Serum Vitamin B12 Level: Physiological Effects in Pregnancy

Abstract

Vitamin B12 (Cyanocobalamin), a water-soluble vitamin is an essential nutrient required for maintenance of normal erythropoiesis, nucleoprotein and myelin synthesis, cell reproduction and normal growth. Vitamin B12 is a necessary cofactor in the methionine synthase reaction, which converts homocysteine into methionine. During pregnancy, Vitamin B12 is concentrated in the fetus mostly in the liver. Vitamin B12 deficiency is rare in the infant up to 4 months if mothers receive adequate Vitamin B12. Vitamin B12 deficiency (serum or plasma B12 <150 pmol/L or 304 pg/mL) is common in women of reproductive age, but geographic, socio-economic and cultural properties including nutritional habit may influence the prevalence of Vitamin B12 deficiency. It may reach up to 74% in rural Nepal pregnant women that affect in quality of their milk lead to adverse effects on growth and developmental of their infants. In clinic 18% to 20% of clinical macrocytosis (defined as an MCV > 100) is related to B12 deficiency. Vitamin B12 deficiency play role in myelin damage, accounting for the neurologic deficits, such as neuropathy and ataxia, loss of proprioception, ataxia, the development of peripheral neuropathy, and dementia. Physical examination of affected case show fatigue and pallor, jaundice, glossitis, diarrhoea, headaches, and neuropsychiatric disturbances. Vitamin B12 deficiency in mild or subclinical can be associated with cognition disorder especially in elderly and children while complications in pregnancy include abortion, preterm labour, secondary low birth weight, anencephaly, neural tube defects, deficiency of Vitamin B12 has been linked to a variety of abnormal neurological symptoms such as hypotonic muscles, failure to thrive, cerebral atrophy and developmental regression. Maternal plasma B12 in pregnancy is predictive of offspring cognitive performance at 9th year of age, Vitamin B12 deficiency in pregnancy is reason for infertility, IUGR, preeclampsia and early pregnancy loss, preconception level lower than 258 pmol/L (349pg/mL) may increase the chance of preterm delivery. A serum Vitamin B12 above 300 pg/mL is interpreted as normal, levels between 200 and 300 pg/mL are considered borderline, and below 200 pg/mL are considered deficient. Vitamin B12 insufficiency increases Risk of developing an autoimmune disorder. daily maternal Vitamin B12 supplementation (50 μg/day) during pregnancy through 6 weeks postpartum substantially improved maternal Vitamin B12 status, in spite of Vitamin B12 importance ‘WHO recommends just iron and folic acid to pregnant women. GUSTO study showed 48% of the women had Vitamin B12 insufficiency, and those with lower Vitamin B12 and high folate levels are prone to develop gestational diabetes. Early pregnancy B12 values are predictive of high fasting blood sugar in late gestation. Low B12 levels may be an independent risk factor for Gestational Diabetes Mellitus (GDM), particularly in obese women. Such mothers are older, more obese with lower mean B12 values than controls (184 vs 225 pmol/L) (249 vs 304 pg/mL). There is an association with high folate(12.2 ng/mL or more) to serum Vitamin B12 (306 pg/mL or more) and high plasma glucose. Key points There is a long time that researchers found the importance of Vitamin B12 importance in a healthy pregnancy process while WHO has not any guidelines about how to supply such vitamin to risky and non-risky pregnancy. Attention to nutrition (containing Vitamin B12) and supply of adequate Vitamin B12 is essential in pregnancy. The best time for supplying is before conception and best level of serum B12 is more than 306 pg/mL. In low serum Vitamin B12, all pregnancies should be considered high risk for preterm, GDM, and fetal anomalies. Giving high folate dose to Vitamin B12 deficient mothers can be hazardous. A successful nursing with breast milk feeding and having healthy smart infant depends on attention to serum Vitamin B12 level of mothers during nursing.