Pregnancy is accompanied by hormonal changes. These relate mainly to progesterone and placenate growth factor. Hemodynamic changes are also observed. in a sickle cell pregnant woman, all these changes have a direct effect on hypoxia. This is responsible for the polymerization of HbS. The latter causes the sickling of sickle red blood cells. sickling of red blood cells is responsible for hemolysis and vasoocclusion, two major acute manifestations during pregnancy in a sickle cell patient.