Serum Vitamin B₁₂ Levels During the First Trimester of Pregnancy Correlate with Newborn Screening Markers of Vitamin B₁₂ Deficiency

Introduction. Low maternal vitamin B₁₂ status is a risk factor for various adverse pregnancy outcomes. Although vitamin B₁₂ deficiency is not a primary target of newborn screening (NBS) programs, measurements of propionylcarnitine (C3) and its ratios with acetylcarnitine (C3/C2) and palmitoylcarnitine (C3/C16) may incidentally identify vitamin B₁₂-deficient newborns. The objective of this study was to measure vitamin B₁₂ levels in women during the first trimester of pregnancy, evaluate predictors of these concentrations, and study their relationship with newborn screening results. Design: Vitamin B₁₂ concentrations were evaluated in 204 women during the first trimester of pregnancy and possible confounding factors were analyzed. After giving birth, data of their newborns (189) were collected (sex, gestational age, birthweight) and the acylcarnitine profile obtained by tandem mass spectrometry during NBS was analyzed. To assess the effects of the variables on vitamin B₁₂ serum concentrations and newborn screening markers, stepwise multiple linear regression models were used. Results: The mean serum concentration of vitamin B₁₂ was 370.8 pmol/L (502.4 pg/mL) (SD 142.81). Vitamin B₁₂ concentrations were significantly lower in smokers (p = 0.027), and in women with low meat consumption (p = 0.040). There was a significant inverse correlation between mothers’ vitamin B₁₂ concentrations and their children’s C3 (r = - 0.24; p = 0.001), C3/C2 (r = - 0.23; p = 0.002) and C3/C16 levels (r = - 0.20; p = 0.006). Conclusions: Newborn screening markers (C3, C3/C2, and C3/C16) present an inverse correlation with maternal vitamin B₁₂ status in the first trimester of pregnancy. Regarding factors that may influence maternal serum vitamin B₁₂ levels during the first trimester, smoking seems to have a negative effect, and meat consumption a positive effect.