What causes low hemoglobin in pregnant women?

Pregnant women with low hemoglobin may be folic acid, vitamin b12, iron intake caused by anemia, may also be pre-pregnancy menstrual volume is relatively large, a variety of microelements and vitamin loss too much, did not get timely supplementation. Pregnant women anemia should strengthen nutrition, if necessary, can supplement iron, folic acid tablets and multivitamins.