Vitamin D

What is it?

Vitamin D occurs in oily fish, cod liver oil, red meat, liver, egg yolks, and is added to foods such as margarine and breakfast cereal. Vitamin D is naturally produced in the body from sunlight on the skin. It is also present in some vitamin supplements. Vitamin D is needed for the body to absorb calcium and deficiency can lead to weak and soft bones (rickets).

Is it safe to take vitamin D in pregnancy?

In the UK it is recommended that pregnant women take a daily supplement containing 10 micrograms of vitamin D.

UK guidelines also suggest that pregnant women with a diagnosed vitamin D deficiency can be treated with high dose vitamin D under supervision by a doctor.

What if I have already taken vitamin D during pregnancy?

Vitamin D supplements (10 micrograms per day) are recommended in pregnancy. If you have taken higher dose vitamin D in pregnancy without medical supervision you should discuss this with your doctor or midwife. Additionally, if you are pregnant and have taken any medicines it is always a good idea to let your doctor know in case an adjustment of dose is required and/or you need any additional monitoring or treatment.

This leaflet summarises the scientific studies relating to the effects of vitamin D on a baby in the womb.

Can taking vitamin D in pregnancy cause my baby to be born with birth defects?

A baby’s body and most internal organs are formed during the first 12 weeks of pregnancy. It is mainly during this time that some medicines are known to cause birth defects.

There is no evidence that vitamin D supplements in early pregnancy are linked to birth defects in the baby. Small numbers of mothers receiving higher dose vitamin D have also not shown that this causes birth defects in the baby.

Can taking vitamin D in pregnancy cause miscarriage?

No studies have investigated the chance of miscarriage in women taking vitamin D in pregnancy.

Can taking vitamin D in pregnancy cause stillbirth?

A study of 540 pregnant women taking vitamin D supplements in pregnancy found that they did not have a higher chance of stillbirth compared to women not taking a vitamin D supplement.

Can taking vitamin D in pregnancy cause preterm birth or my baby to be small at birth (low birth weight)?

Studies of pregnant women taking vitamin D supplements in pregnancy found that they did not have a higher chance of preterm birth or of the baby having a low birth weight compared to women not taking a vitamin D supplement. However, one large study found that pregnant women taking supplements containing both vitamin D and calcium were slightly more likely to have a preterm delivery. It is unclear whether this might be because women taking calcium supplements in pregnancy may be doing so because of underlying health issues, which might themselves increase the chance of preterm birth. Further research is therefore required.

Can taking vitamin D in pregnancy cause learning or behavioural problems in the child?

No studies have investigated learning and development in children whose mothers took vitamin D supplements during pregnancy.

Will my baby need extra monitoring during pregnancy?

As part of their routine antenatal care most women will be offered a scan at around 20 weeks of pregnancy to look for birth defects and to check the baby’s growth.

Taking vitamin D in pregnancy is not expected to cause any problems that would require extra monitoring.

Are there any risks to my baby if the father has taken vitamin D?

We would not expect any increased risk to your baby if the father took vitamin D before or around the time you became pregnant.

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 healthcare provider. They can access more detailed medical and scientific information from www.uktis.org.