Changes in haemostasis during normal pregnancy

OBJECTIVES: (1) To study the changes in the haemostatic variables during normal pregnancy, and (2) to compare them with the corresponding variables in a control group of nonpregnant women. SETTING: University Hospital. SUBJECTS: The study involves two groups of women: pregnant women (in 35th-40th gestational weeks (GW)) (N = 35) and a control group of nonpregnant women (N = 35). METHODS: We examined the global tests, the variables relating to coagulation and fibrinolysis and the group of natural inhibitors of coagulation, and compared them between the two groups. RESULTS: The pregnant women had statistically significantly higher values for: prothrombin time (PT) (P < 0.0001), thrombin time (TT) (P < 0.0001), fibrinogen (P < 0.0001), activity of factor VII (P < 0.0001), factor X (P < 0.0001) and alpha2-antiplasmin (P < 0.002), plasma concentration of D-dimer (plsDD) (P < 0.0001) and activity of heparin cofactor II (HCII) (P < 0.002). They had statistically significantly lower activity of protein C (PrC) (P < 0.0001) and of total protein S (TPrS) (P < 0.0001). CONCLUSION: During normal pregnancy the activation of coagulation is counterbalanced by the activation of fibrinolysis, which maintains the haemostatic balance.     

Changes in plasma adenosine concentrations during normal pregnancy

The aim of this study was to measure changes in plasma adenosine concentration [ADO] during a normal pregnancy and to evaluate the possible role of platelets and red blood cells (RBC) as causes of changes in plasma [ADO]. We measured the plasma [ADO] in normal pregnant women (n = 11) during the first, second and third trimesters. The mean plasma [ADO] in the third trimester was 0.41 +/- 0.08 microM (means +/- SEM), significantly higher than in the first and second trimesters (p < 0.05). In pregnant women, platelet and RBC counts, hematocrit and hemoglobin concentration decreased slightly throughout the pregnancy. The elevation in the plasma [ADO] correlated inversely with the platelet count (r = -0.43, p < 0.05). These results suggest that an increase in the plasma [ADO] in the third trimester may be attributed to the enhanced adenosine release from activated platelets.     

Changes in the subsystems of haemostasis during normal pregnancy

Haemostasis is complex, dynamic and self-regulated system; the maintenance of this balanced equilibrium is achieved by complex regulation between coagulation (pro- and anticoagualants) and fibrinolysis (pro- and antifibrinolytics). During normal pregnancy the cganges in haemostasis are complex, inspite of that the haemostatic balance is preserved and the ratio coagulation/fibrinolysis remains constant. Despite marked changes in the different subsustems of haemostasis and the dominant procoagulant effects, the incidence of VTE remains relatively small.     

Blood pressure and renal function during normal pregnancy

In order to obtain reference values during normal pregnancy 24 women with strict criteria for health and normal pregnancy were studied. Greatest interest was focused on blood pressure (BP) measurements and renal function tests. Investigations were made in early second trimester and in the 30th, 33rd and 36th gestational weeks. Gestational age was estimated by ultrasound measurement of crown-rump length before the 14th gestational week. Both systolic and diastolic BP measured in the right arm were about 10 mmHg lower in the left lateral position than when supine or standing. The difference is suggested to be dependent on hydrostatic factors. Diastolic BP should be defined at the fourth phase of the Korotkoff sounds in order to be reliable because of the common phenomenon of late or non-disappearance of the sounds during pregnancy. Diastolic BP in phase IV increased in up to 25% of the cases with 15 mmHg or more from early second trimester to the 36th gestational week in all three positions. Serum creatinine concentration was low in early second trimester and did not change during pregnancy, while serum urea decreased and serum urate increased during pregnancy. The results emphasize the importance of using reference values from a normal pregnant population obtained at different gestational weeks for comparison in studies on certain pathological conditions during pregnancy, especially pre-eclampsia.     

Clinical signs of normal plasma volume expansion during pregnancy

A majority of cases of pregnancy complications are associated with a relative maternal hypovolemia. The records of 200 pregnant women who had plasma volume determinations were reviewed in hopes of finding indicators of relative maternal hypovolemia other than the pregnancy complication itself. The signs of relative hypovolemia in pregnant women include those of decreased uterine growth, absence of a maternal systolic flow murmur, and absence of significant dependent ankle edema. Laboratory tests indicative of maternal hypovolemia include failure to develop a decline in maternal hematocrit, serum blood urea nitrogen/creatinine ratio > 15, a decreased creatinine clearance, abnormal platelet function, elevated serum glutamic oxaloacetic transaminase, ultrasonic evidence of oligohydramnios and/or decreased maternal heart size, and absence of hypervolemia on chest x-ray film. These findings and tests are only relative indicators of maternal hypovolemia, and it is suggested that, for an accurate defining of pregnant women who are at risk, the actual plasma volume determination has to be performed frequently in the pregnant population.     

