Folic acid is often taken daily, by those who have hereditary spherocytosis, to prevent anemia through folate deficiency. A typical dosage is perhaps between 1mg and 5mg per day. Folic acid is also important during pregnancy, to prevent neural tube defects in the baby, so it’s recommended that every pregnant woman take a 400µg supplement every day. This should be in addition to any folic acid that you are taking for hereditary spherocytosis, although, if you are already taking 5mg per day, then this is probably acceptable. For more information on folic acid, see the article Treating spherocytosis with vitamins.
If you still have your spleen, then it is likely that you will become more anemic while pregnant, with a significant increase in the rate at which red blood cells are broken down (rate of hemolysis). In some cases, the anemia can become serious enough to require blood transfusion, both during pregnancy and for a few months after. After giving birth, the level of anemia slowly returns to its previous point. There is no increased risk of miscarriage associated with this additional anemia.
A woman with a mild form of hereditary spherocytosis might only be diagnosed with hereditary spherocytosis when she becomes pregnant, as a result of this additional anemia.
If you have had your spleen removed (splenectomy) then there is not normally an increase in anemia associated with pregnancy. However, there could be problems related to high levels of platelets. After splenectomy, platelet levels rise. These high platelet levels normally last just a few weeks, but can, occasionally, remain for years. High platelet levels can cause internal clotting and when this occurs in the placenta, it can cause miscarriage. If you have high platelet levels during pregnancy then you should consider taking aspirin to help prevent clots, especially if you have a history of miscarriage.
During pregnancy, it might be useful to prearrange for the child to be tested for hereditary spherocytosis once they are born. This can help diagnose any problems that can occur immediately after birth, such as jaundice.