Unexplained periparturient thrombocytopenia

Genetic basis of pregnancy-associated decreased platelet counts and gestational thrombocytopenia

ABSTRACT

Platelet count reduction occurs throughout pregnancy, with 5% to 12% of pregnant women being diagnosed with gestational thrombocytopenia (GT), characterized by a more marked decrease in platelet count during pregnancy. However, the underlying biological mechanism behind these phenomena remains unclear. Here, we used sequencing data from noninvasive prenatal testing of 100 186 Chinese pregnant individuals and conducted, to our knowledge, the hitherto largest-scale genome-wide association studies on platelet counts during 5 periods of pregnancy (the first, second, and third trimesters, delivery, and the postpartum period) as well as 2 GT statuses (GT platelet count < 150 × 109/L and severe GT platelet count < 100 × 109/L). Our analysis revealed 138 genome-wide significant loci, explaining 10.4% to 12.1% of the observed variation. Interestingly, we identified previously unknown changes in genetic effects on platelet counts during pregnancy for variants present in PEAR1 and CBL, with PEAR1 variants specifically associated with a faster decline in platelet counts. Furthermore, we found that variants present in PEAR1 and TUBB1 increased susceptibility to GT and severe GT. Our study provides insight into the genetic basis of platelet counts and GT in pregnancy, highlighting the critical role of PEAR1 in decreasing platelet counts during pregnancy and the occurrence of GT. Those with pregnancies carrying specific variants associated with declining platelet counts may experience a more pronounced decrease, thereby elevating the risk of GT. These findings lay the groundwork for further investigation into the biological mechanisms and causal implications of GT.

Gestational thrombocytopenia: a case-control study of over 3,500 pregnancies

Gestational thrombocytopenia (GT) affects an estimated nine million women annually. Women with GT have recurrent episodes on subsequent pregnancies suggesting that GT is related to a maternal factor rather than a factor unique to the individual pregnancy. We performed a case-control study of over 3 500 pregnancies at a single hospital during 2017. We defined GT as any pregnancy with a platelet count <150 000/µl during the 100 days prior to delivery. We excluded women with platelet counts <50 000/µl or with conditions known to cause thrombocytopenia. GT was present in 12% of pregnancies. The median platelet count at delivery was 134 500/µl in cases versus 208 000/µl in controls, P < 0·0001. During the pregnancy, the platelet count declined 31·8% in cases compared with 18·3% in controls (P < 0·0001) in association with a significant increase in mean platelet volume during each trimester. Among women with GT, platelet counts rapidly increased during the first week postpartum, consistent with a mechanism directly related to high blood flow rates in the gravid uterus. GT, a recurrent condition of at-risk women, is a common haematological disorder of pregnancy. Future research may focus on genetic gain-of-function polymorphisms resulting in increased turnover of platelets uncovered only during periods of high-shear blood flow.

Thrombocytopenia in Pregnancy: Mechanisms and Management

Thrombocytopenia is a common hematologic issue encountered by obstetricians and hematologists, detected in about 10% of all pregnancies. In the vast majority of cases, the thrombocytopenia will be attributed to gestational thrombocytopenia (GT), where the thrombocytopenia is mild, does not necessitate active management, and does not introduce maternal or fetal bleeding risk. Although GT is common, the specific mechanism responsible for it is not known with certainty, and therefore, differentiating it from other causes of thrombocytopenia can be challenging. Previously proposed explanations for GT suggest that a decrease in platelet count is universal in pregnancy, and women diagnosed with GT are simply those with a baseline platelet count on the lower end of normal range. This concept is challenged in this review, and a possible mechanism for GT is proposed. Additionally, a framework for approaching the diagnosis and management of thrombocytopenia in pregnancy is presented.

Platelet reactivity in twin pregnancies

BACKGROUND

Gestational thrombocytopenia is more likely to occur in twin than singleton pregnancies. However, it is unclear whether platelets are more reactive in twin than singleton pregnancies.

METHODS

Changes in spontaneous platelet aggregation and concomitant fall in platelet count were examined over 90min after blood sampling in 171 and 52 citrated whole blood (CWB) samples from 59 and 17 women with singleton and twin pregnancies, respectively. Soluble P-selectin (sP-selectin) levels in the plasma were also determined.

RESULTS

CWB 60min after blood sampling during 2nd trimester exhibited significantly larger numbers of platelet aggregates (1297±1600 vs. 497±432/μl, P=0.040) concomitant with significantly greater net decrease in platelet count (152±55 vs. 115±45×10(9)/μl, P=0.036) in twin than singleton pregnancies, respectively. This was followed by significantly lower 3rd trimester platelet count (181±43 vs. 229±62×10(9)/l, P=0.009) with significantly greater mean platelet volume (8.0±1.2 vs. 7.1±1.1fl, P=0.021) in twin than singleton pregnancies, respectively. The 3rd trimester sP-selectin per platelet was significantly higher in twin than singleton pregnancies.