Changes in 24-hour heart rate variability during normal pregnancy

OBJECTIVE: We studied the effects of normal pregnancy on heart rate variability as a noninvasive index of maternal cardiovascular autonomic modulation. STUDY DESIGN: Twenty-four-hour Holter recordings were obtained for 8 healthy pregnant volunteers during early pregnancy (相似文献   

Changes in serum immunoreactive erythropoietin during the menstrual cycle and normal pregnancy

Immunoreactive erythropoietin was estimated in samples of serum collected during the follicular and luteal phases of the menstrual cycle in seven women and in sera collected sequentially throughout normal pregnancy in these and three other women. Estimates of serum erythropoietin during the follicular and luteal phases of the menstrual cycle were almost identical. During pregnancy in all 10 subjects serum erythropoietin increased at some time after 8 weeks gestation. These changes were not related to other endocrine values, to indicators of haematological and renal function or to infant birthweight except that changes in serum erythropoietin and placental lactogen were related (P less than 0.00001). In one other woman treated over 17 weeks of pregnancy with continuous intravenous infusion of salbutamol, erythropoietin levels were within the range found in normal pregnancies.     

Changes in serum immunoreactive erythropoietin during the menstrual cycle and normal pregnancy

Summary. Immunoreactive erythropoietin was estimated in samples of serum collected during the follicular and luteal phases of the menstrual cycle in seven women and in sera collected sequentially throughout normal pregnancy in these and three other women. Estimates of serum erythropoietin during the follicular and luteal phases of the menstrual cycle were almost identical. During pregnancy in all 10 subjects serum erythropoietin increased at some time after 8 weeks gestation. These changes were not related to other endocrine values, to indicators of haematological and renal function or to infant birthweight except that changes in serum erythropoietin and placental lactogen were related ( P < 0.00001). In one other woman treated over 17 weeks of pregnancy with continuous intravenous infusion of salbutamol, erythropoietin levels were within the range found in normal pregnancies.     

Changes in erythrocyte volume and shape in pregnancy

Summary. Erythrocyte measurements were made in groups of women in pregnancy and the early puerperium and were compared with those of non-pregnant women. The mean cell volume rises in pregnancy and this persists in the early puerperium, although declining, while the erythrocyte becomes more spherical with a decreasing diameter and increasing thickness. The diameter and thickness changes revert to the non-pregnant values by the early puerperium.     

Dyspnoea during normal pregnancy

The incidence, severity and time-course of dyspnoea were assessed in 62 women on eight occasions throughout a normal pregnancy. Fifteen per cent of subjects noticed an increase in dyspnoea in the first trimester compared with the nonpregnant state and in almost half of them dyspnoea was experienced before 19 weeks gestation; 76% complained of this symptom by 31 weeks gestation. After this time, few subjects noticed any increase in their symptoms.     

Smoking and its effect on maternal plasma volume during and after normal pregnancy

Smoking during pregnancy decreases birthweight significantly. The mechanisms causing this decrease have not yet been clarified. Plasma volume (expansion) is positively related to birthweight. There are indications that plasma volume expansion in pregnancy is lower among smokers. A group of healthy women (n = 70) producing healthy mature babies after an uncomplicated pregnancy was studied. No difference in plasma volume was observed between non-smokers and smokers during and after pregnancy. It is unlikely that the growth-depressing effect of smoking during pregnancy is mediated by an influence on plasma volume expansion.     

Three-dimensional sonographic measurement of normal fetal brain volume during the second half of pregnancy

OBJECTIVES: This study was undertaken to develop a three-dimensional (3D) ultrasound method of measuring fetal brain volume. STUDY DESIGN: Serial 3D sonographic measurements of fetal brain volume were made in 68 normal singleton pregnancies at 18 to 34 weeks of gestation. A comparison was made with fetal brain volume estimates from two-dimensional (2D) sonographic measurement of head circumference and published postmortem fetal brain weights. RESULTS: Coefficient of variation for fetal brain volume (3D) caused by differences between repeated tests was 10.2% and between analyses of the same recorded volume 2.2%. Median brain volume increases from 34 mL at 18 weeks to 316 mL at 34 weeks. Median brain weight represented approximately 15% of total fetal weight. The 3D ultrasound-derived brain weight is larger than postmortem brain weight. However, this is not so for brain weight derived from total fetal weight at autopsy. A good agreement between 3D and 2D brain volume was found. CONCLUSION: Sonographic measurement of fetal brain volume demonstrated an acceptable intraobserver variability and a nearly 10-fold increase during the second half of gestation.     

Fibrinopeptide A during normal pregnancy

Fibrinopeptide A (FPA) is the first peptide released from fibrinogen upon thrombin action. Plasma FPA is cleared rapidly with a first order kinetics and therefore its level reflects the rate of thrombin cleavage of fibrinogen. A prospective study was undertaken to establish normal values of FPA during pregnancy. The mean FPA for the pregnant group (n = 136) was 2.8 ng/ml (SD = 3.3) while it was 1.24 ng/ml (SD = 0.4) for a nonpregnant control group of healthy women (n = 30). The median FPA for the pregnant group was 2.2 ng/ml and 1.4 ng/ml for the nonpregnant group (Wilcoxon test P less than 0.0001). Plasma FPA levels increased with gestational age. The median value was 1.5 ng/ml in the first trimester (n = 18), 1.8 ng/ml in the second trimester (n = 40), and 2.5 ng/ml in the third trimester (n = 78). Plasma FPA concentrations in the third trimester were significantly higher than in the first and second trimester. These findings suggest increased thrombin activity and fibrin generation during the course of normal pregnancy.