Prevalence of vitamin D deficiency in pregnant women and their babies in Bhaktapur, Nepal

Vitamin D deficiency is observed worldwide in pregnant women and their neonates [1–5]. Maternal vitamin D deficiency is associated with various problems in their babies such as preterm delivery, low birth weight, neonatal hypocalcemia etc. that can be associated with neonatal deaths [6].

Vitamin D deficiency can be present in people who have a vegetarian diet, who are not adequately exposed to sunlight, or consume a low amount of dairy products. Vitamin D is transferred to the fetus from mother. Vitamin D deficiency in mother can lead to deficiency in the newborn baby. Vitamin D and calcium requirements during pregnancy are higher than the normal recommended dose. But the exact dose of calcium and vitamin D supplementation is still debatable [7]. Human milk contains 15–50 IU/L of vitamin D which is inadequate to fulfill the daily requirement of the growing baby [8]. Hence exclusively breastfed babies might be at risk of vitamin D deficiency. The American Academy of Pediatrics (AAP) has recommended to supplement all exclusively breast fed neonates with 200 IU/day of vitamin D3 to prevent adverse events due to vitamin D deficiency [9].

Studies conducted in south-east Asian region have shown people living in this area are prone to vitamin D deficiency [10, 11], and its prevalence in some areas is more than 80% [12–14]. To our knowledge, vitamin D status in pregnant women and their newborn babies in Nepal has not been studied and the country is in high prone area. In this study we examine the prevalence of vitamin D and calcium deficiency among pregnant women and their babies in Bhaktapur, Nepal.

This study showed a high prevalence of vitamin D deficiency and a high prevalence of lower than desired level of calcium among pregnant women and their newborn babies in Bhaktapur, Nepal. The levels of the micronutrients in mothers had a linear relationship with those of newborn babies. To our knowledge, this is the first study specifically looking into the relationship of vitamin D level in pregnant women and their newborn babies in Nepal. Few studies showed high a prevalence of vitamin D deficiency in general population [15, 16]. In a study conducted in Nepal vitamin D deficiency (< 20 ng/ml) was observed in 81% of the pregnant women and serum calcium level was less than the desired value in 67% of the mothers [17].

Vitamin D deficiency is observed worldwide in all age groups [13–18]. Deficiency during pregnancy and childbirth poses more threat to health than in other periods of life [4–6, 19, 20]. This can be prevented by nutrient supplementation. South Asia is considered to be high-risk area for vitamin D deficiency because of its geographical location and dark skin color of the people [10, 13]. A study done in a rural part of North India showed vitamin D deficiency (< 20 ng/ml) in 88.6% of adolescent girls and 74% of pregnant women [21]; similarly another study in the same region found 85% of pregnant women and 95% of their newborn babies had vitamin D deficiency with a positive correlation between maternal and cord blood vitamin D level [12]. Many studies have shown a positive correlation between maternal and babies’ vitamin D levels as vitamin D is transferred from mother to fetus via placenta [20, 22–24].

Pregnant women in Nepal are regularly supplemented with calcium and vitamin D3 tablets containing 500 mg of elemental calcium and 250 IU of vitamin D3 (cholecalciferol) after first trimester of pregnancy. The WHO has recommended 1 to 2 g of elemental calcium during pregnancy and child birth, but not a regular vitamin D supplementation during normal pregnancy [24–27]. However, the Royal College of Obstetricians and Gynecologists (RCOG) of the United Kingdom and the American College of Obstetricians and Gynecologists (ACOG) has recommended at least 400 IU of vitamin D3 supplementation during pregnancy [2, 28]. As the region is prone to vitamin D deficiency and studies have shown high prevalence of deficiency in the region, it should be considered to follow the recommendation of these Royal Colleges to provide at least 400 IU of vitamin D3 as a regular supplementation to Nepalese pregnant women.

Serum calcium is an important marker of vitamin D activity. An adequate amount of vitamin D is required for maintenance of calcium homeostasis [8, 28]. There is a risk of calcium deficiency when there is vitamin D deficiency. Positive correlation between maternal serum vitamin D and calcium with that of cord blood vitamin D and calcium level has been documented [1, 4, 12]. Determining vitamin D and calcium level in pregnant mothers can help us to predict their levels in newborns. In our study, the linear relationship is stronger for the vitamin D levels as compared to the calcium levels (adjusted coefficient of linear regression was 1.04 versus 0.53).

The study has some limitations. The study site was a non-governmental hospital; the services were not free of cost as that of governmental hospital, so the study population tended to be pregnant women of middle or higher socio-economic status. Due to this, the prevalence of vitamin D deficiency could have been underestimated. As the study was carried over only for 6 months the effects of seasonal variations could not be studied.

We have found a high prevalence of vitamin D deficiency among the pregnant women and their newborn babies in Nepal. Further large studies are needed to explore the possible causes of vitamin D deficiency. Regular adequate supplementation of vitamin D and calcium are needed during pregnancy.