No evidence that vitamin D protects against high blood pressure in pregnancy

June 20, 2018, British Medical Journal
Credit: CC0 Public Domain

There is no strong evidence that vitamin D protects against pregnancy-induced high blood pressure (hypertension) or pre-eclampsia, conclude researchers in The BMJ today.

The findings support current World Health Organization guidance that evidence recommending vitamin D supplements for during pregnancy to reduce adverse pregnancy outcomes is insufficient. However, in many countries, including the UK and the US, are advised to take a daily dose of vitamin D.

It is common for pregnant women to have low levels of vitamin D, which can suppress the hormone that regulates which may increase the risk of both and pre-eclampsia during pregnancy.

Previous population-based studies have found that women with lower levels of vitamin D are at greater risk of pre-eclampsia and some trials of vitamin D supplementation in pregnancy suggest a potential benefit. But it remains unclear whether vitamin D is a cause of pre-eclampsia.

So an international team led by Maria Magnus at the University of Bristol, set out to investigate whether vitamin D has a effect on or pre-eclampsia.

Using a technique called Mendelian randomisation, they examined whether genetic variants associated with vitamin D production and metabolism also influenced the risk of pregnancy-induced hypertension and pre-eclampsia for 7,389 women (751 with gestational hypertension and 135 with pre-eclampsia) from two large European studies (Avon Longitudinal Study of Parents and Children, also known as Children of the 90s, and Generation R Study).

They also performed another (two sample) Mendelian randomisation analysis of 3,388 pre-eclampsia cases and 6,059 controls.

Analysing genetic information as proxies for the exposure of interest in this way avoids some of the problems that afflict traditional observational studies, making the results less prone to unmeasured (confounding) factors. An association that is observed using Mendelian randomisation therefore strengthens the inference of a causal relationship.

Mendelian randomisation analysis showed no evidence to support a direct (causal) effect of vitamin D levels on risk of gestational hypertension or pre-eclampsia.

The researchers point to some study limitations. For example, the analyses were restricted to pregnant women. If vitamin D affects fertility, this may have resulted in selection bias.

In light of the uncertainty, they suggest further studies with a larger number of women with preeclampsia or more genetic variants that would increase the predictive power of vitamin D levels are needed.

"In combination with adequately powered clinical trials, this could help finally establish whether D status has a role in related hypertensive disorders." they conclude.

Explore further: Insufficient vitamin D linked to miscarriage among women with prior pregnancy loss

More information: Vitamin D and risk of pregnancy related hypertensive disorders: mendelian randomisation study, www.bmj.com/content/361/bmj.k2167

Related Stories

Insufficient vitamin D linked to miscarriage among women with prior pregnancy loss

May 30, 2018
Among women planning to conceive after a pregnancy loss, those who had sufficient levels of vitamin D were more likely to become pregnant and have a live birth, compared to women with insufficient levels of the vitamin, according ...

Eclampsia tied to increased relative risk of seizure disorder

November 10, 2017
(HealthDay)—The relative risk of a seizure disorder after eclampsia is higher than that of women unaffected by eclampsia but remains extremely low, according to a study published online Nov. 7 in Obstetrics & Gynecology.

Early onset of pregnancy complication may raise heart risks

September 15, 2017
(HealthDay)—Women who develop pre-eclampsia earlier in pregnancy may be at increased risk for heart problems soon after giving birth, a new study finds.

Genetic study suggests causal link between vitamin D deficiency and hypertension

June 26, 2014
New genetic research provides compelling evidence that low levels of vitamin D have a causal role in the development of high blood pressure (hypertension). The findings, published in The Lancet Diabetes & Endocrinology, suggest ...

Hypertensive disorders during pregnancy increase risk for high blood pressure after delivery

January 28, 2016
Women who are diagnosed with hypertensive disorders while pregnant are more than twice as likely to develop high blood pressure in the first year after delivery as women who did not have any pregnancy-related hypertension, ...

Insufficient evidence to guide recommendations on vitamin D in pregnancy

November 29, 2017
There is currently insufficient evidence to guide recommendations on the use of vitamin D supplements in pregnancy, conclude researchers in The BMJ today.

Recommended for you

1 in 9 U.S. adults over 45 reports memory problems

July 13, 2018
(HealthDay)—If you're middle-aged and you think you're losing your memory, you're not alone, a new U.S. government report shows.

Antioxidant benefits of sleep

July 12, 2018
Understanding sleep has become increasingly important in modern society, where chronic loss of sleep has become rampant and pervasive. As evidence mounts for a correlation between lack of sleep and negative health effects, ...

Footwear habits influence child and adolescent motor skill development

July 11, 2018
New research finds that children and adolescents who spend most of their time barefoot develop motor skills differently from those who habitually wear shoes. Published in Frontiers in Pediatrics, this is the first study to ...

How a Mediterranean diet could reduce osteoporosis

July 11, 2018
Eating a Mediterranean-type diet could reduce bone loss in people with osteoporosis—according to new research from the University of East Anglia.

Extreme heat and reduced cognitive performance in adults in non-air-conditioned buildings

July 10, 2018
Students who lived in dormitories without air conditioning (AC) during a heat wave performed worse on a series of cognitive tests compared with students who lived in air-conditioned dorms, according to new research led by ...

Suppressing negative emotions during health scare may whip up spiral of fear

July 10, 2018
Trying to suppress worries during a health scare, like the recent Zika outbreak, may lead to an ever-intensifying cycle of emotional suppression and fear, according to a team of researchers.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.