Folic acid

What is it?

Folic acid is a dietary supplement that is converted to folate (vitamin B9) in the body. Folate is essential for the production of blood cells and DNA. 

Why do I need to take folic acid during pregnancy?

Women require up to 10 times more folate during pregnancy to support the development of the baby. Low folate levels in the mother have been strongly linked to defects of the baby’s brain, skull, and spinal cord, known as ‘neural tube defects’, and possibly to some other birth defects, including cleft lip or palate. It is therefore recommended that all pregnant women, and those planning a pregnancy, take a folic acid supplement until at least the 12th week of pregnancy.

How much folic acid is recommended during pregnancy?

Most pregnancy folic acid supplements and multivitamins contain at least 400 micrograms of folic acid in each tablet. This is the recommended daily dose for most women who are likely to have normal folate levels.

Some women may have low folate levels because of a medicine that they are taking or because of their health. For example, certain epilepsy medicines, and being diabetic or obese, have been linked to low folate levels. In these situations pregnant women, or those considering a pregnancy, are advised to take a higher daily dose of 5 milligrams folic acid. High dose folic acid tablets need to be prescribed by a doctor. This higher dose is also advised for women who have previously conceived or given birth to a child with a neural tube defect, or have a family history of neural tube defects, or certain other birth defects (see below).

There are no known harmful effects on the development of the baby from taking 400 micrograms or 5 milligrams of folic acid daily during pregnancy.

How do we know that taking folic acid during pregnancy prevents birth defects?

A baby’s body and most internal organs are formed during the first 12 weeks of pregnancy. Many studies have shown that folic acid is very important for this to happen normally. 

Neural tube defects
There is excellent evidence from many large scientific studies that neural tube defects can be caused by low folate levels. Neural tube defects affecting the spine include spina bifida, which can range in severity from a harmless dimple in the skin of the lower spine, to openings in the spinal skin, muscle, bone, and nerves that can cause paralysis and incontinence. Neural tube defects affecting the skull bones and brain usually cause stillbirth or the baby to die shortly after birth and are often detected by antenatal scan.

Because the baby’s neural tube starts forming in the first four weeks of pregnancy (before the first missed period) it is best to start taking folic acid before trying to become pregnant, or as soon as a pregnancy is suspected if it has not been planned. In the UK and Ireland in the 1980s, before it was recommended that pregnant women take a folic acid supplement, about one in every 200 pregnancies resulted in a baby with a neural tube defect. Taking folic acid in early pregnancy reduces this risk to less than one in every 400. Taking folic acid before and during pregnancy is particularly important for women who have previously conceived or given birth to a baby with a neural tube defect.

There is not yet any scientific evidence to show whether higher dose folic acid (5 milligrams) is any better than the standard dose (400 micrograms) at reducing the chance of neural tube defects in babies of women with low folate levels due to, for example, obesity, diabetes, or being on certain medicines. It is also not known whether the neural tube defects that have been linked to taking medicines like sodium valproate can be prevented by taking folic acid. However, until more scientific information is available, high dose folic acid is advised in pregnant women who are at risk of having low folate levels or who are taking certain medicines.

Cleft lip and palate
Some studies have suggested that taking folic acid during early pregnancy may decrease the risk of cleft lip and/or palate in the baby, but other studies have not shown this effect. It is possible that only some types of cleft lip and/or palate are linked to low folate levels. More research on this subject is required.

Defects of the urinary system
One study has shown that babies of women who took folic acid supplements were less likely to have a birth defect of the urinary system (bladder, kidneys) than babies of women who didn’t. Further research is required to prove this.

Does taking folic acid during pregnancy affect my risk of miscarriage, stillbirth, preterm birth, or having a low birth weight baby?

Although some studies suggest that these pregnancy problems are less likely to occur in women who take folic acid supplementation, most studies have shown no difference in the rates of these pregnancy outcomes between women taking folic acid during pregnancy and those not taking folic acid. There is no scientific proof of any harmful effects of folic acid on the fetus.

Is there any evidence that taking folic acid during pregnancy protects against learning and behavioural problems in the child?

A baby’s brain continues to develop right up until the end of pregnancy. It is therefore possible that taking certain medicines at any stage of pregnancy could have a lasting effect on a child’s learning or behaviour.

One study found no difference in learning and behaviour of children whose mothers took folic acid supplements during pregnancy and children whose mothers didn’t. However, another study showed that children whose mothers took folic acid during pregnancy were about half as likely to develop autism compared to children who were not exposed to folic acid while in the womb.

It should, however, be noted that it is very difficult to study any effect of taking a medicine during pregnancy on the learning and development of the child and much more research is required before we can say whether or not taking folic acid during pregnancy protects a baby against learning and behavioural problems.

Will my baby need extra monitoring if I haven’t taken folic acid?

Most women will be offered a scan at around 20 weeks of pregnancy to look for birth defects as part of their routine antenatal care. Not taking folic acid during pregnancy would not normally require extra monitoring of your baby. However, if you are thought to be at high risk of folate deficiency, or have a family history of neural tube defects, your doctor may advise a more detailed ultrasound scan or further tests.

Methylfolate - what is it, and should I take it instead of folic acid?

Methylfolate is related to folic acid but is already ‘active’ and, unlike folic acid, does not rely on a gene called MTHFR to be converted to folate in the body. There have therefore been claims on some websites that methylfolate might be superior to folic acid as a means of preventing birth defects in the baby. Those making these claims have suggested that many people unknowingly carry a mutation or ‘spelling error’ in their MTHFR gene and may therefore not be able to convert folic acid effectively to folate. They have therefore suggested that taking methylfolate in pregnancy may be better.

However, whereas the benefits of taking folic acid before and during pregnancy have been clearly demonstrated, there are not yet any studies to confirm that taking methylfolate helps to prevent birth defects. It is also not known if talking methylfolate in pregnancy may have other unexpected effects on a baby in the womb, or in the mother. Specialist national guidelines in the USA that were updated in 2017 advise that all pregnant women, or women planning a pregnancy, including those that have MTHFR gene mutations, should take the standard recommended dose of folic acid unless a higher (5mg daily) dose of folic acid has been specifically recommended (see above). There may, however, be certain situations in which methylfolate use in pregnancy is suggested by a medical specialist. It is advisable to seek your doctor or midwife’s advice first if you are considering methylfolate supplementation during pregnancy, or if you have been diagnosed with a metabolic disorder which is known to affect the body’s ability to convert folic acid to folate.

Who can I talk to if I have questions?

If you have any questions regarding the information in this leaflet please discuss them with your health care provider. They can access more detailed medical and scientific information from www.uktis.org.