to
increase the prevalence of compromised
neurological function in groups at risk of
Vitamin B12 deficiency (e.g., vegans).
Resulting neurological damage may be serious, irreversible and crippling. It is a matter
of concern that with the fortification of
Canadian flour (providing ~ 0.1 mg/day)
and the majority of available folic acid supplements containing a 1 mg daily dose,
many Canadian women will exceed the UL
for folic acid, risking potential long-term
VOLUME 93, NO. 4
CHALLENGES FOR PREVENTION OF NTDs USING FOLIC ACID
TABLE IV
Folic Acid and the Prevention of Neural Tube Defects (NTDs): Challenges and Possible Solutions for Public Health
Challenges
The effective agent that prevents NTDs is the synthetic form of the B vitamin folate (folic acid) because of its superior bioavailability.
Challenge 1: Health professionals and the public do not fully understand that it is folic acid, the synthetic form of the B vitamin, rather
than the folate found naturally in foods that plays a role in prevention
of NTDs.
Possible Solutions
A national Public Health campaign should be considered. This should
focus on educating health professionals and the public on the specific
importance of folic acid in the prevention of NTDs.
To help prevent the occurrence of NTDs, there is a special recommendation that all women capable of becoming pregnant consume 0.4 mg
of folic acid daily in the form of supplements and/or fortified foods, in
addition to consuming food folate from a varied diet. Women who have
had a baby affected by an NTD or who are at increased risk (see text)
need to seek medical advice because their folic acid requirements are
much higher (ranging from 1.0 – 4.0 mg/day).
Optimal maternal folate levels throughout a women’s childbearing
years are critical as the neural tube closes before most women even
know they are pregnant.
Challenge 2: All women need to be aware of their specific folic acid
requirements for occurrence and recurrence of NTDs.
All Canadian women capable of becoming pregnant need to know the
importance of taking folic acid daily;
- Women who have had a baby affected by an NTD or who are otherwise at increased risk (see text) need to be aware that they have special requirements for folic acid and need to seek medical advice.
- Women taking higher than recommended doses of folic acid need to
be regularly monitored by their physicians.
Currently, folates, folic acid and DFEs are used interchangeably, by
health professionals and the public, with little understanding of the profound differences in their effectiveness and relation to NTD prevention.
Challenge 3: The complex differences between folic acid, folate and
DFEs need to be simplified, with folic acid being clearly identified as
the effective form of the vitamin for the prevention of NTDs.
For successful prevention of NTDs, the differences between folic acid,
folate, and DFEs need to be clearly understood:
- Folic acid available in supplements and fortified foods protects against
the development of NTDs.
- Folate found naturally in foods protects against deficiency but does
not provide women with optimal folate status for NTD prevention.
- DFEs are a very useful tool for assessing overall dietary intakes of
folates and folic acid in the ongoing quest for assessing the effective
dose for prevention of occurrence and recurrence of NTDs. However,
until nutrition research fully evaluates the effectiveness of the DFE
measure, its use should be limited to research.
It is mandatory in Canada to fortify white flour with folic acid so that
100 g of flour provides 0.15 mg of folic acid. However, this fortification
is estimated to meet only 25% of the special recommendation of folic
acid (0.4 mg/day).
In addition to flour, only a few selected grains are permitted to be fortified with only very limited amounts of folic acid.
Challenge 4: Currently, women can only meet 25% of their folic acid
requirements through the Canadian food supply.
Food legislation could be modified to increase:
- the range of foods that can be fortified with folic acid, and
- the amount of folic acid added to fortified foods.
New labelling in Canada proposes:
- to use half the recommended daily intake for folate as a reference in
the initial introduction phase,
- to exclude folic acid from the 13 nutrients mandated to be included in
the nutrition label box, and
- to express the amount of folic acid present in milligrams, which compels women to calculate intakes using decimal points.
A time lag of 2 - 6 years for implementation of new labelling delays
NTD prevention strategies using folic acid in foods.
Challenge 5: Currently, it is difficult for women to identify foods fortified with folic acid and to determine the amount provided in relation to
their needs.
The identification of foods fortified with folic acid should be effortless
and the amount of folic acid they provide should be easily understood
by everyone.
- The most current recommendations (DRIs) should be used as reference intakes against which women can estimate their folic acid
intake.
- Foods fortified with folic acid should be clearly identified – attaching
a separate sticker in addition to the food label could be considered.
- Consideration should be given to making nutrition labelling on folic
acid mandatory – perhaps by including folic acid as the 14th nutrient
to be included in the proposed nutrition labelling box.
- The amount of folic acid could be expressed in micrograms instead of
milligrams to make it easier for women to calculate their overall
intake.
- Consideration should be given to initiating interim labelling for folic
acid-fortified foods immediately.
