Every so often a health headline lands that makes pregnant women anxious about something they’d been told to do. “Folic acid linked to childhood asthma” was one of those, and it sent plenty of mums-to-be second-guessing a supplement that is, in fact, one of the most important things they can take. So let’s set the record straight: the benefits of folic acid are large and well proven, the asthma scare was weak and hasn’t held up, and you should keep taking it. Here’s the fuller picture.
Folic acid before and in early pregnancy dramatically reduces the risk of serious birth defects of the baby’s brain and spine (neural tube defects). That benefit is well established. An old study raised a weak, uncertain signal about asthma from folic acid taken late in pregnancy, but it hasn’t been borne out, and no such concern applies to the early folic acid that matters most. Keep taking it as advised.
This is the rare case where the science is truly settled: take your folic acid.
Why folic acid matters so much
Folic acid is the manufactured form of folate, a B vitamin the body needs to build a baby’s neural tube, the early structure that becomes the brain and spinal cord. That structure forms in the first few weeks of pregnancy, often before a woman even knows she’s pregnant, and getting enough folate at that point sharply lowers the risk of neural tube defects such as spina bifida. This is why the advice is to start folic acid before conception if you can, and to keep taking it through the first trimester. It’s one of the clearest, best-evidenced pieces of pregnancy advice there is, backed by decades of research and every major health authority.
Where the asthma scare came from
The worry traced back to a study that looked at women taking folic acid in the later part of pregnancy, from around the 30th week, and checked their children for asthma at three and a half and five and a half years old. Even in that study, the picture was thin: it found no evidence that folic acid in early pregnancy caused any harm, and no link between the folate women got from food and asthma in their children. At most it raised a weak, uncertain question about supplements taken late in pregnancy, the period when folic acid matters least anyway.
Since then, larger and better research has not confirmed a meaningful link between folic acid and childhood asthma. In other words, a single, limited study produced an alarming headline that later evidence did not support, which is exactly the sort of thing that causes needless worry.
Weighing it up
Set the two things side by side. On one hand, a strong, repeatedly proven benefit: far fewer babies born with devastating defects of the brain and spine. On the other, a weak, unconfirmed and possibly non-existent signal about asthma, tied only to late-pregnancy supplements. There is no real contest. The protection folic acid gives in early pregnancy is enormous and certain; the asthma worry is neither. Health authorities continue to recommend folic acid precisely because the maths is this lopsided.
How to take it
- Start early. Ideally begin folic acid before you conceive, or as soon as you know you’re pregnant, and continue through at least the first trimester, as your doctor advises.
- Take the recommended dose. A standard dose is advised for most women, with a higher dose for those at greater risk (for example, with a family history of neural tube defects, diabetes, or on certain medications). Your doctor will tell you which applies to you.
- Eat folate-rich foods too, such as leafy greens, beans, lentils and oranges, though food alone rarely provides enough and that is why the supplement is advised.
- Don’t stop because of a scary headline. If a news story worries you, ask your doctor rather than quietly dropping a supplement that protects your baby.
Common questions
Does folic acid cause asthma in children?
There’s no good evidence that it does. An old, limited study raised a weak question about folic acid taken late in pregnancy, but larger research hasn’t confirmed a meaningful link, and no such concern applies to the early folic acid that matters most. Keep taking it.
Why is folic acid important in pregnancy?
It sharply reduces the risk of neural tube defects like spina bifida, which affect the baby’s developing brain and spine in the first few weeks. This benefit is strong and well proven and that is why it’s recommended before and in early pregnancy.
When should I take folic acid?
Ideally before you conceive, or as soon as you know you’re pregnant, and through at least the first trimester. Because the neural tube forms very early, starting before pregnancy is ideal.
How much folic acid should I take?
A standard dose for most women, and a higher dose if you’re at greater risk (such as a family history of neural tube defects, diabetes, or certain medications). Your doctor will advise the right dose for you.
Should I stop folic acid if I read a worrying study?
No. Talk to your doctor first. The proven benefit of folic acid is large and certain, and single alarming headlines often aren’t supported by later evidence. Don’t drop it on the strength of a scare.
The short version
Folic acid is one of the safest, most valuable things you can take before and during early pregnancy, because it protects your baby against serious defects of the brain and spine. The “folic acid and asthma” scare came from a single limited study, applied only to late-pregnancy supplements, and hasn’t stood up to better research. Keep taking your folic acid as advised, eat your greens alongside it, and take pregnancy health headlines to your doctor rather than to heart.
More on eating well in pregnancy
This is general information, not medical advice. Guidance is drawn from major health authorities including the UK NHS and US CDC. Take folic acid as advised by your doctor, who can set the right dose for you.