The dose of folic acid per day for treating megaloblastic anaemia in pregnancy
Folic acid deficiency in Pregnancy

In nonpregnant women, the folic acid requirement is 50 to 100 μg/day
During pregnancy, requirements are increased and 400 μg/day is recommended 

The earliest biochemical evidence is low plasma folic acid concentrations 
Normal serum folate levels

Non Pregnant women: 5.4-18ng/ml
1st trimester: 2.6-15ng/ml
2nd trimester: 0.8-24ng/ml
3rd trimester: 1.4-20.7ng/ml


Early morphological changes usually include neutrophils that are hypersegmented and newly formed erythrocytes that are macrocytic
 As the anaemia becomes more intense, peripheral nucleated erythrocytes appear, and bone marrow examination discloses megaloblastic erythropoiesis
The fetus and placenta extract folate from maternal circulation so effectively that the fetus is not anaemic despite severe maternal anaemia

Treatment

 As little as 1mg of folic acid administered orally once daily produces a striking haematological response
By 4 to 7 days after beginning folic acid treatment, the reticulocyte count is increased, and leukopenia and thrombocytopenia are corrected
American College of Obstetricians and Gynecologists (2013c) have recommended that all women of childbearing age consume at least 400 μg of folic acid daily

Increased need of Folic acid

Multifetal pregnancy
Hemolytic anaemia
Crohn disease
Alcoholism
Inflammatory skin disorders
400 μg
1 mg
5mg
2 mg