Vitamin D & The Risk of Miscarriages

Article by Rhiannon Lambert, BSc MSc RNutr

Trigger Warning: This blog discusses miscarriages

The latest research carried out by Tommy’s, a baby charity that funds pioneering research to help understand why, sadly, some pregnancies end in a loss, has found that a vitamin D deficiency is linked to an increased risk of miscarriages (a pregnancy loss before 23 weeks) or recurrent miscarriages (3 or more miscarriages in a row) in pregnant women.

Vitamin D, known as the sunshine vitamin, is created by our bodies when we are exposed to direct sunlight. It can also be found in small amounts in some foods such as oily fish like salmon, egg yolks, and fortified breakfast cereals.

“Research suggests that a vitamin D deficiency during pregnancy significantly increases the risk of miscarriage or recurrent miscarriage.”

— Dr Jennifer Tamblyn, Tommy's Charity Researcher

Why do we need vitamin D?

Our bodies need this vitamin to help us maintain healthy muscles, teeth, and bones, as well as to provide support for the immune system. The NHS recommends that that all adults in the UK supplement with 10µg of vitamin D in the winter months (October to April), and that some higher risk groups, including pregnant and breastfeeding women, should supplement all year round.

Why is vitamin D important during pregnancy?

An adequate vitamin D intake in pregnant women is essential for both the health and wellbeing of both the mother and baby. Epidemiological evidence, i.e. data from studies that examine the prevalence and distribution of medical conditions and disease, has revealed that many pregnant have sub-optimal vitamin D levels within their body. This may have negative implications during pregnancy, as data has suggested that a vitamin D deficiency may be linked to pre-eclampsia, gestational diabetes, bacterial vaginosis, and an increased risk for having a C-section delivery.

Experts have also found that vitamin D is essential for bone development in a growing foetus, as well as having an important role in early pregnancy in mother and baby immune responses and blood vessel development, both of which are needed in a healthy pregnancy.

Tommy’s Charity research: what did they find?

The most recent evidence, in a review lead by Tommy’s researchers, now also suggests that a vitamin D deficiency during pregnancy significantly increases the risk of miscarriage or recurrent miscarriage. Researchers found that vitamin D plays a role in maintaining a healthy placenta, the organ responsible for delivering oxygen and nutrients to foetus. In women with low vitamin D levels this negatively impacts the function of the placenta, which results in a miscarriage.

This evidence highlights the importance of pregnant women maintaining adequate vitamin D levels through either supplementation and/or dietary sources. The researchers behind this review also suggested the need for more research to be carried out to understand whether treatment of a vitamin D deficiency in women in the preconception period is needed to also protect against the risk of miscarriage.

Extra support

Miscarriages are unfortunately much more common than you may think, with the NHS estimating that 1 in 8 known pregnancies sadly end in a miscarriage. Many more miscarriages occur in women who don’t even know they are pregnant so this number may actually be even higher.

If you would like some further support then you may find these resources useful: