Blood Clotting and Pregnancy

While pregnant, a person’s risk for blood clots in their veins (venous thromboembolism) increases 5- to 6-fold. In addition to being a health risk to the mother, the potential for blood clots in the placenta can increase the likelihood of pregnancy loss.

Three main blood clotting measurements are included in the IRMA reproductive immunology assessment. PT, aPTT and INR are all different measures of a person’s blood clotting reaction. If a patient’s blood clots too quickly, it could indicate an increased risk of thrombosis.

Prothrombin time (PT)

Prothrombin time measures how quickly a patient’s blood clots when exposed to an injury like a cut. This is measured in seconds, and the average is around 10 to 13 seconds. When the PT is higher, it means that the blood takes longer to form a clot than is typical. A lower PT value indicates that the blood clots quicker than is typical.

International normalized ratio (INR)

International normalized ratio is simply the ratio of a patient’s prothrombin time to an average population’s prothrombin time. A value near “1” would indicate that the patient has a typical blood clotting reaction. A higher value indicates that your blood is clotting slower than is typical, while a lower value (significantly below 1) means that your blood clots quicker than average.

Activated partial thromboplastin time (aPTT)

Activated partial thromboplastin time measures how quickly a patient’s blood clots when exposed to internal vascular damage. Similar to PT, this value is also measured in seconds, but it differs from PT by what is used to induce the clotting. In this way, it measures different coagulation factors than prothrombin time.

By looking at both PT and aPTT, a doctor can get a more complete picture of a person’s overall blood clotting process.