Fluctuations of micronutrients during pregnancy in Lianyungang, Jiangsu, China: A prospective longitudinal cohort study

Pregnancy is accompanied by substantial physiological adaptations that may alter maternal micronutrient concentrations. A prospective longitudinal pregnancy-neonatal cohort of 51 healthy pregnant women was established at 6-8 weeks of gestation in Lianyungang, Jiangsu, China, confirmed by fetal heart and bud on B-ultrasound. Pregnancy complications, outcomes, and neonatal health at day 42 were confirmed. Forty-three women who completed all assessments and had uncomplicated pregnancies with favorable maternal and neonatal outcomes were included in the final analysis. Whole-blood trace elements and serum vitamins were quantified during the first trimester (12.3 ± 0.9 weeks), second trimester (25.6 ± 1.2 weeks), and third trimester (32.7 ± 2.3 weeks) using ICP-MS and UHPLC-MS/MS. The results showed that copper, calcium, and vitamin D peaked in the second trimester, whereas iron, zinc, magnesium, and lead reached their nadir in the second trimester. Meanwhile, manganese and vitamins E and K increased progressively throughout gestation. In contrast, several B vitamins showed an overall downward trend, while vitamin B12 remained relatively stable. These findings demonstrate clear trimester-specific changes in maternal micronutrient levels during healthy pregnancy. Given the relatively small sample size, these longitudinal data provide preliminary evidence to inform the establishment of region-specific and trimester-specific reference intervals and deficiency thresholds for micronutrients in healthy pregnant women.