Measurement of serum vitamin B12-related metabolites in newborns: implications for new cutoff values to detect B12 deficiency

Abstract

Objective

Our aim was to determine the prevalence of maternal and neonatal vitamin B12 (vit-B12) and folate deficiencies, a new cutoff value of serum vit-B12 in newborns using vit-B12-related metabolites and also cutoff values of homocysteine (Hcy), propionyl (C3) carnitine, and methyl malonic acid (MMA) in newborns using a vit-B12 cutoff value of 200 pg/mL.

Methods

Healthy pregnant women (without iron deficiency) and 98 healthy, term, singleton babies were included. Blood samples were obtained from women 0–8 h before birth and from cord blood during birth for hemogram and to measure serum vit-B12, folate, and Hcy levels. Maternal and cord blood serum vit-B12 levels were classified as low < 200 pg/mL, marginal 200–300 pg/mL, and normal ≥ 300 pg/mL. Neonatal urine MMA levels were analyzed in mothers with a vit-B12 concentration < 300 pg/mL. C3 carnitine levels of newborns were acquired from extended newborn screening. Receiver operating characteristics curve (ROC) analysis was used for serum vit-B12, urine MMA, C3 carnitine, and Hcy.

Results

Of total, 98 pregnant women (28.6 ± 5.5-year-old) and 98 newborn were included. Vit-B12 level was lower than 300 pg/mL in 93% of the pregnant women and 61% of cord blood samples. Folate deficiency was not found in either group. There was statistically significant negative correlation between baby C3 carnitine, cord blood folate (r = −0.265, p = .008) and cord blood vit-B12 (r = −0.220, p = .029). In backward stepwise linear regression analysis, maternal vit-B12 level exerted the most marked effect on cord blood vit-B12 level (adjusted R² = 0.457). In ROC analysis, the Hcy cutoff value was 4.77 µmol/L (68.4% sensitivity, 58.3% specificity, p = .012) for the detection of vit-B12 deficiency.

Conclusion

Vit-B12 deficiency remains an important health issue for pregnant women and newborns. Our study revealed a cutoff value for Hcy for the detection of nutritional vit-B12 deficiency that could be used in practice for newborns.

Keywords:

• Folate
• homocysteine
• newborn
• urine methylmalonic acid
• vitamin B12 deficiency

Acknowledgments

The authors thank to Mr Jeremy Jones for editing and proofreading our manuscript and to the nurses, and all personnel working in the Department of Obstetrics and Gynecology of Istanbul Medical School for their assistance about collecting the data.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by Scientific Research Projects Coordination Unit of Istanbul University [Project no: 4107].