A longitudinal study of 21 pregnant women has been undertaken using a
variety of factor VII assays, including factor VIIa, to investigate th
e increase of factor VIIc. All assays demonstrated significant rises (
p <0.001), most marked for factor VIIa (82%) and factor VIIc rabbit (8
1%). Smaller rises were seen for factor VIIc bovine (50%) and VII anti
gen (40%). Three indirect measures of activity state, factor VIIc rabb
it:antigen, bovine:antigen and bovine:rabbit provided conflicting data
. Factor VIIa:antigen showed a significant increase of 36% (p <0.001).
Within individual pregnancies the change in factor VIIc rabbit and an
tigen correlated with maternal weight gain (p <0.05). Two activity sta
te measures, bovine:rabbit and bovine:antigen, showed negative correla
tion with birthweight. The increases in both zymogen and in activity s
tate appear to contribute to the factor VIIc rise. The extent of this
rise appears to be influenced by maternal weight gain. Increased facto
r VII activation is associated with reduced foetal growth.