Vitamin D in pregnancy: why it matters and how much you need
Vitamin D is one of a small number of nutrients the NHS specifically recommends as a supplement throughout pregnancy. It plays a central role in how the body uses calcium and phosphate, the minerals most important for forming and maintaining strong bones and teeth. During pregnancy, the developing baby relies entirely on the mother's vitamin D status, making adequate levels more important than at almost any other time in life. Despite this, deficiency is common in the UK, partly because the main source of vitamin D is not food but sunlight, which is limited for much of the year.
What vitamin D does during pregnancy
Vitamin D supports the regulation of calcium and phosphate in the body. These two minerals are the primary building blocks of the skeleton, and during pregnancy the baby's skeletal development draws on the mother's supply. Vitamin D helps the gut to absorb calcium from food, and without adequate vitamin D even a calcium-rich diet cannot be used efficiently. This is why vitamin D and calcium work together: one without the other leaves a gap in the system.
Beyond bone health, vitamin D plays a role in immune function and muscle function, though the evidence in these areas continues to develop. The Scientific Advisory Committee on Nutrition (SACN), the expert body that advises the UK government on nutrition, reviewed the evidence comprehensively in its 2016 report on vitamin D and health. SACN concluded that musculoskeletal health is the area where the evidence for the importance of adequate vitamin D is strongest, and it is this evidence base that underpins current NHS recommendations.
The consequences of severe vitamin D deficiency during pregnancy can include rickets in the newborn, a condition in which the bones are soft and fail to harden properly. Milder deficiency is associated with lower bone mineral density in the baby, though the long-term effects of borderline deficiency are an active area of research. The key practical point is that the NHS recommends a daily supplement throughout pregnancy precisely because the consequences of deficiency are significant and the supplement is safe and inexpensive.
Why deficiency is so common in the UK
Unlike most vitamins, the body produces vitamin D internally when skin is exposed to ultraviolet B (UVB) rays from the sun. Food sources exist but are limited. This means that in countries like the UK, where sunshine is unreliable for much of the year and many people spend most of their time indoors, inadequate vitamin D status is widespread across the population, not just in pregnant people.
The angle of the sun in the UK between October and March means that UVB rays do not reach the earth's surface with enough intensity for the skin to make vitamin D. This six-month period is why the NHS recommends that everyone in the UK, pregnant or not, takes a daily vitamin D supplement in autumn and winter. For pregnant people, the recommendation extends year-round, because the baby's needs are continuous and because sunlight exposure alone cannot be relied upon even in summer.
Certain groups face additional barriers to making vitamin D from sunlight. People with darker skin tones have higher levels of melanin, which reduces the efficiency of vitamin D production in response to UVB exposure. People who spend little time outdoors, whether because of their lifestyle, their work, or their mobility, have less opportunity for sun exposure. People who cover most of their skin for religious or cultural reasons are similarly at increased risk. Those who are obese may also have lower circulating vitamin D levels, as vitamin D is fat-soluble and can be sequestered in fatty tissue rather than available for use.
The NHS recommendation: 10 micrograms per day
The NHS recommends that all pregnant and breastfeeding women take a supplement containing 10 micrograms (400 IU) of vitamin D every day. This is consistent with the SACN recommendation and applies throughout pregnancy from the first trimester onwards, not just in winter. The advice is also to continue through breastfeeding, because breast milk is a poor source of vitamin D and the baby continues to depend on the mother's vitamin D status after birth.
In practice, the 10 microgram dose is widely available. It is included in most pregnancy multivitamins, and it is also the amount contained in the Healthy Start vitamins provided free to qualifying pregnant people in England through the NHS Healthy Start scheme. If you are not sure whether your current pregnancy supplement contains the right amount, check the label for vitamin D content expressed in micrograms or IU: 10 micrograms and 400 IU are equivalent.
If your GP suspects or has confirmed that you have a vitamin D deficiency on the basis of a blood test, they may recommend a higher therapeutic dose. This is separate from the standard pregnancy supplementation advice and will be managed as part of your antenatal care. You should not increase your dose beyond 10 micrograms per day without medical guidance.
Food sources and their limits
While it is difficult to meet vitamin D requirements from food alone, it is still worth knowing which foods contribute meaningfully. Oily fish, including salmon, mackerel, sardines and fresh tuna, are the richest food sources. Eggs (specifically the yolk) contain a modest amount. Some foods are fortified with vitamin D in the UK, including most margarines and some breakfast cereals and plant-based milk alternatives, though the amounts vary by brand and product.
The practical limitation of food sources is scale. Even regular consumption of oily fish and fortified foods is unlikely to provide 10 micrograms of vitamin D per day in a reliable or consistent way. Oily fish also carries the separate advisory limit of no more than two portions per week during pregnancy, due to pollutant levels. This is not a reason to avoid oily fish, which is a valuable source of omega-3 fatty acids, but it is a reason not to rely on fish as the primary strategy for meeting vitamin D needs. A daily supplement is a far more dependable approach.
Safety and upper limits
Vitamin D is fat-soluble, which means the body stores it in fatty tissue rather than excreting any excess in urine the way it does with water-soluble vitamins. This means that very high doses taken over time can build up to levels that cause harm. The NHS advises that taking more than 100 micrograms (4,000 IU) per day should be avoided during pregnancy, as it may be harmful to the baby.
The recommended pregnancy dose of 10 micrograms per day is a long way below this upper limit, so there is no safety concern with following standard advice. If you are taking a pregnancy multivitamin alongside a separate vitamin D supplement, check the combined total does not exceed safe levels. Most pregnancy supplements contain 10 micrograms or less, but checking is a simple precaution. If you are uncertain, ask your midwife or pharmacist to review what you are taking.
Frequently asked questions
How much vitamin D should I take in pregnancy?
The NHS recommends 10 micrograms (400 IU) of vitamin D per day throughout pregnancy and breastfeeding. This is the recommendation from the Scientific Advisory Committee on Nutrition (SACN). Some GP practices may recommend higher doses for those with confirmed deficiency.
Who is most at risk of vitamin D deficiency in pregnancy?
People at higher risk include those who spend little time outdoors, those who cover their skin for religious or cultural reasons, those with darker skin tones (who produce less vitamin D from sunlight), and those who are obese. People in these groups are particularly encouraged to take a daily supplement.
Can I get enough vitamin D from food alone?
It is very difficult to get enough vitamin D from food alone. The main sources are oily fish, eggs and fortified foods. Sunlight on the skin is the main natural source. The NHS recommends everyone in the UK (pregnant or not) takes a vitamin D supplement in autumn and winter.
Is vitamin D safe to take in pregnancy?
Yes. The NHS-recommended dose of 10 micrograms per day is safe in pregnancy. Very high doses (above 100 micrograms per day) should be avoided. Vitamin D is fat-soluble, so excess builds up in the body, but the recommended pregnancy dose is well within safe limits.
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