Folic acid: learn why this nutrient is essential during your pregnancy

Folates are crucial for your baby's development

Taking folic acid supplements before getting pregnant (preconception stage) is very important and they should be taken daily. Taking folates, together with adequate vitamin supplements throughout pregnancy, reduces the chances of neural tube defects (NTD) and other cardiac, urinary and orofacial malformations (such as cleft lip) in babies.

Folate-deficient pregnant women

La embarazada debe tomar folatos y suplementos de ácido fólico

Although we tend to use the terms folic acid and folate interchangeably, it is important to differentiate the two of them: folate is a water-soluble B vitamin (B9) that occurs naturally in foods such as liver, green leafy vegetables, oranges and legumes, whereas folic acid is the synthetic form of folate found in supplements and added to fortified foods.

Mammals, as well as other animals, do not have the capacity to synthesise folates, so we must obtain them from our diet. However, the daily intake of folates is generally lower than the amounts recommended by health authorities for pregnant women, so an external supply of these nutrients must be taken in the form of vitamin supplements.

Folic acid: pregnant women should take 400 micrograms a day 

The recommended intake level of folic acid during pregnancy according to the Spanish Society of Obstetrics and Gynaecology (SEGO) is 400 micrograms a day for single pregnancies.

If you are pregnant with twins, you should take 1,000 micrograms (1 mg) a day during the three trimesters of your pregnancy.

Folic acid should be taken at least one month before conception and at least during the first three months of pregnancy to reduce the risk of neural tube defects (such as the widely-known spina bifida) in at least 50-70% of cases.

But it is important to remember that taking folic acid does not prevent all neural tube defects: some are not related to folic acid deficit but to chromosomal alterations or to poorly controlled diabetes mellitus before pregnancy.

What if I have had a previous NTD-affected pregnancy

Embarazada con déficit de ácido fólico y suplementos vitamínicos

In Spain, the General Directorate of Public Health of the Ministry of Health and Consumer Affairs offers the following recommendations to pregnant women:

  •  A woman who has not had a pregnancy affected by a neural tube defect (or NTD) before and who is planning to become pregnant should take 0.4 mg (400 micrograms) of folic acid per day for single pregnancies.

  • Women who have had a previous pregnancy affected by a neural tube defect should take 4 mg/day of folic acid.

  • In both cases, folic acid supplements must be taken at least one month before pregnancy and at the very least during the first three months of pregnancy. A diet rich in folate- containing foods should also be followed.

Pregnant with twins: how much folic acid should you take?

As we explained before, in twin pregnancies the recommended doses of folic acid are a little higher than for single pregnancies. The recommended dose of folic acid is 0.6 mg/day (600 micrograms/day) before pregnancy and then 1 mg/day (1,000 micrograms/day) during the whole pregnancy. By doing so, the needs of the growing foetuses and placentas are met.

The risk factors requiring an increase in folate dose from 0.4 to 4 mg per day are:

  • A previous pregnancy that was affected by a neural tube defect
  • Treatment with anticonvulsants such as valproic acid or carbamazepine
  • Maternal obesity, BMI greater than 30 Kg/m2
  • Insulin-dependent pregestational diabetes

Tomar ácido fólico en embarazos gemelares

Very important: folic acid before pregnancy

Embarazada prepara su embarazo con ácido fólico

Patients who have been treated with assisted reproduction techniques will have been taking folic acid since before they became pregnant. However, in a spontaneous pregnancy, it is usually less frequent for women to have been taking folic acid beforehand, and they usually start taking it as soon as they find out they are pregnant.

However, it is very important to take folic acid before conception and on a daily basis, as there is no significant reduction in the risk of neural tube defects when the supplement is taken irregularly or from the second month of pregnancy.

Folate intake, together with multivitamin complexes throughout pregnancy (provided they do not contain fat-soluble vitamins above the recommended daily doses), reduces the incidence not only of neural tube defects but also of cardiac, urinary, orofacial (cleft lip, for example) and limb malformations, and pyloric stenosis.

Check out these folate-rich foods

Fortunately, our Mediterranean diet is rich in high-folate foods. Try to always have them at hand in the kitchen:  




Cereals supplemented with folic acid

½ cup: 300


100 gr: 185

Cooked spinach

½ cup: 100

Baked beans

½ cup: 90

Cooked asparagus

4 pieces: 85

White rice

½ cup: 65

Raw spinach

1 cup: 60

Cooked green peas

½ cup: 50

Cooked broccoli

½ cup: 45


½ cup: 45


1 cup: 40


½ cup: 40

Tomato juice

180 ml: 35


Dr María de la Calle Fernández-Miranda
Head of the Obstetric Medicine and High-Risk Obstetrics Unit. Department of Obstetrics and Gynaecology, La Paz Hospital (Madrid).