Platelets and pregnancy

Platelet activation in pregnancy-induced hypertension

BACKGROUND

Although excess platelet activation, as indicated by increased plasma beta thromboglobulin (beta-TG), has been shown in pregnancy-induced hypertension (PIH), platelet adhesion, platelet morphology and a comparison of platelet and soluble (plasma) levels of the adhesion molecules P-selectin (pPsel and sPsel, respectively) have not been studied.

METHODS

We conducted a cross-sectional study of 35 consecutive women with PIH (age 31+/-6 years), 31 consecutive women with normotensive pregnancies (age 29+/-5 years) and 30 normotensive non pregnant women (age 30+/-5 years). Platelet adhesion was studied in vitro by binding to fibrinogen-coated microwells, platelet morphology [mass and volume by flow cytometry], whole-platelet P-selectin (pPsel) by ELISA of the lysate of 2 x 10(8) cells, and the plasma markers soluble P-selectin (sP-sel) and beta-TG, by ELISA.

RESULTS

The women with PIH had significantly raised sPsel, pPsel and (as expected) beta-TG (all p<0.05), when compared to the normotensive pregnant women and controls. However, in PIH platelet adhesion was similar to that in the normotensive pregnancy, but still higher than the normal controls (p<0.001). There was no difference among the three groups with respect to platelet mass and volume. pPsel and platelet adhesion correlated with gestational age and with systolic and diastolic blood pressure (all p<0.05).

CONCLUSIONS

Increased platelet activation and adhesion develop during normal pregnancy, with some indices being further altered in PIH.

Immune thrombocytopenic purpura in pregnancy

Of all pregnant women 1.2% have platelet counts below 100 x 10(9)/l. Only a small proportion of these have immune thrombocytopenic purpura (ITP). ITP is caused by antibodies directed against one's own platelets and may affect the mother as well as the fetus. No cases with documented intrauterine fetal bleeding have been reported. The most critical time for the fetus is usually a few days after birth. Hitherto the patient's history has been the best predictor of maternal and neonatal complications. Diagnostic cordocentesis entails a considerable risk and is to be discouraged in most situations. Intrauterine transfusions are effective only for a very limited period. There is no evidence that caesarean section protects the thrombocytopenic infant from intracranial haemorrhage. We therefore recommend restricting caesarean section to obstetric indications and to situations with proven fetal thrombocytopenia and enhanced obstetric risk. The safe cut-off level has yet to be ascertained. It is mandatory to control the newborn's platelet count during the first three days of life.

Intravenous immunoglobulin treatment in hematological diseases

In the last decade large amounts of intravenous immunoglobulin (i.v.Ig) have been used worldwide. Doubts exist as to whether this increased use is paralleled by a comparable growth of reliable data on the therapeutic effectiveness of i.v.Ig. We performed a literature search using MEDLINE from January 1981 to January 1997 and analysed articles on the use of i.v.Ig in hematological disorders and searched for published guidelines. For most hematological disorders, evidence to use i.v.Ig as first line therapy is not very strong. For many disorders no controlled trials have been performed. In published guidelines, i.v.Ig is only recommended, with a few exceptions, when other treatments have failed or are contraindicated. Therefore the increase of consumption of i.v.Ig can not be explained by an increase in established indications in hematology.

Platelet and hemorrhagic disorders associated with pregnancy: a review. Part I

Disorders of coagulation remain an important potential cause of maternal morbidity and mortality. Bleeding disorders in pregnancy, unlike disorders of hypercoagulability, most often can have little impact on the mother but devastating consequences for the fetus. Further complicating the issue is that not all disorders of coagulation are inherited. Some are due to maternal illnesses unique to pregnancy, others are due to drug ingestion, and yet others remain idiopathic. In still other instances, thrombocytopenia is a minor consequence of a more severe disorder and will resolve when the inciting agent is removed or treated. A basic understanding of the pathophysiology of various conditions that lead to bleeding diathesis in pregnancy is necessary in order to effectively manage these varied clinical disorders. In addition, knowledge of whether the major morbidity is fetal or maternal or both can impact management. This review is concerned with the etiology, pathophysiology, diagnosis, and general management of commonly encountered disorders in pregnancy that place the mother and fetus at increased morbidity and mortality because of the potential for hemorrhage. Acutely acquired disorders and the resultant maternal manifestation versus a chronic disease process that is altered by the state of pregnancy are distinguished. Where possible, the incidence and prognosis of the disorder are provided. Actual cases are included to illustrate how similar presentations of distinctly different disorders can confuse and complicate an accurate diagnosis that is essential for appropriate management.

Fetal/neonatal alloimmune thrombocytopenia: a continuing challenge

Fetal/neonatal alloimmune thrombocytopenia is the platelet counterpart of the red cell disorder, haemolytic disease of the fetus and newborn. Unlike Rhesus pregnancies, first pregnancy is commonly affected. It is a progressive disease and can cause severe fetal damage, late fetal and neonatal loss and severe handicap. No screening programme is currently available and the diagnosis is often delayed. Testing for platelet antibodies in those mothers whose babies are thrombocytopaenic is necessary for early detection of this condition.

Thrombocytopenia in pregnant women who use cocaine

OBJECTIVE

Our purpose was to determine the prevalence of cocaine-associated thrombocytopenia.

STUDY DESIGN

This cohort study was conducted in an inner-city prenatal center. A total of 1907 patients were screened by the Mother's Project, which is an intervention project for inner-city cocaine-abusing parturients. Platelet counts were grouped by illicit drug usage.

RESULTS

Platelet counts were available in 37% (709) of subjects; there were no differences between subjects with available platelet counts and those without on illicit drug use or other demographic measures. Five groups were defined: drug-free group (n = 331), cocaine group (n = 104), cocaine and opiates group (n = 11), opiates group (n = 18), and other-drug group (n = 236). Nineteen subjects had a low platelet count (< 150 x 10(9)/L). The medical records of all subjects with a low platelet count were reviewed for any medical condition known to be associated with thrombocytopenia, and two subjects were excluded. The rate of thrombocytopenia in the drug-free group was 1.5%, whereas the rate in the cocaine group was 6.7% (relative risk 4.4, p < 0.05). Because of the reported association of thrombocytopenia with seropositive human immunodeficiency virus status, seropositive women were excluded from the analysis. Even after human immunodeficiency virus status adjustments for the estimated rate, the cocaine-using group continued to have a significantly higher rate of thrombocytopenia (5.4% to 7.2% vs 1.23% to 1.26%, p < 0.05 to p < 0.005).

CONCLUSIONS

These results indicate that cocaine use is an independent risk factor for thrombocytopenia in an inner-city parturient population.

Fetal and neonatal thrombocytopenia

Thrombocytopenia is defined as platelet count less than 150,000 plat/mm3. Etiologic factors involved include immunological (NAIT and ITP), fetal infectious disease, chromosomal and nonchromosomal, and miscellaneous causes. While the understanding of fetal thrombocytopenia is driven by reason to do fetal blood sampling, discovery of neonatal thrombocytopenia is driven by blood counts performed because of the risk of infections. The most serious consequence of thrombocytopenia in the fetus/neonate is intracranial hemorrhage which can occur in utero as early as 18 weeks gestation. The key factor in perinatal prevention of intracranial hemorrhage is early diagnosis and treatment, possibly in utero. Cordocentesis under direct ultrasound guidance and platelet transfusions have played a major role in the management of fetal/neonatal thrombocytopenia. Ongoing studies and high resolution ultrasound will continue to explore and hopefully clarify fetal and neonatal thrombocytopenia and facilitate recognition of primary and secondary thrombocytopenias.