Supplements represent the only effective way for Canadian women to
meet their folic acid requirements for the prevention of NTDs. However,
readily available supplements containing folic acid:
- often provide above-optimal levels of folic acid or other nutrients,
- express the amount of folic acid present in milligrams (mg), which
compels women to calculate intakes using decimal points, and
- represent an ongoing cost to women of childbearing age.
Health professionals are often unaware of risks associated with taking
above-optimal dosages of folic acid in the long term.
Challenge 6: The only effective way that Canadian women can use folic
acid to protect their babies from NTDs necessitates taking a daily vitamin supplement that is not readily available (in optimal nutrient doses)
and represents an ongoing cost ($11 - $35 per year) to them throughout their childbearing years.
Control access to supplements:
- supplements that provide folic acid and other nutrients at optimal,
rather than above-optimal levels, should be readily available.
- those containing more than RDA for folic acid or other nutrients
should be available by prescription only.
Educate health professionals (especially pharmacists and physicians) on
the risks associated with taking folic acid and other nutrients above their
tolerable upper intake level.
health effects. None of the pharmacists
approached in the random survey of
Calgary outlets expressed any concerns in
JULY – AUGUST 2002
Promote clear and simple messages
- the amount of folic acid should be expressed in micrograms instead of
mg to make it easier for women to calculate their overall intake.
Address the cost issue:
- consideration could be given to making folic acid supplements available free of charge for all women of childbearing age.
recommending 1.0 mg folic acid/day and
were unaware that single folic acid supplements came in the form of a 0.4 mg dose.
Encouraging folic acid supplementation
throughout a woman’s entire childbearing
years (n = 25 years) represents a cost to
CANADIAN JOURNAL OF PUBLIC HEALTH 257
CHALLENGES FOR PREVENTION OF NTDs USING FOLIC ACID
women of $285 - $865 (at today’s prices).
This cost is insignificant in comparison to
the costs of raising a child with a neural tube
defect. Women from socio-economically
disadvantaged backgrounds are at higher
risk of having a pregnancy affected by
NTDs.1,16,17 It is unlikely that these women
would able to afford the extra long-term
cost of daily folic acid supplements, even if
they were aware of their particular importance.
Finally, studies have shown that it is difficult to persuade women at any income
level to comply with taking a daily supplement for years on end. Those who are
motivated to take a folic acid supplement
often take it too late, and this partly due to
the fact that 50% of pregnancies are
unplanned.
3.
4.
5.
6.
7.
8.
9.
CONCLUSION
The tremendous discovery of the protective effects of folic acid supplementation
raises many challenges for public health in
Canada. These must be overcome before
Canada can fully benefit by preventing up
to 70% of the 300 births affected by
NTDs each year. The point of this paper is
to highlight the issues that need to be clarified so that women can make an informed
choice about folic acid. Possible solutions
to overcome these challenges are outlined
in Table IV.
REFERENCES
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Wald NJ, Law M, Jordan R. Folic acid food fortification to prevent NTDs. Lancet
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Daly LE, Kirke PN, Molloy A, Weir DG, Scott
JM. Folate levels and NTDs - Implications for
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Cuskelly GJ, McNulty H, Scott JM. Effect of
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Cuskelly GJ, McNulty H, Scott JM. Fortification
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Laurence KM, James N, Miller M, Campbell H.
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Received: July 30, 2001
Accepted: March 7, 2002
RÉSUMÉ
Objectif : Décrire les défis particuliers que doit relever la santé publique au Canada pour que
toutes les femmes en âge de procréer aient un niveau de folate optimal pour la prévention des
anomalies du tube neural (ATN).
Méthode : Nous avons examiné le nouvel Apport nutritionnel de référence (ANREF) pour le folate à
la lumière de la documentation sur les formes efficaces de la vitamine, du niveau d’acide folique
dans l’alimentation canadienne et du contenu en acide folique des suppléments nutritifs
disponibles.
Constatations : Les responsables de la santé publique au Canada ont six grands défis à relever dans
ce dossier, notamment la confusion, parmi les professionnels de la santé et dans le grand public,
sur la forme la plus efficace de cette vitamine, sur les besoins en folate et sur la nécessité ou non de
prendre des suppléments. Les autres obstacles à surmonter sont les faibles quantités d’acide folique
actuellement autorisées dans les aliments et la difficulté de déterminer la quantité d’acide folique
dans l’alimentation par rapport aux besoins.
Interprétation : Il faut se pencher sur ces questions pour permettre aux Canadiennes de faire un
choix éclairé au sujet de l’acide folique. On pourrait éventuellement prévenir jusqu’à 70 % des
ATN, qui touchent 300 naissances chaque année.
VOLUME 93, NO. 4