Most Pregnant Women in Mediterranean Are Vitamin D Deficient

Becky McCall

May 21, 2015

DUBLIN — Low vitamin D during pregnancy is prevalent in the Mediterranean region, despite high levels of sunshine, prompting a call for greater awareness and action from public-health authorities there on this issue, say researchers.

"Sartorial, social, and cultural habits as well as the absence of preventive strategies seem to negate the benefits of sun exposure," stressed Dr Spiros Karras (Aristotle University of Thessaloniki, Greece), who presented the findings in a poster at the European Congress of Endocrinology (ECE) 2015.

Dr Karras said he would like to encourage pregnant women to raise the issue with their physicians and have the opportunity to be screened and tested for vitamin-D deficiency, if appropriate. Low vitamin D during pregnancy has been associated with preeclampsia, gestational diabetes, disorders in bone formation, higher risk of emergency cesarean delivery, and premature birth.

"We need to inform public-health opinion of the benefits of vitamin-D supplementation during pregnancy, as well as increase awareness among physicians who are totally hostile to vitamin-D supplementation," which is the situation in Greece, he added.

Asked to comment on Dr Karras's work, Dr Nick Harvey (MRC Lifecourse Epidemiology Unit, University of Southampton, United Kingdom) said, "Using these findings in clinical practice needs more investigation."

The cost of testing for vitamin D needs to be taken into consideration when deciding whether widespread supplementation or targeted case finding is most appropriate, he added.

Some countries — for example, the United Kingdom and Canada — simply recommend vitamin-D supplementation for all pregnant women.

But in the United States, the American College of Obstetrics and Gynecology (ACOG) says vitamin D shouldn't be given routinely in pregnancy, other than in the form of a prenatal vitamin, until the results of ongoing randomized trials report.

And there is currently insufficient evidence to support a recommendation for screening all pregnant women for vitamin-D deficiency, although testing can be considered for pregnant women thought to be at increased risk, ACOG notes.

80% to 90% of Pregnant Women in Mediterranean Are Vitamin D Deficient

The aim of the study by Dr Karras and colleagues was to systematically review trials that investigated vitamin-D concentrations during pregnancy in the Mediterranean region (Spain, Italy, Greece, and Turkey) in order to determine predictors of hypovitaminosis D.

In doing so, the researchers aimed to explain the paradox that despite high levels of sunshine, low levels of vitamin D during pregnancy are common in Mediterranean women.

A total of 2649 pregnant women and 1820 neonates from 15 trials were included.

The primary outcome was a measure of maternal vitamin-D levels, although there was heterogeneity across the studies in terms of vitamin-D–deficiency criteria and methods of measurement, for example, which is a limitation, Dr Karras noted.

The researchers found that up to 90% of both mothers and neonates were deficient according to the less conservative criteria for vitamin-D deficiency of the US Institute of Medicine (IOM), which defines it as below 20 ng/L.

In Spain, Italy, and Greece, 70% to 80% of pregnant women had hypovitaminosis D, while in Turkey the rate was higher, at 90%.

The researchers also found that vitamin-D supplementation was not common practice, although Turkey is due to start a wide-scale program soon, Dr Karras noted.

"Specific factors were found to be highly prevalent in some countries and could predict vitamin-D deficiency — for example, whether women actually spend time in the sun," Dr Karras told Medscape Medical News.

"In Greece, physicians advise pregnant women to stay out of the sun for fear of skin cancer; they also use sunscreen, which blocks UVB, the primary source of vitamin-D production."

Other prognostic factors associated with low vitamin-D levels were dark skin, race, and dress habits. In Turkey, for example, women are often required to be covered, preventing sunlight from reaching the skin.

And "in Spain and Italy, there are many immigrant mothers with dark skin, who have particularly low vitamin D due to the nature of their skin," Dr Karras pointed out.

Target Screening to Women at Risk for Vitamin-D Deficiency

Dr Karras said he is not suggesting all Mediterranean women should be screened for low vitamin-D levels, "because it is not cost-effective, but certain women who are at higher risk, for example, women with dark skin."

Dr Kevin Cashman (School of Food & Nutritional Sciences, University College Cork, Ireland) agrees that the prevalence of low vitamin-D status is consistently higher in subsets of European populations with darker skin/ethnicity compared with white individuals.

Dr Cashman runs ODIN — a 4-year collaborative project aimed at preventing vitamin-D deficiency in European citizens.

However, he pointed out that the impact of vitamin D <50 nmol/L "for maternal health and that of the infant is not entirely clear as yet. The data are mixed — with evidence in support [of the effect of deficiency] but also suggestive of lack of effect with the various health outcomes mentioned."

And "other reviews [from the IOM in 2011 and the Endocrine Society in 2011] both suggested that while the association between vitamin D and nonskeletal health effects were interesting, more evidence was needed to confirm these, including infant health outcomes," he added.

Finally, adding his thoughts to the discussion, the outgoing president of the European Society of Endocrinology, Dr Philippe Bouchard (Pierre et Marie Curie University, Paris, France), said: "I think it's an important study, and such work should be encouraged. I think we need more study on the consequences of vitamin-D deficiency [in pregnancy]."

Drs Karras, Dr Harvey, Dr Cashman and Dr Bouchard have no relevant financial relationships.

European Congress of Endocrinology 2015. May 16-20, 2015; Dublin, Ireland. Abstract EP241

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