The risk of vitamin D deficiency is the world's highest in developing countries in Asia, the Middle East, Africa and Latin America. This has led to a heightened risk of adverse maternal and neonatal health outcomes, which is compounded by limited research in these countries.
A plethora of problems
Researchers at Deakin University and La Trobe University in Australia conducted a review to assess the link between maternal vitamin D deficiency and adverse health outcomes.
They reviewed English-language literature from 13 observational studies conducted between 2000 and 2017 in developing countries: six of the studies assessed both maternal and neonatal outcomes, four assessed only maternal outcomes, and three assessed only neonatal outcomes.
The researchers reported that the prevalence of vitamin D deficiency ranged from 51.3% to an alarming 100%. In addition, there was at least one significant association between vitamin D deficiency and adverse maternal and / or neonatal health outcomes in 10 of the studies.
These included pre-eclampsia in three studies, gestational diabetes in one study, postpartum depression in one study, emergency C-section delivery in one study, low birth weight in four studies, babies who were small for their gestational age in two studies, and stunting in one study.
The researchers added, however, that there was no relationship among multiple health outcomes, and that the vitamin D assessment methods used, criteria for defining vitamin D deficiency, and the season and trimester during which the studies were conducted, differed considerably across the board.
Developing nations lacking D
Vitamin D deficiency, especially among mothers (expectant and otherwise) and children, has long been a prevalent problem in developing countries.
In Palestine, vitamin D deficiency — among other micronutrient deficiencies — has been linked to autism in children.
In China, concerns over possible cognitive and physical development issues stemming from vitamin D deficiency have been raised.
The problem is particularly severe in South Asia, where school-going children in India are often vitamin D-deficient. In Pakistan, authorities have pushed for food fortification programmes targeting women and children who are often deficient in a variety of micronutrients, including vitamin D.
But while such programmes have been rolled out in countries like Pakistan, India and Bangladesh, progress has been slow, due in part to a lack of research and available information.
A dire need
For the current review, the researchers concluded: "This review showed that vitamin D deficiency during pregnancy is a widespread issue that can adversely affect the health of both women and children in developing countries.
"This study highlights the need to improve maternal vitamin D status in developing countries, in an effort to support best maternal and child health outcomes across these regions. However, current methods to assess VDD differ widely and a more unified approach would assist informing the development of suitable approaches to tackling this issue.
"Addressing the impact of maternal and neonatal VDD through high-quality, rigorous and culturally suitable research is key to informing well-designed RCTs targeting this issue. Future research should focus on strategies which include biological and lifestyle factors and preventative approaches that may be embedded into already existing antenatal care settings."
"Associations of Maternal Vitamin D Deficiency with Pregnancy and Neonatal Complications in Developing Countries: A Systematic Review"
Authors: Paige van der Pligt, et al.