Factor V Leiden mutation in relation to fecundity and miscarriage in women with venous thrombosis.
BACKGROUND
Factor V Leiden mutation (Arg506Gln) increases the likelihood of venous thrombosis; it may also have a positive effect through facilitation of embryo implantation. This may manifest itself as a reduced time to pregnancy (increased fecundity) and fewer miscarriages in the first trimester.


METHODS
From March 1999 onwards, consecutive patients with a first venous thrombosis (VT) were recruited. The first 115 female VT patients with factor V Leiden and 230 age-matched female VT patients without factor V Leiden were included. All patients, unaware of their genotype, received a structured questionnaire.


RESULTS
Of the 297 (86%) women who returned the questionnaire, 220 had been pregnant at least once. Time to first pregnancy was unaffected by carrier status: 58% factor V Leiden carriers reported a pregnancy within 3 months compared to 54% non-carriers. The miscarriage proportion was 14%, similar in both groups. First trimester miscarriage was less frequent among carriers (46%) than among non-carriers (95%) (relative risk 0.5, 95% confidence interval 0.3-0.9).


CONCLUSIONS
Factor V Leiden mutation may support embryo implantation, as factor V Leiden carriers had fewer miscarriages in the first trimester with a similar overall miscarriage rate. Miscarriage of embryos with poor viability may be postponed until the second trimester in factor V Leiden carriers. Fecundity was not influenced by factor V Leiden status.
van Dunné
F M
FM
Department of Obstetrics, Gynaecology and Reproductive Medicine, Leiden University Medical Center, P.O.Box 9600, 2300 RC Leiden, The Netherlands.
Doggen
C J M
CJ
Heemskerk
M
M
Rosendaal
F R
FR
Helmerhorst
F M
FM
D000022:Abortion, Spontaneous / Q000150:complications / Q000453:epidemiology*; D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D005165:Factor V / Q000235:genetics*; D005260:Female; D005298:Fertility; D006579:Heterozygote; D006801:Humans; D015994:Incidence; D008875:Middle Aged; D009154:Mutation; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D011795:Surveys and Questionnaires; D020246:Venous Thrombosis / Q000150:complications / Q000235:genetics* / Q000503:physiopathology*
C095381:factor V Leiden; D005165:Factor V