Effect of sun exposure and 25-hydroxyvitamin D status among pregnant women in Antwerp, Belgium

Abstract

Vitamin D is a fat-soluble vitamin obtained by the human body in two ways: dietary intake from mainly fatty fish, eggs, and fortified food; and endogenous production in the skin after UVB exposure. In pregnancy, vitamin D concentration is 2-fold higher owing to the activity of placental 1-α-hydroxylase [1]. There is increasing evidence that vitamin D affects maternal and fetal well-being, and a deficiency is associated with a higher risk of developing pre-eclampsia, growth restriction, multiple sclerosis, schizophrenia, diabetes, and asthma [2]. Immigrants in northern countries, especially those who are dark skinned and/or covered by traditional clothing, are more prone to vitamin D deficiency in pregnancy [3,4]. The aim of the present study was to investigate the prevalence of vitamin D deficiency in a sample of the pregnant population in Antwerp and the effect of coverage by traditional clothing. The study was approved by the institutional Ethics Committee and patients provided written informed consent prior to enrolment. From August 1, 2009, until June 30, 2010, women were recruited at the prenatal clinic of Antwerp University Hospital. 25hydroxyvitamin D level was determined in 369 consecutive women and each patient was categorized according to their exposure to the sun. The mean age of the women was 29.3±4.6 years. The median gestational age was 24 weeks (range, 4–37 weeks), and the majority (46.6%) were primiparous (n=172). A total of 90 (24.4%) women were taking multivitamin preparations containing 10 μg of vitamin D (400 IU). The mean vitamin D level among all patients was 21.8± 11.7 ng/mL. There was no effect of age, parity, supplement intake, or gestational age on vitamin D level. There was a statistically significant influence of month of blood sampling (Fig. 1) and sun exposure (Pb0.001). The women were divided into 3 categories of sun exposure: 311 (84.3%) uncovered women had a mean vitamin D level of 23.6± 11.2 ng/mL; 37 (10.0%) women who wore head covers only had a mean level of 13.2±8.0 ng/mL; and 21 (5.7%) women who were completely covered except for their face had a mean level of 11.2± 11.8 ng/mL. There was a significant difference between the 3 groups (ANOVA, Pb0.001). The mean value of our population (21.8±11.7 ng/mL) was below the reference range of 30 ng/mL. Those found to be deficient were offered an extra dose of 20 μg of vitamin D (Steovit D3; Nycomed, Brussels, Belgium). The women who were covered were mostly immigrants who may have lived in poorer social circumstances; therefore, their deficiency may also have been attributable to poor dietary intake. Dietary intake of vitamin D should be investigated in further studies, as well as darkness of skin and ethnicity. Despite the small sample size and local recruitment, these data demonstrate that fully covered pregnant women in Antwerp suffer alarmingly low levels of vitamin D. International Journal of Gynecology and Obstetrics 116 (2012) 76–86BRIEF COMMUNICATIONS