CONCLUSIONS

Platelets were more reactive in the 2nd trimester of twin than singleton pregnancies. This enhanced platelet reactivity may explain the decreased platelet count in the 3rd trimester of twin pregnancy.

Differentiation of acute fatty liver of pregnancy from syndrome of hemolysis, elevated liver enzymes and low platelet counts

As proposed criteria (Swansea criteria) for the diagnosis of acute fatty liver of pregnancy (AFLP) do not include antithrombin (AT) activity, diagnosis of AFLP may be delayed. The aim of this review is to underscore problems in the differential diagnosis of AFLP and the syndrome of hemolysis, elevated liver enzymes and low platelet counts (HELLP syndrome) and to facilitate prompt diagnosis of AFLP. Published works dealing with liver dysfunction in pregnancy, HELLP syndrome and AFLP were reviewed. AFLP and HELLP syndrome shared common clinical, laboratory, histological and genetic features, and differential diagnosis between them was often difficult. However, HELLP syndrome was likely to occur in patients with hypertension, but AFLP occurred often in the absence of hypertension. In addition, AFLP was exclusively associated with pregnancy-induced antithrombin deficiency (PIATD). Approximately 50% of patients with AFLP did not have thrombocytopenia at presentation. As the Swansea criteria for AFLP did not include PIATD, diagnosis of AFLP was delayed until manifestation of life-threatening complications; 60% of women were admitted to intensive care and 15% to a specialist liver unit. In conclusion, incorporation of AT activity of less than 65% into the diagnostic criteria for AFLP may facilitate suspicion and prompt diagnosis of AFLP, decrease uncertainty regarding the diagnosis of AFLP, and contribute to better investigation and understanding of the process leading to the development of liver dysfunction.

Retrospective audit of outcome of regional anesthesia for delivery in women with thrombocytopenia

Regional anesthesia for pain at delivery in the presence of maternal thrombocytopenia is a clinical dilemma. We reviewed 10,369 obstetric cases (12 months) from our tertiary center. Generally, hemodilution of pregnancy does not result in thrombocyte counts of <150,000/mm(3) at delivery. A total of 166 births (1.6%) were recorded in women with thrombocytes <150,000/mm(3) at delivery. Parturients with >150,000/mm(3) at week 36 were separated post hoc (n=35; 21%) and the remaining parturients were divided as having <100,000/mm(3) (n=30; 18%) or 101,000-150,000/mm(3) (n=101; 60.5%). Epidural or spinal anesthesia was administered to 30% women with <100,000/mm(3) whereas 56% women with >101,000/mm(3) received these options (P=0.003). A total of 13.9% of parturients with trimester-long thrombocytopenia required blood products; 10/23 (43.5%) parturients undergoing cesarean section also required blood products (P=0.000). Four of six babies with Apgar scores of <or=7 at 1-min were born to women with platelets <100,000/mm(3) (P=0.009). There were no statistically significant differences in mean birth weights. Women with thrombocytes <150,000/mm(3) at birth but within the normal range at week 36 were more likely multiparas (P=0.001). We conclude that a difference in maternal and neonatal outcomes exists between mothers who were thrombocytopenic only at delivery compared to those with trimester-long thrombocytopenia, with the latter mothers and babies having more adverse events.

Association of a decrease in antithrombin III activity with a perinatal elevation in aspartate aminotransferase in women with twin pregnancies: relevance to the HELLP syndrome

BACKGROUND/AIMS

Decreased antithrombin III (AT-III) activity and/or thrombocytopenia associated with an elevated serum level of aspartate aminotransferase in late pregnancy can threaten the lives of both the mother and the fetus. We investigated whether antenatal declines in AT-III activity and the platelet count occur in late twin pregnancy and whether reduced AT-III activity and/or thrombocytopenia precedes an increase in the serum level of aspartate aminotransferase.

METHODS

The platelet count, AT-III activity, and the serum level of aspartate aminotransferase were determined weekly or biweekly in 237 women with twin pregnancies in a longitudinal and partly prospective study.

