You can drink iron tonic with the following:
I gallon of organic grape juice and add
1 cup raisin
1 cup apricot
1 cup figs
1/2 cup blackstrap molasses
5 tbsp blackberry concentrate
Let it sit on the counter overnight then put in the refrigerator.

Drink 4 ounces 3-4 times daily for a month or two

You cannot rush bone marrow. Best to tank up on iron, folic acid, B12 and vitamin C throughout you pregnancy. It helps to take this in addition to your prenatal vitamin well into your post partum time. All of your red blood cells are replaced in 120 days when the environment is optimized.

Increase iron rich foods like spinach, beets and meat with Vitamin C for better absorption