The study conducted in government health clinics located at the Malaysian states of Selangor and Kuala Lumpur took place between November 2016 and January 2018, and involved 535 pregnant women who were in their third trimester.
The respondents’ vitamin D status were determined based on serum 25(OH)D analysis. They were required to fill in a vitamin D food frequency questionnaire and a sun exposure survey as well.
Results revealed that 42.6% of the respondents were vitamin D deficient (< 30 nmol/L) and 49.3% were vitamin D insufficient (30–50 nmol/L). Only 8% of the respondents had normal amounts of vitamin D (≥ 50 nmol/L).
Low dietary intake of vitamin D was found to be a major cause. Three in four of the respondents did not hit the recommended daily intake of 15μg of vitamin D.
On average, their vitamin D intake was between 6.7μg and 8.7μg/day, which was less than half or about half of the recommended intake.
Notably, a strong link was found between ethnicity and dietary vitamin D intake, with ‘the odds of having vitamin D deficiency reduced by 87% in non-Malays’, the researchers said.
They added that this finding was in line with previous studies, with religious and cultural practices highlighted as some of the possible factors.
“Muslim women are compulsory [sic] to cover their entire body parts and this reduces the probability of the Malay pregnant women in getting sufficient sunlight, which will then lower the vitamin D production in their bodies,” the researchers said.
The findings coincided with previous studies conducted in the same regions, including one from a tertiary hospital which found that 71.7% of the third trimester pregnant women had vitamin D deficiency and 21% had vitamin D insufficiency.
Low levels of vitamin D during pregnancy is a concern as this is linked with adverse obstetric outcomes, such as gestational diabetes and pre-eclampsia.
It is also associated with fetal intrauterine growth restriction and adverse outcomes, such as higher risk of premature birth, abortion, and childhood obesity.
The study showed that about 80.4% of the respondents’ vitamin D intake came from food sources.
Most of their vitamin D intake came from the consumption of fish and fish products (35.8%), followed by milk and milk products (28.2%), eggs (9.1%), and meat and meat products (3.9%).
On the other hand, one in three of the respondents said they took vitamin D supplements.
Vitamin D deficiency amongst pregnant women is also prevalent in Western countries and other parts of Asia.
For instance, the rate of prevalence ranged from 27% to 91% in the US, 39% to 65% in Canada, 45.0% to 100.0% in Asia, 19.0% to 96.0% in Europe, and 25.0% to 87.0% in Australia and New Zealand.
Researchers said that this study suffered from a number of limitations, including the inability to determine a causal effect relationship, since this was a cross-sectional study.
Also, out of the 3,982 pregnant women invited to participate in the study, only 535 consented and completed the study. As such, the study had a low response rate of 13.4%.
Researchers said this might lead to selection bias which could affect the external validity of the study.
In addition, vitamin D status was assessed only during the third trimester of pregnancy and the changes of vitamin D status during early pregnancy were unknown. This might affect the extent to which the research findings can be applied to other settings.
Other potential factors which may contribute to vitamin D levels, such as skin type, physical activity, season, or genetic background, were also not examined, hence further studies are recommended.
Source: PLOS Journal
Vitamin D deficiency during pregnancy and its associated factors among third trimester Malaysian pregnant women
Authors: Fui Chee Woon, et al