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

There remains a data gap on vitamin B₁₂ and folate level in maternal and child populations. This study aimed to assess the status of vitamin B₁₂ and folate in maternal serum (MS) and umbilical cord serum (UCS).

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 B₁₂ and folate concentration. Relationship of vitamin B₁₂ or folate concentration between MS and UCS was assessed by a quantile regression model and the non-linear relationship between them was examined.

Nutritional status of serum folate was better than that of vitamin B₁₂. Prevalence of deficiency in MS vitamin B₁₂ and folate was 73.4% and 14.2%, respectively and these figures were about 17.8% and 0.1% in UCS. Both vitamin B₁₂ and folate levels in UCS were significantly higher than those in MS (vitamin B₁₂: 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 B₁₂ 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 B₁₂ in UCS increased nonlinearly with their increase in MS which presented an inverted U-shaped curve.

Deficiency in vitamin B₁₂ 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 B₁₂ to improve status of vitamin B₁₂ and folate during pregnancy.