D-dimer concentrations in normal pregnancy: new diagnostic thresholds are needed

Area of Science:

• Obstetrics and Gynecology
• Hematology
• Diagnostic Medicine

Background:

• Pregnancy naturally increases D-dimer concentrations above typical thresholds.
• This elevation can lead to false-positive results for venous thromboembolism (VTE) in pregnant patients.
• Conventional D-dimer cutoffs may not be suitable for diagnosing VTE during gestation.

Purpose of the Study:

• To investigate the impact of normal pregnancy on D-dimer levels.
• To assess the trend of D-dimer concentration throughout pregnancy.
• To determine the utility of the standard D-dimer threshold in pregnant women.

Main Methods:

• Enrolled healthy women planning pregnancy with no pre-existing conditions affecting D-dimer.
• Collected blood samples for quantitative D-dimer and fibrinogen assays preconception, each trimester, and 4 weeks postpartum.
• Excluded participants with fetal loss or preeclampsia.

Main Results:

• D-dimer concentrations progressively increased with each trimester of pregnancy.
• Preconception, 79% of women had D-dimer <0.50 mg/L; this dropped to 22% in the second and 0% in the third trimester.
• No significant correlation was found between D-dimer and fibrinogen levels during pregnancy.

Conclusions:

• Normal pregnancy leads to a continuous rise in circulating D-dimer.
• The D-dimer test, using a 0.50 mg/L cutoff, is not useful for ruling out VTE in the third trimester.
• New trimester-specific D-dimer thresholds are required for accurate VTE diagnosis in pregnancy.