The platelet count in pregnancy

Platelet counts in women with normal pregnancies: A systematic review

The occurrence of thrombocytopenia in 5% of pregnant women at delivery, described as gestational thrombocytopenia, is well documented. A commonly believed concept is that gestational thrombocytopenia is the result of gradually decreasing platelet counts in all women during pregnancy. The goal of our study was to evaluate the data supporting this concept. To learn what is known about platelet counts throughout normal pregnancies, we systematically reviewed all publications describing platelet counts during pregnancy. We identified 3,039 studies; 46 reporting ≥30 women with normal pregnancies were included in our analyses. The combined mean platelet counts from all studies supported the concept that platelet counts decrease during pregnancy and increase postpartum: first trimester, 251,000/µL (95% CI, 238,000-264,000/µL); second trimester, 238,000/µL (95% CI, 222,000-253,000/µL); third trimester, 224,000/µL (95% CI, 213,000-235,000/µL); delivery, 237,000/µL (95% CI, 209,000-264,000/µL); 4-8 weeks postpartum, 247,000/µL (95% CI, 207,000-287,000/µL). However, individual studies were inconsistent. Eleven longitudinal studies compared platelet counts on the same women at different times during gestation: seven reported a decrease; four reported no change. Ten cross-sectional studies compared platelet counts of different women at different times during gestation: five reported a decrease; five reported no change. Five studies compared platelet counts of pregnant to nonpregnant women: three reported that platelet counts were lower in pregnant women; one reported no difference; one reported that platelet counts were higher in pregnant women. These inconsistent data emphasize the need to accurately describe platelet counts throughout normal pregnancies. Accurate data are essential for evaluating the clinical importance of thrombocytopenia during pregnancy.

Changes in blood parameters in New Zealand White rabbits during pregnancy

Changes in clinical pathology parameters, particularly those related to blood coagulation, were examined throughout the gestation period in New Zealand White rabbits. As compared with the non-pregnant group, the following major changes were observed in the pregnant group. For blood coagulation-related parameters, platelets increased progressively and fibrinogen increased slightly from organogenesis, prothrombin time was significantly prolonged during organogenesis and shortened in the late fetal growth stage, activated partial thromboplastin time was significantly prolonged during the fetal growth stage, and antithrombin III increased during and after late organogenesis. Such changes in blood coagulation-related parameters during the later stages of gestation seem to be physiological responses in preparation for protecting against excessive haemorrhage or haemostasis at parturition. For the other haematological and blood chemical parameters as well as progesterone, red blood cell counts, haemoglobin and haematocrit began to decrease during organogenesis and continued to decrease thereafter. Reticulocyte counts significantly increased during organogenesis and decreased thereafter. White blood cell parameters, except for neutrophils, showed significant decreases during the fetal growth stage. Serum progesterone concentration reached its highest level early in organogenesis and decreased thereafter. Total protein, albumin, glucose, cholesterol, calcium, blood urea nitrogen and creatinine decreased significantly during the middle and/or late periods of gestation. In conclusion, the data obtained from the present study can be used as background data for effective evaluation of reproductive toxicology in rabbits, and pregnant rabbits may serve as models of pregnant women in research pertaining to clinical pathology and gestation.

Immune thrombocytopenia in pregnancy

Autoimmune thrombocytopenia (ITP)

1) The risks to mother and fetus have previously been overstated.

2) There is no maternal test which will accurately determine fetal thrombocytopenia.

3) The only reliable test for fetal thrombocytopenia is cordocentesis – this carries a higher morbidity than that of fetal intracerebral haemorrhage from ITP.

4) Contrary to received wisdom, there is no evidence that, even for the most severely thrombocytopenic infant, abdominal delivery protects against intracranial haemorrhage.

5) Management therefore involves keeping the maternal platelet count above 50 × 1091 and choosing the route of delivery on normal obstetric grounds.

Alloimmune thrombocytopenia

1) Alloimmune thrombocytopenia is commoner than hitherto believed (0.15% all neonates).

2) The fetal risks are considerable: intracranial haemorrhage occurs in 4% of cases antenatally and in 10% in labour. The risks are virtually confined to those with a platelet count of less than 30 × 109l−1.

3) Cordocentesis is justified for the ‘at risk’ fetus; fetal immunoglobulin or platelet therapy can be given.

4) When the fetal platelet count is below 50 × 109l−1, abdominal delivery should be planned.

5) A maternal screening test for neonatal alloimmune thrombocytopenia exists (lack of P1A1 antigen).

Changes in clinical pathology parameters during gestation in the New Zealand white rabbit

Hematology and serum chemistry parameters were analyzed in 2 groups of pregnant rabbits to assess changes in these parameters over the course of gestation. These data were used to generate a historical control reference range for embryofetal development regulatory toxicology studies. During the 28-day gestation period, the following major changes were observed. Red blood cell counts, hemoglobin, and hematocrit increased slightly up to day 13 and subsequently decreased progressively to a nadir for all parameters on day 25. Reticulocyte counts increased maximally by day 16 and then decreased to a minimum value on day 28. White blood cell counts progressively declined after day 7. Platelet counts increased slightly by day 10, were relatively stable until day 13, then progressively decreased to a nadir on day 25. Aspartate aminotransferase and alanine aminotransferease values increased steadily throughout the study to reach a maximum value on day 25. Triglycerides increased to their maximum value by day 19 and then steadily decreased until day 28, whereas cholesterol decreased progressively to reach a nadir on day 25. Urea and total protein decreased steadily from day 13 onward. Calcium values decreased throughout the study to reach a minimum value on day 28. Phosphorus values increased slightly on days 7 and 13 and then progressively decreased to reach a nadir on day 28. With a few exceptions, changes that occur in clinical pathology parameters during pregnancy in the rabbit are similar to those observed in pregnant women. Therefore, the rabbit can be considered a suitable species for embryofetal development toxicity studies with regard to clinical pathology.

