Nonlinear Relationship Between Maternal and Cord Blood Vitamin B12 and Folate from a Chinese Population-Based Study

Purpose: There remains a data gap on vitamin B-12 and folate level in maternal and child populations. This study aimed to assess the status of vitamin B-12 and folate in maternal serum (MS) and umbilical cord serum (UCS).Materials and Methods: This was a planned secondary analysis of a case-control study. A total of 858 pregnant women during late pregnancy and their newborns in the hospitals of China were included. Maternal peripheral venous blood and neonatal umbilical cord blood were collected to determine serum vitamin B-12 and folate concentration. Relationship of vitamin B-12 or folate concentration between MS and UCS was assessed by a quantile regression model and the non-linear relationship between them was examined.Results: Nutritional status of serum folate was better than that of vitamin B-12. Prevalence of deficiency in MS vitamin B-12 and folate was 73.4% and 14.2%, respectively and these figures were about 17.8% and 0.1% in UCS. Both vitamin B-12 and folate levels in UCS were significantly higher than those in MS (vitamin B-12: 321.0 pg/mL vs 158.3 pg/mL, folate: 16.5 ng/mL vs 7.0 ng/mL, P <0.001). The median UCS-MS ratio of vitamin B-12 and folate was 2.0 (95% CI: 1.94-2.06) and 2.4 (95% CI: 2.30-2.53), respectively. The levels of folate and vitamin B-12 in UCS increased nonlinearly with their increase in MS which presented an inverted U-shaped curve.Conclusion: Deficiency in vitamin B-12 and folate in the women during late pregnancy in China is prevalent. Nutritional status of the two vitamins in umbilical cord serum is correlated nonlinearly with that in maternal serum. Folic acid supplementation may be accompanied with vitamin B-12 to improve status of vitamin B-12 and folate during pregnancy.