Abstract： Objective To investigate the etiology and clinical characteristics of pregnancy-emerged thrombocytopenia.Methods A retrospective analysis was conducted on clinical data of 159 pregnancies with thrombocytopenia,who were admitted to Peking University People's Hospital from January 2000 to January 2010.All the patients recruited in this study had no history of blood or immune system disease before pregnancy,and thrombocytopenia was the predominate clinical manifestation during pregnancy,with platelet counts less than 100 × 109/L at least twice during pregnancy.The thrombocytopenia should not be induced by drugs,viral infections,preeclampsia or hemolysis,elevated liver enzymes,and low platelets syndrome (HELLP).All cases were followed up.The general condition,the onset time of thrombocytopenia,platelet changes,accompany symptoms,maternal and perinatal outcomes as well as follow-up conditions were compared based on the etiology.Results ( 1 ) Etiology:among the 159 cases,101 (63.5％) were diagnosed gestational thrombocytopenia (GT) ;43 ( 27.0％ ) were idiopathic thrombocytopenic purpura(ITP) ;9 ( 5.7％ ) were blood system diseases,including 4 cases of megaloblastic anemia( MA ),2 cases of aplastic anaemia (AA),and 3 cases of myelodysplastic syndrome(MDS).Six cases (3.8％)were diagnosed immune system diseases,including 3 cases of systemic lupus erythematosus ( SLE),2 cases of antiphospholipid syndrome (APS),and 1 case of Evans syndrome.(2)Maternal and perinatal outcomes:pregnancy induced hypertension was diagnosed in 21 cases ( 13.2％ ),abnormal glucose metabolism in 13 cases ( 8.2％ ),anemia in 44 cases ( 27.7％ ) and preterm delivery in 18 cases ( 11.3％ ).Twenty-nine cases ( 18.2％ ) were treated with corticosteroids or gamma globulin during pregnancy.The average gestational week was 38 weeks.Fifty-five cases ( 34.6％ ) underwent vaginal delivery,104 cases ( 65.4％ ) received cesarean section.Postpartum hemorrhage was observed in 34 cases (21.4％),and puerperal infection happened in 2 eases ( 1.3％ ).No maternal death was found.In a total of 160 fetuses (including twins),there were 157 live births.Three cases of fetal death and 2 cases of early neonatal deaths were observed.Fetal growth restriction was observed in 4 cases,and neonatal thrombocytopenia was seen in 6 cases.No intracranial hemorrhage was detected.(3)The onset time of thrombocytopenia:among the 159 cases,29 cases ( 18.2％ ),67 cases (42.1％ ),63 cases (43.6％) of thrombocytopenia were detected in the first,second and third trimester,respectively.There was a significant difference of the onset time of thrombocytopenia between GT and ITP groups( P ＜ 0.05 ).Patients with GT tended to have a later onset of thrombocytopenia,which mainly happened in the second and third trimester,while patients with ITP tended to happen in the first and second trimester.(4)The degree of thrombocytopenia:the cases with the minimum platelets level of (51 - 100) × 109/L,(31 - 50) × 109/L,( 10 - 30) × 109/L,＜ 10 × 109/L during pregnancy were 75 (47.2％ ),39 (24.5％ ),31 ( 19.5％ ),14( 8.8％ ) respectively.There was a significant difference between GT and ITP groups in the lowest platelets level (P ＜ 0.01 ).(5)Thrombocytopenia accompany with anemia:among the 159 cases,there were 44 cases (27.7％ ) accompanied with anemia.The proportion was 9.9％ ( 10/101 ) in GT group,58.1％ (25/43) in ITP group,with significant difference(P ＜0.01 ).Anemia was also found in 5 cases in blood system disease group (5/9),and 1 case in immune system disease group (Evans syndrome,1/6).Pancytopenia was observed in 2 cases with ITP (4.7％,2/43 ) and 3 cases with blood system disease ( AA:1 cases,MA:2 cases,3/9).(6) The recovery of the platelets counts postpartum:the postpartum follow-up periods were 7 months to 10 years.Patients recovered within 1 week,6 weeks,6 months postpartum were 66 cases ( 41.5％ ),43 cases ( 27.0％ ),17 cases ( 10.7％ ) respectively.The platelets counts did not recover within 6 months postpartum in 33 cases(45.7％ ).Conclusions GT is the leading cause of pregnancy-emerged thrombocytopenia followed by ITP.There are significant differences between GT and ITP in the onset time of thrombocytopenia,the lowest platelets level,the proportion of anemia accompanied and the postpartum recovery.Other etiologies including immune and blood system diseases are rare.The relevant examinations should be taken for etiology and differential diagnosis.