Factor V (plasma)
Factor V is a liver-derived coagulation cofactor essential for thrombin generation. Unlike many clotting factors, Factor V tends to remain stable or slightly decrease in late pregnancy.
| Units | Nonpregnant Adult | 1st Trimester | 2nd Trimester | 3rd Trimester |
|---|---|---|---|---|
| % | 50 – 150 | 75 – 95 | 72 – 96 | 60 – 88 |
Pregnancy physiology
- Factor V levels generally remain stable or slightly decline in late gestation.
- Unlike Factors VII, VIII, and X, Factor V does not significantly rise in pregnancy.
- Levels reflect hepatic synthesis and consumption balance.
Causes of low Factor V
- Inherited Factor V deficiency
- Liver disease (impaired synthesis)
- Disseminated intravascular coagulation (DIC)
- Massive transfusion (dilutional)
- Severe systemic illness or sepsis
Interpret alongside fibrinogen, platelets, PT/aPTT, and clinical context (e.g., HELLP, abruption).
Causes of elevated Factor V
- Acute inflammatory states
- High-estrogen states (mild effect)
- Assay or laboratory variability
Factor V Leiden does not elevate the Factor V level—it alters function and requires APC resistance testing or genotyping.
Clinical interpretation & pregnancy considerations
- Low Factor V contributes to bleeding risk when combined with thrombocytopenia or hypofibrinogenemia.
- Consider DIC in the setting of severe preeclampsia/HELLP, abruption, or postpartum hemorrhage.
- Inherited Factor V deficiency requires multidisciplinary delivery planning.
- Factor V Leiden mutation usually shows normal activity levels.
References
- Abbassi-Ghanavati M, Greer LG, Cunningham FG. Pregnancy and laboratory studies: a reference table for clinicians. Obstet Gynecol. 2009;114:1326–31.