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Folic Acid
Home > Excite > Lesson 5: Folic
Acid Epidemiology Studies |
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Excite Education Curriculum Module:
Folic Acid
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Lesson 5: Folic Acid Epidemiology Studies
Estimated
Time: 20 minutes
Researchers have
found that the B-vitamin, folic acid, can prevent neural tube defects
like anencephaly and spina bifida. As a result, there is something
women can do to prevent many of these birth defects from happening in
the future.
A study
was done in Europe, and the results were published in 1991. Women
who had already had a baby with an NTD were given a pill to take before
their next pregnancy and during the first 3 months of pregnancy (first
trimester). One group was given extra folic acid. The second group
was given a pill without folic acid. None of the women or their
doctors knew which type of pill they were taking. Below is a table
of the results of the study.
Study
of women who had already had a baby with an NTD |
|
With
NTD |
Without
NTD |
Total |
Percent
with NTD |
Group
1
Folic Acid |
6 |
497 |
593 |
6
÷ 593 x 100 = 1% |
Group
2
No Folic Acid |
21 |
581 |
602 |
21
÷ 602 x 100 = 3.5% |
In
epidemiology, we calculate relative risk to show the
difference from one treatment to another. |
RELATIVE
RISK A comparison of the risk of disease in
one group with the risk of disease in another group. |
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Individual
Activity
Divide the risk of having a baby with an NTD without taking folic acid
into the risk of having a baby with an NTD when taking folic acid.
3.5% ÷ 1% = 3.5
The study found the
risk for having a baby with an NTD is 3.5 times higher if a woman did
not take folic acid. It appeared that folic acid protected women
from having another baby with an NTD.
As a result of the
study, the CDC made a statement in its August
2, 1991, Morbidity and Mortality Weekly Report (MMWR). The
MMWR is a weekly report of illnesses and deaths in the U. S.
published by CDC in Atlanta. This statement urges women who
already had a baby with an NTD and are planning to have another baby to
take 4 milligrams (mg) of folic acid. They should start taking 4
milligrams of folic acid before they get pregnant and during the first 3
months of pregnancy (first trimester).
Another research
study testing folic acid was published in 1992. This study focused
on women who had not had a baby with an NTD. All
of these women were given one of two pills to take before they were
pregnant and through the first trimester. One group took folic
acid with other vitamins (a multivitamin). The second group
received a different pill without folic acid. Once again, none of
the women knew what type of pill they were taking.
Study of women who had not had a baby with an NTD before
|
|
With
NTD |
Without
NTD |
Total |
Percent
with NTD |
Group
1
Folic Acid |
0 |
2,104 |
2,104 |
0
÷ 2104 x 100 = 0% |
Group
2
No folic Acid |
6 |
2046 |
2052 |
6
÷ 2052 x 100 = 0.3% |
None of the women who took folic acid in a multivitamin had a baby with
an NTD. Three out of 1000 women (0.3%) who did not take folic acid
had a baby with an NTD. Thus, NTD risk was greater in the group
that didn't take folic acid.
Individual
Activity
Calculate
and interpret the relative risk for this example. A
study in the U. S. followed women who had never had a baby with an NTD.
Women who took a pill with folic acid before pregnancy and during the
first trimester were compared with women who did not take vitamin pills
during this time.
Study of women who had not had a baby with an NTD before
|
|
With
NTD |
Without
NTD |
Total |
Percent
with NTD |
Group
1
Folic Acid |
10 |
10,703 |
10,713 |
10
÷ 10713 x 100 = 0.093% |
Group
2
No folic Acid |
39 |
11,905 |
11,944 |
39
÷ 11944 x 100 = 0.325% |
Find the relative risk for NTDs in women who did not take folic acid:
0.325 ÷ 0.093
= about 3.49 times greater risk of having a baby with an NTD
As a
result of this study, the U. S. Public Health Service announced
on September 11, 1992, that all women who could possibly get
pregnant should take 0.4 milligram of folic acid every day.
Milligrams,
Micrograms, and the Metric System
1 Gram = 1,000
milligrams = 1,000,000 micrograms. A gram is about the weight (but
not the size) of two raisins, so a microgram is a very, very small
amount. Because we need only a small amount of folic acid, it is
called a micronutrient. Still, folic acid is very important every
day because the body has to have it for healthy blood and cells and to
make DNA.
The word microgram
can also be shown as mcg or µg. The Greek symbol µ means micro
and is pronounced mu. The word milligram can be shown as mg.
Both milligrams and micrograms are used to describe the amount of folic
acid in food.
The U. S. Public
Health Service recommends that all women who can become pregnant take 0.4
mg of folic acid. The recommendation also states that women who
have already had a baby with an NTD and want to have
another baby should take 4 milligrams of folic acid daily.
Individual
Activity
Part
1
Find
the amount of micrograms (mcg) equal to 4 milligrams
(mg) of folic acid.
Hint: 1 mg = 1000 mcg.
1 mg
= 4 mg
1000 mcg.
? mcg
How many micrograms
of folic acid do women who have already had a baby with an NTD need to
reduce the chance of having another baby with an NTD? (Answer:
4000 micrograms)
Part
2
The
U. S. Public Health Service announced in 1992, that all women
who could get pregnant should take 0.4 milligram of
folic acid every day. Using the metric system, convert 0.4
milligram (mg) into micrograms (mcg or µg). Hint:
1 mg = 1000 mcg.
1 mg
= 0.4 mg
1000 mcg
? mcg
How many micrograms
(mcg) of folic acid do women who have not had a baby with an NTD need a
day? (Answer: 400 mcg)
Group
Discussion
Who
needs to take more folic acid: women who have already had a baby
with an NTD or women who have not had a baby with an NTD? How much
more folic acid do they need? Why do you think they need more?
Women who have
already had a baby with an NTD and want to have another baby should take
more folic acid. If they have already had one baby with an NTD,
they are more likely to have another with the birth defect.
Therefore, they need to take 10 times as much, 4000 mcg folic acid
instead of 400 mcg. People who take more than 1000 mcg of folic
acid should only take it under the care of a doctor.
Link
to Lesson 6: Folic Acid Information
Date: September 6, 2006
Content source: National Center on Birth Defects and Developmental
Disabilities
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