RESULTS

Both AT-III activity and the platelet count decreased gradually in the last month of pregnancy, irrespective of the presence or absence of clinical signs of pre-eclampsia. A perinatal elevation in aspartate aminotransferase occurred in 36 (15%) of 237 women. The risk of a perinatal elevation in aspartate amino-transferase increased as the antenatal AT-III activity and/or the platelet count decreased. Pre-eclampsia developed in 60 women (25%). The relative risk of a perinatal aspartate aminotransferase elevation (95% confidence interval) for the 60 women with pre-eclampsia, the 60 women with a platelet count < or = the 25th percentile (164 x 10(9)/1), and the 60 women with AT-III activity < or = the 25th percentile (76% of normal) was 1.9 (1.0 to 3.4), 4.1 (2.3 to 7.5), and 5.9 (3.2 to 11.1), respectively, compared with the remaining 177 women.

CONCLUSIONS

AT-III activity and platelet count gradually decreased in the last month of twin pregnancies. A perinatal aspartate aminotransferase elevation was preceded by marked decreases in these parameters in women with twin pregnancies. The monitoring of AT-III activity and platelet count in women who exhibit a gradual decline in these parameters may help to avoid the development of severe HELLP syndrome.

Antiplatelet antibody testing in thrombocytopenic pregnant women

OBJECTIVE

The purpose of the study was to attempt to distinguish pregnant women with gestational thrombocytopenia from those with idiopathic immune thrombocytopenia by eight different platelet antibody assays.

STUDY DESIGN

Sera from pregnant women with presumed gestational thrombocytopenia (n = 160) and idiopathic immune thrombocytopenia (n=90) were prospectively tested for indirect and platelet-associated immunoglobulins G and M and complement C3, as well as for serotonin release. After the results were analyzed, a subset of patients were subsequently analyzed for circulating antiplatelet antibody directed against platelet membrane glycoprotein GPIIb/IIIa.

RESULTS

Indirect immunoglobulin G was significantly greater in the 85 women with idiopathic immune thrombocytopenia than in the 129 women with gestational thrombocytopenia (p<0.001). Platelet-associated immunoglobulin G was elevated in the majority of women, both those with gestational thrombocytopenia and those with idiopathic immune thrombocytopenia. There were also no statistically significant difference in the values for platelet-associated C3 or indirect immunoglobulin M and C3. Levels of platelet-associated immunoglobulin M showed a tendency to be higher in women with gestational thrombocytopenia (p=0.04), as did the values in the serotonin release assay (p=0.06).

CONCLUSION

Our data demonstrate that patients with gestational thrombocytopenia had surprisingly high levels of platelet-associated immunoglobulin despite mild thrombocytopenia. Comparison of a relatively large number of patients with idiopathic immune thrombocytopenia and gestational thrombocytopenia indicates that women with idiopathic immune thrombocytopenia cannot be distinguished from those with gestational thrombocytopenia by means of one or more of the prototypic platelet antiglobulin tests currently in use. Our preliminary data with glycoprotein-specific assays indicate that they may be more useful.

Clinical relevance of gestational thrombocytopenia of < 100,000/microliters

We identified 22 women with thrombocytopenia of < 100,000/microliters found incidentally during pregnancy and prospectively monitored their platelet count and clinical outcome for a minimum of 6 months postpartum. During the study period, four women became pregnant twice, accounting for a total of 26 pregnancies. The lowest platelet count during pregnancy was 65,600/microliters +/- 19,400 (mean +/- SD), and at delivery 84,500/microliters +/- 32,300 (P < 0.02). The thrombocytopenia was virtually asymptomatic in all patients during the pregnancy and delivery, whether vaginal or surgical. Neonatal platelet counts (n = 18) were normal (270,700/microliters +/- 69,900), and none of the newborns (n = 24) had a bleeding diathesis. Normalization of the platelet count (i.e., > 150,000/microliters) was documented in 18 patients within 1 month postpartum, in five within 3 months postpartum, and in two as late as 5 months after delivery. One woman did not recover from the thrombocytopenia and eventually developed other stigmata of an autoimmune disease. Long-term follow-up showed recurrence of thrombocytopenia in four patients: three in the context of a subsequent pregnancy and one who developed idiopathic thrombocytopenic purpura. Retrospective analysis of blood counts obtained from 12 previous pregnancies demonstrated thrombocytopenia of a similar degree to the index pregnancy. We conclude that gestational thrombocytopenia of < 100,000/microliters is clinically a benign phenomenon that can recur in subsequent pregnancies and is not accompanied by neonatal thrombocytopenia. In some cases, however, pregnancy-associated thrombocytopenia may be a manifestation of an autoimmune disease with its attendant implications for the neonate. Since the differential diagnosis between the two conditions may be difficult to establish when first encountered during pregnancy, a conservative approach emphasizing careful surveillance and guarded reassurance is justified as long as the platelet counts are > 50,000/microliters.

