Preconception folic acid advice

What it is

To prevent neural tube defects in newborns, the U.S. Preventive Services Task Force recommends folic acid, 0.4-0.8 mg daily, for all women who are planning on or are capable of becoming pregnant. It is an A recommendation, so the advice goes to every woman who could become pregnant and not only to those with a known risk. The daily folate requirement in pregnancy is put at 800 mcg/day.

Causes and risk

Folate deficiency arises by four routes, and a woman on any of them needs the advice repeated and her intake checked:

• Greater demand: hemolytic anemia and multiple pregnancies.
• Lower intake or malnutrition, including alcohol.
• Lower absorption: malabsorption such as celiac disease, gastric bypass surgery, and drugs including phenytoin, methotrexate, sulfasalazine and trimethoprim.
• Greater loss: hyperemesis gravidarum and dialysis.

How it is diagnosed

Folate deficiency anemia shows a fall in Hb, Retic, WBC and Plt with a raised MCV. The blood film is that of a megaloblastic anemia: macrocytosis with hyper segmented neutrophils. The biochemical profile shows a low serum folic acid with a raised LDH and a normal B12, while homocysteine is raised and methylmalonic acid stays normal.