First line coagulation test in 3rd trimester pregnant women and related factors

1. Introduction

According to a report by the World Health Organization, postpartum bleeding is still the leading cause of death for pregnant women [9]. Therefore, timely and appropriate detection of hematological changes in general and blood coagulation in particular in obstetrics is a research direction of current interest. In the world, there have been many studies on blood coagulation characteristics in pregnant women such as: Boehlen F and CS [3], Cerneca F, Ricci G, Simeone R [4], ... In 2011, our research group took the step first learned about this issue in pregnant women in the first three months of pregnancy in Hanoi [1]. However, in Vietnam, not many authors have paid attention to changes in the blood coagulation system during pregnancy. To contribute to understanding this issue, we conduct research with the following objectives:

1. Describe first line coagulation test in 3^rd trimester pregnant women,
2. Determine factor(s) related to the first line coagulation test in 3^rd trimester pregnant women.

2. Subjects and method

2.1. Subjects:

• 254 women in their last trimester of pregnancy (30 weeks or more) came for regular prenatal check-ups at Hanoi Obstetrics Hospital since September 2012 and volunteered to participate in the study.
• 50 healthy women of childbearing age (15-49 years old) but not pregnant were recruited into the control group.

2.2. Study indexes:

• Clinical: Mother's age, height, weight, gestational age.
• Blood coagulation: Platelet count, PT, APTT, Fibrinogen.

2.3. Equipments:

• Automatic cell counter XT 1800i from Sysmex Japan.
• CA 1500 coagulation machine from Sysmex Japan.

2.4. Method. Pregnant women > 30 weeks pregnant, after agreeing to participate in the study, will answer the personal information collection form, then have their blood drawn at the Laboratory Department of Hanoi Obstetrics and Gynecology Hospital: one tube of blood will be tested. Cell test, a tube of blood for coagulation tests. Testing techniques are performed in accordance with the procedures currently applied at the Department of Hematology and Blood Transfusion at Bach Mai Hospital.

2.5. Data analysis. Collected data were analyzed using Stata 10.0 software.

2.6. Ethical Aspects. Pregnant women agreed to participate in the study. The results are completely confidential and are only used for research purposes, contributing to pregnant women's care during pregnancy.

3. Results

3.1. Characteristics of basic coagulation tests in pregnant women in the third trimester.

Table 1

Blood coagulation test results

Comment: Table 1 shows that all indicators had significant changes compared to the control group in which the platelet count decreased (p<0.01), PT and aPTT decreased (p<0.05), while fibrinogen increased (p<0.001) when using the t-student test.

Table 2

Results of coagulation tests according to gestational age

Comment: Table 2 shows that the number of platelets gradually decreases with gestational age. Plasma fibrinogen concentration increased with gestational age with statistical significance (ANOVA test).

3.2. Some factors related to blood coagulation tests in pregnant women in the third trimester.

Looking for some factors related to the two first-round coagulation test indexes that had the most obvious changes in the research group, platelet count and fibrinogen, we found that in the research indexes, there was no index. Which is related to changes in platelet count? Plasma fibrinogen concentration had a weak correlation with BMI of study subjects when using Pearson:

The correlation coefficient is 0.2799, which is statistically significant through verification by pair-wise correlation test.

Once we have determined the correlation between fibrinogen and BMI, we want to build a linear regression model showing the association between fibrinogen and BMI.

So, we can write the equation as follows:

Fibrinogen = 3.11 + 0.035 x BMI

4. Discussion.

During pregnancy, platelet counts often decrease slightly, often due to dilution or increased platelet consumption [2]. Our results are also consistent with Liu XH and CS [7] and Boehler F and CS [3]. The platelet count in pregnancy has been reported to begin to decrease from the first trimester [1]. Thrombocytopenia usually begins in the second trimester of pregnancy and is only mild or moderate [4].

In this study, APTTs were shortened compared to the control group, suggesting increased activation of the endogenous coagulation pathway. This result is also consistent with other authors [1, 7]. These indicators show a tendency to increase coagulation in pregnant women to prepare for the risk of blood loss during childbirth [5, 10]. The PTs index also shortened with statistical significance compared to the control group, while in research in the first trimester, this change tends to appear without a statistically significant difference [9]. Are the factors involved in the extrinsic coagulation pathway changing later than the intrinsic pathway?

The higher fibrinogen concentration in pregnant women compared to the control group is also consistent with our previous results when studying in the first trimester [1]. This result is consistent with the trend of gradually increasing plasma fibrinogen concentration during pregnancy that Cerneca F [4] noted.

The hypercoagulable tendency in pregnant women is expressed in both an increase in coagulation factors and fibrinogen, and a decrease in anticoagulant factors, this combination becomes a favorable factor for the formation of venous thrombosis [ten]. Among 33 pregnant women who died related to venous thromboembolism, William M's group of authors found that 18 pregnant women were classified as obese [10]. Michael Beckman's research group found that the plasma fibrinogen concentration of pregnant women with BMI > 30 was significantly higher than the group of pregnant women with BMI < 30. These authors noted an average correlation between fibrinogen and BMI of pregnant women in the last trimester (r = 0.4) as well as the increase in fibrinogen concentration according to the level of obesity [8]. Previous studies have also shown that obesity increases the risk of venous thromboembolism 4-5 times compared to normal [6], [10]. Our results also recorded a statistically significant correlation between fibrinogen and BMI of pregnant women and built a linear regression equation between these two quantities. This result allows prediction of fibrinogen concentration based on pregnant women's BMI, and also warns pregnant women to maintain an appropriate weight gain to limit the risk of thrombosis that can lead to dangerous complications, for mothers and fetuses.

5. Conclusion.

1. Characteristics of basic coagulation tests in third-trimester pregnant women show a tendency for increased coagulation compared to the control group.
2. Factors related to coagulation test index in pregnant women in the third trimester. Linear regression equation between fibrinogen and BMI: Fibrinogen = 3.11 + 0.035xBMI.