Prevalence of coagulation abnormalities associated with intrauterine fetal death

PURPOSE

The purpose of this study was to determine factors associated with abnormal coagulation in the setting of intrauterine fetal death (IUFD).

METHODS

We reviewed the charts of 238 patients diagnosed with IUFD over ten years. Data included demographics, co-existing obstetric disease and coagulation studies. A coagulation score was assigned based on the platelet count, prothrombin time, activated partial thromboplastin time and plasma fibrinogen concentration. Approximately 90% of the study population had coagulation scores < 4. A score of > or = 4 was considered abnormal.

RESULTS

Complete coagulation analysis was available in 183/238 patients (77%) within 24 hr of delivery. One hundred and sixty-four of these (89.6%) had a coagulation score, < 4 and 19 had a score > or = 4 (10.4%). No relationship between the coagulation score and age, parity, gestational age at delivery, and number of days the dead fetus remained in utero was found. A coagulation score > = or 4 was associated with the presence of a pregnancy-related disease (P < 0.05), notably abruption (P < 0.001) and uterine perforation (P < 0.05). Four patients without co-existing disease (3.2%), had a coagulation score > or = 4.

CONCLUSION

In most pregnancies complicated by fetal demise, the fetus and placenta are delivered within one week of fetal demise. The previously reported severe coagulation disturbances are largely eliminated by early delivery. Our study shows that coagulation abnormalities occur in some patients with uncomplicated IUFDs (3.2%) and that this number rises in the presence of abruption or uterine perforation.

Gender differences in platelet count and its association with cigarette smoking in a large cohort in Israel

Cigarette smoking has an effect on platelet function and aggregation although the sensitivity of platelet count in reflecting this phenomenon is not known. The association of platelet count with smoking habits was examined in a cohort of 5017 Israeli industrial workers aged 20-64 years. Males had a significantly lower age-adjusted mean platelet count than females (225,600 vs 247,800/microliters; p less than 0.001). Female smokers had lower platelet counts than non-smokers (231,000 for heavy vs 252,000 for never smokers) with a strong dose-response relationship (p less than 0.0001), whereas among males platelet count was slightly higher in smokers (224,000 for non-smokers vs 227,000 for heavy smokers; p = 0.243). The difference in platelet count between the sexes remained almost identical after controlling for smoking status and hematocrit. In multiple regression analysis, the negative association between smoking and platelet count in women remained highly significant (p less than 0.001) after controlling for ethnic origin, alcohol consumption, body mass, hematocrit, cholesterol and HDL-cholesterol, whereas for males the slight positive association was not significant. The reduced platelet count observed in males compared with females and in female smokers, suggests that platelet count may reflect sex differences in hemostasis and the effects of smoking on the hemostatic system. This may have implications for the mechanisms underlying the pathogenesis of ischemic heart disease and should be explored further.

Longitudinal study of platelet indices during normal pregnancy

The purpose of this longitudinal, prospective study was to define platelet indices during normal pregnancy and to compare them to normal nonpregnant values. Indices evaluated included platelet count, mean platelet volume, and platelet distribution width. No significant change occurred in the mean platelet count or mean platelet volume from the second to the third trimester; however, platelet distribution width increased progressively and significantly during this interval (p less than 0.0001). Mean platelet volume versus platelet count showed a significant inverse relationship (p less than 0.0001) and was congruent with normal nonpregnant values. Mean platelet volume versus platelet distribution width exhibited a significant direct relationship (p less than 0.03) that differed remarkably from normal nonpregnant values. These data support the concept of normal pregnancy as a compensated state of progressive platelet consumption. These findings may have important diagnostic and prognostic applications in discerning acute states of platelet consumption superimposed on the compensated consumption of normal pregnancy.

Platelet values during normal pregnancy

Blood samples were obtained from 26 healthy women at regular intervals throughout pregnancy and analysed using a Coulter Counter Model S Plus III. The mean values for the various haematological indices at each stage of gestation were first calculated; the platelet count showed a small decrease throughout pregnancy as did haemoglobin concentration while there was an apparent increase in mean platelet volume, platelet distribution width and white cell count. However, analysis of the trends within patients did not always reflect these mean changes; there was considerable variation in platelet count within individuals and the apparent fall in the group as a whole was accounted for by a considerable fall in a few individuals. The assumption that the trends in platelet values determined from groups of patients will indicate how individual pregnant women behave is misleading.

Early platelet consumption in pre-eclampsia

One hundred and thirty-one women with chronic hypertension were studied serially during pregnancy to determine the sequence of events in the development of superimposed pre-eclampsia and to discover the time of onset. Twenty-seven women developed a sustained rise in plasma urate concentrations, which began at about 28 weeks' gestation and which is characteristic of pre-eclampsia. The mean platelet count was already significantly reduced and continued to fall until delivery, which was on average at 36 weeks' gestation. A comparable but smaller decrease in platelet count was seen in 55 women who had borderline but consistent increases in plasma urate concentrations. In 49 women whose plasma urate concentrations remained steady the platelet count did not change significantly before delivery. The reduced platelet count in women who develop pre-eclampsia suggests that increased platelet consumption is an early feature of the disorder.