Vitamin D insufficiency in early pregnancy highly prevalent in SG

A local study has raised concerns about a high rate of hypovitaminosis D in early pregnancy in Singapore.

In a cohort of pregnant women in their first trimester at the antenatal outpatient clinic of the KK Women’s and Children’s Hospital (KKH), only 2.2 percent had sufficient vitamin D levels (≥30 ng/ml). [PLoS One 2024;19:e0300063]

Almost half of the remaining participants (49.5 percent) fell into the insufficient vitamin D category, while 46.2 percent were in the moderately deficient and 2.2 percent were in the severely deficient categories.

“All women who were severely deficient were Chinese, [and] none of the Indians or Malays included in this study had sufficient vitamin D levels,” the investigators noted.

Additionally, vitamin D deficiency was negatively correlated with weight and positively correlated with age. However, in a multivariable analysis, only body mass index (BMI) remained significantly associated with vitamin D deficiency. Each 5-kg increase in weight was associated with 23-percent greater likelihood of being vitamin-D deficient (odds ratio [OR], 1.23, 95 percent CI, 1.01–1.50; p=0.043). This held true even when age was factored in (OR, 1.24, 95 percent CI, 1.01–1.53; p=0.042).

Meanwhile, participants with periconceptual multivitamin supplementation had 2.10-ng/mL higher vitamin D levels than those who did not take such supplements (p=0.047). Also, participants who got less than an hour of sun exposure daily were twice as likely to use vitamin D supplements compared with those who had more sun exposure.

The study population comprised 93 women (mean age 32.1 years, average gestational age 12.2 weeks), of which 87 percent were Chinese, 7 percent were Malay, 3 percent were Indian, and 3 percent of other races. Their mean weight was 58.1 kg, with an average BMI of 22.5 kg/m². The mean 25-OH vitamin D levels were 20.0 ng/ml.

Limited sun exposure

According to the investigators, there may be several reasons explaining the high prevalence of hypovitaminosis D in the first trimester in the local population.

First, a significant proportion of Singapore’s workforce, particularly those in professional, managerial, executive, and technical roles, have limited sunlight exposure due to the indoor nature of their jobs. Second, a multiethnic population, including Malays, typically wear clothing that covers most of the body for cultural reasons. Finally, among the Asian Chinese, lighter skin is often associated with beauty. [https://www.strategygroup.gov.sg/media-centre/population-white-paper-a-sustainable-population-for-a-dynamic-singapore/; BMC Public Health 2006;6:1-7]

Among Indians and Malays, on the other hand, increased skin pigmentation is a possible contributor to vitamin D deficiency, the investigators added. “With more melanin, it’s been shown to absorb more ultraviolet radiation causing less cutaneous production of vitamin D.”

KKH generally observes the guidelines set by the Royal College of Obstetrics and Gynaecology (RCOG) and the National Institute for Health and Care Excellence (NICE) from the UK. These guidelines recommend screening patients in high-risk groups including being darker-skinned, having limited exposure to sun, and having BMI ≥30 kg/m². [https://www.rcog.org.uk/media/lcfn54fw/healthy-eating-vitamin-supplements-pregnancy-large-print-patient-information.pdf; https://www.nice.org.uk/guidance/ph56]

“However, there is inapplicability of such guidelines to our local population who are predominantly Chinese with lighter skin. Locally, our Health Promotion Board advises 2.5 mcg of vitamin D in our diet, but screening of vitamin D deficiency has not been suggested in pregnant patients. The advice of 2.5 mcg supplement is also well below the suggestion of 10 mcg by RCOG and NICE,” the investigators pointed out. [https://www.healthhub.sg/live-healthy/recommended_dietary_allowances]

“Our study suggests that standard supplementation of vitamin D and screening of vitamin D levels for at-risk groups should be advised in our local context,” they added.