Vitamin D Deficiency in Pregnancy

• 4 October 2018, by SANUSq Research team
• 10 min reading time

Vitamin D deficiency is strikingly common in pregnancy — and it's a stage of life when getting it right matters for two.

Written by SANUSq Research Team | Medically reviewed by Dr Ajay Kumar, MD
Published: 6 February 2020 | Updated: 24 August 2026

A common shortfall at an important time

Pregnancy places extra demands on the body, and vitamin D is one nutrient where many women fall short. Global surveys consistently find high rates of vitamin D deficiency among pregnant women, across many countries and climates. Because vitamin D supports the developing baby's bone formation as well as the mother's own health, this is a shortfall worth understanding — and it's a topic to approach carefully, since pregnancy is not the time for guesswork.

Why the requirement matters more now

Vitamin D is unusual among nutrients in that most of it doesn't come from food at all. It is made in the skin from UVB sunlight, then converted by the liver and kidneys into the active hormone that governs how much calcium the gut absorbs. Because it is fat-soluble, the body stores it, which is why status tends to drift down slowly over a winter rather than changing day to day.

Pregnancy adds a second person to that system. A developing baby cannot make vitamin D, so its supply comes across the placenta from the mother, and the level a baby is born with broadly tracks hers. At the same time the demand for calcium rises sharply in the later part of pregnancy, when the baby's skeleton is being mineralised, and it is vitamin D that makes dietary calcium available for that job. So the requirement is not simply higher in a vague sense; there is a specific reason it matters at a specific time, and a shortfall in the mother is a shortfall for both.

Reading the evidence honestly

Those associations are consistent, but it's important not to overstate them. Association studies show that deficiency travels alongside higher risk; they don't by themselves prove that correcting it prevents these outcomes, and results from supplementation trials have been mixed. What's well established is that vitamin D is important in pregnancy and that deficiency is common — which is why many health authorities recommend that pregnant women ensure an adequate intake and that those at higher risk have their levels checked.

Most vitamin D pregnancy research is observational, and that shapes what it can tell us. Women who are low in vitamin D often differ from those who aren't in other ways too — time spent outdoors, diet, body weight, general health, how early they came under care — and those differences can influence the same outcomes being measured. Good studies adjust for what they can measure, but they cannot adjust for everything. This is why a sensible reader treats a consistent association as a reason to take the nutrient seriously, and not as a promise that topping it up changes the outcome.

Who is more likely to run low

Deficiency is common enough that nobody should assume they are exempt, but some circumstances make it more likely, and knowing which apply to you is useful information to bring to an appointment. Skin that produces more melanin needs considerably more UVB exposure to make the same amount of vitamin D, so women with darker skin tones living at higher latitudes are consistently found to have lower levels. So are women who cover most of their skin for cultural or religious reasons, and anyone who spends most of daylight hours indoors, whether through shift work, illness or simply the shape of the working day.

Season and latitude matter a great deal. Through the winter months at northern latitudes the sunlight is too weak at the relevant wavelength for the skin to make vitamin D at all, so what the body has is what it stored or ate. A pregnancy that runs mostly through autumn and winter therefore sits in a different position from one that runs through a summer. Carrying more body weight is also associated with lower blood levels, as vitamin D is taken up into fat tissue. Conditions affecting fat absorption — coeliac disease, Crohn's disease, previous bariatric surgery — reduce uptake from food, and a diet with little oily fish, egg or fortified food offers less to absorb. Closely spaced pregnancies and carrying twins add to the demand.

None of this is a diagnosis. Vitamin D status is measured with a blood test, not estimated from a list, and whether that test is warranted is a clinical judgement.

On dosage — a word of caution

People often want a specific number, but the right amount of vitamin D in pregnancy is genuinely individual, and official recommendations vary between countries. This really is a decision to make with your prenatal care provider, who can check your level if needed and advise what's appropriate for you. Pregnancy is exactly the situation where personalised medical guidance beats a one-size-fits-all figure from an article. For context on why deficiency is so widespread, especially in the darker months, see how to get enough vitamin D in winter.

What to raise at your antenatal appointment

The most useful thing this article can do is help you have a better conversation with your midwife, GP or obstetrician, because that is where the actual decision belongs. Antenatal appointments are busy, so it helps to arrive with the question already formed rather than hoping it comes up.

Worth asking: what the guidance where you live says about vitamin D in pregnancy, since national recommendations genuinely differ; whether anything in your circumstances — skin tone, how much sun you get, the season your pregnancy falls in, your weight, a gut condition, a previous pregnancy where deficiency was found — makes a blood test worth doing; and if a supplement is advised, what form and what amount are right for you specifically.

Bring everything you already take, including the pregnancy multivitamin, and show the labels rather than describing them from memory. Many prenatal preparations already contain vitamin D, and it is easy to end up taking it twice over without realising. This is also the moment to ask what to avoid: several national guidelines advise against cod liver oil and other supplements high in retinol during pregnancy, because of the vitamin A they contain rather than the vitamin D. And because vitamin D is fat-soluble and stored rather than flushed out, more is not straightforwardly better — another reason the amount is a clinical decision rather than a personal experiment.

Frequently asked questions

Why is vitamin D important in pregnancy?

Vitamin D supports the baby's developing bones and the mother's health, and deficiency has been associated with higher risks of complications such as pre-eclampsia and gestational diabetes. It's an important nutrient at this stage of life.

Is there a standard pregnancy vitamin D dosage?

There's no single right number — recommendations vary by country and by individual need. This is a decision to make with your midwife, GP or obstetrician, who can check your level and advise what's appropriate for you. Please don't take a figure from an article, including this one, as a substitute for that.

Is vitamin D deficiency common in pregnancy?

Yes, very. Global surveys find high rates of deficiency among pregnant women across many regions and climates, which is why the topic gets so much attention.

Can I get enough vitamin D from the sun while pregnant?

Sun exposure helps, but it depends heavily on season, latitude, skin tone and sun-safety practices, so it's unreliable on its own — particularly in winter. Diet and, where advised, supplementation are more dependable.

Which foods provide vitamin D?

Oily fish, egg yolks and fortified foods are the main dietary sources. They help, though many people need more than diet alone provides, especially in pregnancy.

Can you take too much vitamin D in pregnancy?

Vitamin D is fat-soluble and stored in the body rather than cleared quickly, so excess intake is possible and more is not automatically better. That is one of the reasons the amount is a decision for the clinician looking after your pregnancy, and not something to work out for yourself.

Should I ask for a vitamin D blood test?

It's a reasonable question to raise, particularly if several of the circumstances above apply to you. Whether testing is offered varies between countries and services, so ask your midwife or doctor rather than assuming either way.

Does a pregnancy multivitamin already contain vitamin D?

Many do, in varying amounts. Take the labels of everything you're using to your appointment so the whole picture can be looked at together, rather than adding one supplement on top of another.

References

1. Wei SQ, Qi HP, Luo ZC, et al. Maternal vitamin D status and adverse pregnancy outcomes: a systematic review and meta-analysis. J Matern Fetal Neonatal Med. 2013;26(9):889–99. PMID 23311886

Read more on the blog

• Vitamin D in pregnancy and childhood asthma
• How to get enough vitamin D in winter
• Vitamin D: the natural antibiotic

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Explore more on our channel, @SANUSqHealthSupplements.

We wish you good health on your terms.
The team at SANUSq.

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Absorption & Dosage Hormones & Fertility Vitamin D

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