Homozygosity for the C46T polymorphism of the F12 gene is a risk factor for venous thrombosis during the first pregnancy.
BACKGROUND
A first thromboembolic event during pregnancy and puerperium is predisposed to by polymorphisms G1691A in the factor V gene (F5) (F5G1691A) and G20210A in the prothrombin gene (F2) (F2G20210A).


OBJECTIVE
To study another potentially frequent thrombogenic polymorphism, C46T in the factor XII gene (F12) (F12C46T).


METHODS
The 32 463 previously asymptomatic women included in the NOHA First cohort in their first pregnancy were investigated for these three polymorphisms. No other constitutional or acquired thrombophilic risk factor was studied.


RESULTS
The overall incidence--absolute risk--of venous thromboembolic events (VTE) was 127 per 100,000 woman-years and was reduced to 22 per 100,000 women-years in women negative for the three polymorphisms (P < 0.0001). Homozygosity for F12C46T was associated with a significant relative risk (RR) of VTE [RR: 5.99, 95% confidence interval (95% CI): 2.1-17.3, P = 0.001], as was heterozygosity for F5G1691A (RR: 18.7, 95% CI: 8.3-42, P < 0.0001), heterozygosity for F2G20210A (RR: 14.3, 95% CI: 6.2-33.2, P < 0.0001), maternal age (RR: 1.18, 95% CI: 1.07-1.29, P = 0.0006), maternal body mass index (RR: 1.31, 95% CI: 1.11-1.55, P = 0.002), conceptus weight (percentiles adjusted for term of delivery; RR: 0.90, 95% CI: 0.88-0.93, P < 0.0001) and pre-eclampsia (RR: 3.03, 95% CI: 1.06-8.69, P = 0.039).


CONCLUSIONS
Homozygosity for the C46T polymorphism of the F12 gene is associated with venous thrombosis during the first pregnancy/puerperium in previously asymptomatic women.
Cochery-Nouvellon
E
E
Haematology Laboratory, University Hospital, Nimes, France.
Mercier
E
E
Lissalde-Lavigne
G
G
Daurès
J-P
JP
Quéré
I
I
Dauzat
M
M
Marès
P
P
Gris
J-C
JC
D000328:Adult; D015992:Body Mass Index; D015331:Cohort Studies; D005165:Factor V / Q000235:genetics*; D005174:Factor XII / Q000235:genetics*; D005260:Female; D020022:Genetic Predisposition to Disease; D006720:Homozygote; D006801:Humans; D011110:Polymorphism, Genetic; D011247:Pregnancy; D011249:Pregnancy Complications, Cardiovascular; D012307:Risk Factors; D020246:Venous Thrombosis / Q000150:complications / Q000175:diagnosis* / Q000453:epidemiology
D005165:Factor V; D005174:Factor XII