Factor V Leiden as risk factor for unexplained stillbirth--a population-based nested case-control study.
BACKGROUND
Stillbirth is a relatively uncommon pregnancy complication in developed countries yet causing strong emotional burden. Thrombophilia has been associated with stillbirth but population-based studies are few. We assessed selected genetic and acquired parameters for the risk of unexplained stillbirth, including FV Leiden.


METHODS
We performed a population-based nested case-control study of 100,000 consecutive pregnancies in Finland. Cases and controls were identified by combining national registers and accepted according to strict criteria after checking their medical records. Stillbirth was defined as intrauterine fetal death > or =22weeks of gestation. We excluded stillbirths due to lethal congenital developmental conditions, umbilical cord complications, and infections. We studied 44 cases of unexplained stillbirth and 766 controls.


RESULTS
FV Leiden was associated with 3.8-fold (95% CI 1.2-11.6) risk for unexplained stillbirth, 3.9-fold (95% CI 1.1-13.9) risk for unexplained late stillbirth (> or =28weeks of gestation), and 10.8-fold (95% CI 2.1-55.3) risk for unexplained stillbirth with placental lesions. The same figures for singleton pregnancies were 3.1-fold (95% CI 0.9-10.9), 4.3-fold (95% CI 1.2-15.3), and 10.6-fold (95% CI 2.1-54.3). Slightly increased risk associated with blood group O was not statistically significant. We found a trend for increased risk in advanced maternal age and smoking during pregnancy. High pre-pregnancy BMI was not associated with increased risk, nor was low educational level or first pregnancy.


CONCLUSIONS
Our population-based study from a country with comprehensive prenatal care confirms the association between FV Leiden and unexplained stillbirth.
Hiltunen
Leena M
LM
Department of Hemostasis, Finnish Red Cross Blood Service, Helsinki, Finland. leena.hiltunen@bts.redcross.fi
Laivuori
Hannele
H
Rautanen
Anna
A
Kaaja
Risto
R
Kere
Juha
J
Krusius
Tom
T
Paunio
Mikko
M
Rasi
Vesa
V
D000293:Adolescent; D000328:Adult; D000367:Age Factors; D001789:Blood Group Antigens; D015992:Body Mass Index; D016022:Case-Control Studies; D003625:Data Collection; D005165:Factor V; D005260:Female; D005387:Finland / Q000453:epidemiology; D006801:Humans; D008875:Middle Aged; D011247:Pregnancy; D012307:Risk Factors; D012907:Smoking; D050497:Stillbirth / Q000453:epidemiology / Q000235:genetics*; D055815:Young Adult
D001789:Blood Group Antigens; C095381:factor V Leiden; D005165:Factor V