I have sickle cell disease. If I contract fifth disease can there be complications?

Yes. Aplastic crisis, profound dropping of hemoglobin (so called iron count) due to suppressed red cell production from bone marrow is a well known complication.
Yes. Parvovirus is the virus that causes 5th disease. It can cause a decrease in red blood cell production. Persons with blood conditions like sickle cell disease that cause shortened survival of red cells can become very anemic very quickly if their red cell production slows down. They may need blood transfusions to keep their blood count at a safe level.