A prospective study of maternal 25-hydroxyvitamin D (25OHD) in the first trimester of pregnancy and second trimester heavy metal levels

Background: Vitamin D facilitates the absorption of calcium but may also increase absorption of other metals; the literature is conflicting. Objective: To examine whether 25OHD in the first trimester of pregnancy was associated with subsequent metals levels in the late second trimester of pregnancy. Methods: We used data from a sample of women in the LIFECODES pregnancy cohort (N = 381). 25-hydroxyvitamin D (25OHD) was measured with a chemiluminescence immunoassay in plasma samples drawn at 10 weeks of gestation. A panel of 17 metals and elements was measured in urine collected at 26 weeks of gestation. We used linear or logistic regression to estimate associations between 25OHD (dichotomous, linear, and in tertiles) and either urinary metal concentrations or the proportion of samples below the limit of detection, respectively. Multivariable models included urinary specific gravity, age, race/ethnicity, education, body mass index, insurance type, gestational age, and season. Results: After multivariable adjustment, low 25OHD was associated with a 47% increase in lead level, a 60% increase in tin level, and 1.58 times the odds of detectable tungsten. A 10 ng/ml increase in 25OHD was associated with a 12% decrease in tin and an 8% increase in molybdenum. While we had a small sample size, we found some evidence of effect modification by race. Women who reported their race as Black or were classified in the other race category, who also had low 25OHD, had 40% higher thallium than women with higher 25OHD and were more likely to have detectable beryllium and tungsten. These metals were not associated with low 25OHD in women who reported their race as White. Tin and lead were higher in women with low 25OHD in all race groups. Discussion: In total, further research is warranted to determine if vitamin D levels alter metal levels, and to elucidate the shape of the association for each metal across a range of corresponding 25OHD levels, and longitudinally, across pregnancy. This is especially true for pregnant people as exposure to metals during pregnancy has health consequences for the fetus.

Automated summary

The study found that low 25OHD in the first trimester of pregnancy was associated with increased lead and tin levels, as well as higher odds of detectable tungsten in the late second trimester. Women who reported their race as Black or other races had higher thallium levels and increased likelihood of detectable beryllium and tungsten with low 25OHD. However, there was no significant association between metal levels and low 25OHD in women who identified as White.