Vitamin D deficiency during pregnancy shown to impact the health of both mothers and babies in developing countries
September 14, 2018
Our next blog is by Dr Paige van der Pligt, Lecturer Nutrition and Dietetics and International Nutrition, Institute for Physical Activity and Nutrition, School of Exercise and Nutrition Sciences, Deakin University.
Last week was Women’s Health Week: 3-7 September 2018. To build on the momentum of this event, Dr van der Pligt has been invited to discuss her recent research publication entitled “Associations of Maternal Vitamin D Deficiency with Pregnancy and Neonatal Complications in Developing Countries: A Systematic Review”, which was published in Nutrients in May.
Pregnancy is a key life stage for any woman. The health of women during pregnancy impacts not only her pregnancy outcomes and birth experience, but it is critical for the health of her baby in both the immediate and the long term. During pregnancy it is essential that a woman attains adequate nutrition including vitamins and minerals to support her baby’s health, growth and development.
Vitamin D has come to receive much attention in Australia as currently one third of Australian adults over the age of 25 years are estimated to be vitamin D deficient. Globally, deficiency has been estimated to affect around one billion people. It is an essential vitamin for regulation of calcium absorption and promoting good bone health. In pregnancy, vitamin D plays a role in gene expression and if the mother is deficient, her baby will most likely be born deficient. Maternal vitamin D deficiency has been linked with a number of pregnancy complications as well poor growth, rickets in infancy and childhood obesity.
In Australia, women born in Asia and Africa or from culturally diverse backgrounds and those who are dark skinned are particularly ‘at risk’ for vitamin D deficiency. Throughout developing countries, however, the situation tends to be worse and in regions across Asia, the Middle East, Africa and Latin America, rates of vitamin D deficiency have been found to be substantially high. As sunlight is the best source of vitamin D, having dark skin pigmentation, wearing covered clothing for cultural or religious reasons or spending the majority of time indoors and away from sunlight (sunlight is the best provider of vitamin D) are well established risk factors for deficiency and are common practices among women in many developing regions. Many women across resource-poor countries may also be living in conditions whereby their micronutrient needs are not likely to be met due to chronically poor diets, or diets inadequate in oily fish and eggs (dietary sources of vitamin D).
Currently the World Health Organisation does not recommend routine testing or supplementation of vitamin D during pregnancy. This is due to there being a lack of good quality clinical trials providing a solid rationale for doing so. A critical first step in planning future pregnancy trials or public health strategies to target this issue is gaining an understanding of the evidence to date. To do this, we conducted a review of studies that assessed the impact of vitamin D deficiency during pregnancy in these high risk women, with complications and adverse health outcomes of the mother and the baby and the baby’s growth and development.
Thirteen studies from seven different countries across Asia, the Middle East and Africa were included in the review. Rates of maternal vitamin D deficiency ranged between 50 – 100% among different study populations, with the highest prevalence found in Chinese (100%), Turkish (96%), Iranian (89%) and Pakistani (89%) women. Despite mixed results, the majority of studies (ten out of the thirteen) found that maternal vitamin D deficiency was associated with at least one pregnancy complication for the mother and/ or baby. For the mother these included pre-eclampsia (high blood pressure in pregnancy), gestational diabetes (diabetes in pregnancy), emergency caesarean delivery and postpartum depression. For the baby, maternal vitamin D deficiency was associated with low birth weight and impaired growth (small for gestational age and stunting (reduced height for age)).
However, we found that the methods used to assess vitamin D varied widely across the studies included in our review, as did the stage and trimester of pregnancy during which vitamin D was measured and the criteria different countries use to define ‘deficiency’. This made comparison of the overall findings difficult. Therefore, unified approaches to assessing vitamin D, as well as culturally appropriate research methods are important considerations for tackling this issue in the future.
Pregnant women throughout the developing world represent a population group highly susceptible to vitamin D deficiency and associated health outcomes. Supporting the health of these women and women in Australia is so important. This work was a crucial first – step in understanding the research to date across regions where pregnancy support may be limited. I intend to focus my future work on assisting women during their pregnancies to attain optimal nutrition for their own health and the health of their baby. The issue of vitamin D deficiency in pregnancy is widespread, challenging and serious. But I’m optimistic that it is an issue that can be helped by conducting further research, understanding the differences in antenatal healthcare systems globally, considering cultural diversity, and with lots of hard work.
The citation for this publication is: Paige van der Pligt, Jane Willcox, Ewa A. Szymlek-Gay, Emily Murray, Anthony Worsley, Robin M. Daly. Associations of Maternal Vitamin D Deficiency with Pregnancy and Neonatal Complications in Developing Countries: A Systematic Review. Nutrients. 2018 10(5): 640. doi: 10.3390/nu10050640
To read the full manuscript click here.
Dr Paige van der Pligt, Lecturer Nutrition and Dietetics and International Nutrition,
Institute for Physical Activity and Nutrition, School of Exercise and Nutrition Sciences,
Deakin University.