Maternal and fetal effects of intravenous patient-controlled fentanyl analgesia during labour in a thrombocytopenic parturient

The use of intravenous (i.v.) patient-controlled fentanyl analgesia during labour in a parturient with unexplained thrombocytopenia (70 x 10(3).ml-1) is described. The patient self-administered boluses of 25 micrograms of fentanyl with a lock-out interval of ten min. In addition, a concurrent fentanyl infusion of 25 micrograms.hr-1 was given. Effective analgesia was achieved during labour and a total of 1025 micrograms of fentanyl was infused over 11 hr 55 min until delivery of a vigorous infant with Apgar scores of 9 after one and five min. Respiratory depression or undue sedation were not observed in the mother either during labour or in the post-partum period. At birth, maternal total plasma fentanyl concentration was 1.11 ng.ml-1, whereas neonatal umbilical total plasma fentanyl concentration was 0.43 ng.ml-1. Newborn plasma protein binding of fentanyl was lower compared to the mother (63% vs 89%). Thus, free fentanyl concentrations (0.16 ng.ml-1) were identical in the mother and newborn at delivery.

ITP in pregnancy and the newborn: introduction

Idiopathic thrombocytopenic purpura (ITP) occurs more commonly in young women and is one of the commonest immune mediated disorders in pregnancy. It may exist as an incidental finding in an otherwise healthy pregnant woman or may be associated with symptomatic reduction in the platelet count and varying degrees of clinical hemorrhage. The condition termed incidental thrombocytopenia of pregnancy is invariably associated with a platelet count of greater than 100 x 10(9)/L and a very low incidence of fetal thrombocytopenia. Symptomatic thrombocytopenia is more commonly associated with low platelet counts in the fetus (estimated between 20%-40%). It has recently been suggested that the incidence of fetal thrombocytopenia is substantially lower than this figure. The management of ITP in pregnancy is complicated by the fact that fetal thrombocytopenia is difficult to diagnose and carries substantial risks during the delivery process with rare cases of fetal hemorrhage occurring spontaneously in utero. Unfortunately there are no laboratory studies that can be performed precisely in the mother that may predict the occurrence of fetal thrombocytopenia. Maternal management is usually directed towards treatment of maternal symptoms. Maternal treatment or response to treatment is inconsistently associated with predictable changes in the fetal platelet count. Obstetric management is aimed at reducing the risks of life threatening fetal hemorrhage occurring at the time of delivery, and fetal management is directed towards the obtaining of fetal platelet samples in order to plan an appropriate strategy for obstetrical delivery. Fetal blood samples are obtained either by a scalp vein puncture at the time of delivery or earlier in gestation by the use of the newer technique termed percutaneous umbilical blood sampling. Fetuses with platelet counts of less then 50 x 10(9)/L are generally delivered by cesarean section whereas those with counts greater than 50 x 10(9)/L are allowed to proceed with vaginal delivery assuming no obstetrical contraindications exist. The use of IVIgG therapy during pregnancy has theoretical implications on improving platelet counts in the mother in situations of severe hemorrhage, however cannot be considered to be appropriate treatment for the prevention of fetal thrombocytopenia, since the exogenous transport of IVIgG across the placenta appears to be inconsistent and unpredictable.(ABSTRACT TRUNCATED AT 400 WORDS)

Incidentally detected thrombocytopenia in healthy mothers and their infants

The unexpected discovery of thrombocytopenia in an asymptomatic pregnant woman--often considered to be equivalent to the diagnosis of idiopathic thrombocytopenic purpura--leads to a variety of interventions, including delivery by cesarean section. However, the actual risk to mothers and their infants posed by incidentally noted thrombocytopenia is not known. To investigate this issue, we performed a prospective study of a group of normal women who delivered at our medical center and their infants during a period of one year. Of the 2263 women who delivered during the year, 1357 were considered to be normal. One hundred twelve of the women (8.3 percent) had mild thrombocytopenia (range of platelet counts, 97 to 150 x 10(9) per liter). The thrombocytopenia had no discernible clinical effect on the women or their infants. The frequency of thrombocytopenia in babies born to this group of women was not appreciably different from that in babies born to the other normal patients who did not have thrombocytopenia, and none of the infants of women with thrombocytopenia had a platelet count of less than 100 x 10(9) per liter. This study demonstrates that the frequency of mild thrombocytopenia is high in normal pregnant women at term and that the thrombocytopenia appears to have no adverse effect on either the mothers or their infants. To perform obstetrical interventions such as cesarean section because of thrombocytopenia in these mothers is not justified.