This experiment was undertaken to investigate the effect of splenectomy on the hematology and maintenance of pregnant rats. Those animals that had shown regular 4 or 5 day estrous cycles for more than two cycles were used. The day after mating ws designated Day 0 of pregnancy. Spleen was removed from Day 0(early), 6(middle) and 13(late) of pregnant rat, respectively. Blood was collected on Day 1, 7, 14 and 21 of the pregnancy. 1. The total serum protein was increased significantly (P<0.05) to the progress of pregnancy in control rat. All rats that splenectomized groups were decreased significantly(P<0.05) at Day 21 of pregnancy than control rats. 2. Albumin was not significantly changed. 3. Globulin was decreased significantly(P<0.05) between contol and middle treatment at Day 7, 14 of pregnancy. 4. Glucose was increased for the due to the pregress of pregnancy. It was no significance differences among the each groups. 5. Rate of abortion was increased in groups of early and middle of splenectomy compared with control. 6. Period of pregnancy was delayed in middle and late splenectomized gruops companed with control. 7. Litter size was lowed significantly (P<0.05) in early and middle splenectomized groups compared with control.