Idiopathic thrombocytopenic purpura (ITP) is an autoimmune disorder characterized by a low platelet count and mucocutaneous bleeding. The estimated incidence is 100 cases per 1 million persons per year1). ITP in adults is generally chronic, the onset is often insidious, and approximately twice as many women as men are affected. It is estimated that ITP occurs in 1 or 2 cases out of every 1,000 pregnancies, accounting for approximately 3 percent of women who have thrombocytopenia at the time of delivery2). Although pregnancy is not discouraged in women with preexisting ITP, maternal and fetal complications can occur, and additional monitoring and therapy may be needed3).

In the past decade, our understanding of ITP in pregnancy has improved. However, most of the previous studies have focused on the outcomes of the infants. There has been limited information regarding ITP outcomes in obstetric patients, including hemostatic risk in delivery and the likely necessity of treatment during pregnancy. For this reason, we reviewed the outcomes and clinical aspects of pregnant patients with ITP.

In this study, about half of the pregnancies in ITP patients were diagnosed during pregnancy. Patients occasionally present for the first time with severe thrombocytopenia during pregnancy. When pregnant women present with thrombocytopenia, it is often impossible to distinguish underlying ITP from incidental thrombocytopenia of pregnancy. Often, one must wait until the postpartum interval to determine whether the patient had true ITP or incidental thrombocytopenia of pregnancy. Incidental thrombocytopenia of pregnancy resolves itself following delivery, whereas ITP typically does not.

We observed that the mean platelet counts before pregnancy, during pregnancy, and at delivery were similar. However, the platelet counts tended to fall at the third trimester. This finding was consistent with previous studies reporting that women with previously diagnosed ITP may experience an exacerbation in pregnancy4), with the nadir platelet count usually occurring in the third trimester2). Regardless of platelet counts, most of the pregnancies did not show hemostatic impairment during pregnancy or at delivery.

During pregnancy, most of the patients received therapy to raise platelet counts. The decision to treat a woman for thrombocytopenia was made by the attending physician and was based on several factors including platelet counts, signs and symptoms of bleeding, and need for invasive intervention. The therapeutic strategies in this study seem to involve overtreatment because platelet transfusion was performed even in patients with appropriate platelet counts. In the past decade, it was commonly assumed that many pregnant women with ITP would experience complications and would sometimes suffer from fatal thrombocytopenic disorders during pregnancy7,8). These conclusions led to aggressive interventions that ranged from the administration of multiple medications to the pregnant mother with ITP or the performance of splenectomy during pregnancy, and often included delivery of the infant by cesarean section. Although the understanding of thrombocytopenia in pregnancy has evolved considerably over the last decade, the optimal diagnostic and treatment strategies for ITP in pregnancy remain controversial. The lack of prospective trials investigating ITP in pregnancy has meant that physicians frequently rely on personal experience and anecdotal evidence to manage these patients. However, recent studies have clarified several important aspects of ITP in pregnancy. Although the platelet count often drops in pregnant ITP patients, serious morbidity and mortality are distinctly uncommon for the mothers9,10). We also noted that most of the pregnancies did not show hemostatic impairment during pregnancy. However, in this study, the incidence of severe thrombocytopenia (below 20,000/mm³) at delivery was 6.5% (2 patients). One of two patients experienced complications with major bleeding, which suggests that hemorrhagic complications do occasionally occur which require careful monitoring and management.

It has been reported that, ideally, maternal platelet counts should be maintained above 30,000/mm³ throughout pregnancy and above 50,000/mm³ near full-term to minimize the need for platelet transfusions11). Asymptomatic patients with platelet counts above 20,000/mm³ do not require treatment until delivery is imminent, but should be carefully monitored, both clinically and hematologically. It is also known that platelet counts of above 50,000/mm³ are regarded as safe for normal vaginal delivery. A platelet count of above 50,000/mm³ is also safe for cesarean section, but would preclude the use of epidural anesthesia, for which the platelet count should be above 80,000/mm³ 11). In this study, the most commonly used therapy at delivery consisted of platelet transfusion. Because of rapid correction of platelet counts after platelet transfusion and lack of time from recognition of thrombocytopenia to delivery, the attending physician tended to overuse platelet transfusion. There was no significant difference in hemorrhagic complications between the platelet transfusion group and non-transfusion group.

Generally, cesarean section was preferred against among the general population in pregnancies with ITP. The strategy behind delivery by C-section was the theoretical reduction in the risk of intracranial hemorrhage in infants born to mothers with ITP. However, Cook and colleagues reviewed literature that included 474 pregnant women with ITP and reported that the incidence of intracranial hemorrhage among neonates with severe thrombocytopenia (below 50,000/mm³) was 4% after cesarean section and 5% after vaginal delivery12). The occurrence of postpartum anemia requiring transfusion was higher among those undergoing cesarean section13). Therefore, the mode of delivery should be determined by obstetric indication only. The use of delivery method was similar for that of both cesarean section and vaginal delivery in our study and there were no differences in hemostatic complications between the two groups.

Because this study was retrospectively analyzed, the incidence and severity of thrombocytopenia in neonates could not be evaluated. However, none of the full-term newborns showed any hemorrhagic complications or needed any treatment to raise their platelet counts. It has been reported that the overall frequency of thrombocytopenia in infants is quite low, and about 4% of infants will have a birth platelet count of less than 20,000/mm³, while approximately 1% will have significant bleeding complications. Other studies reported that 9% of infants born to women with ITP are born with platelet counts below 50,000/mm³, and counts often decrease during the first few days of life2,14). Numerous studies over the past two decades have documented that neonatal thrombocytopenia is both uncommon and unpredictable. Data from both prospective studies and retrospective studies give relatively consistent results15-20). Consequently, the risk of intracranial hemorrhage or other major bleeding complications is also uncommon.

In conclusion, our current results regarding ITP in pregnancy confirm the low hemorrhagic risk in infants and mothers. Most mothers with ITP can proceed with their pregnancies and deliver infants without complications. Since fetal risks from severe thrombocytopenia are rare, the delivery mode should be determined strictly by obstetric indications. ITP in pregnancy necessitates the management of two patients, the mother and her baby. Hence, the close collaboration of a multidisciplinary group composed of a hematologist, obstetrician, and pediatrician is essential.