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Tuesday, 29 January, 2002, 23:57 GMT
Rogue gene link to miscarriages
Pregnant woman
Some women suffer repeated miscarriages
Women who carry a rogue blood clot gene are at greater risk of miscarrying their baby, research suggests.

The defective gene, known as Factor V Leiden (FVL), was associated with a poor rate of live births among women with a history of recurrent miscarriages.

For women with a mutation of FVL, who had a history of recurrent miscarriage at about 12 weeks, less than 40% had live births.


Factor V Leiden is an important and potentially treatable cause of recurrent miscarriages

Dr Raj Rai, study co-author

This compared to almost 70% of those in a control group of women with a similar history, but with a normal copy of the gene.

Dr Raj Rai, from Imperial College London, which carried out the study, said: "The low live birth rate in our study suggests that Factor V Leiden is an important and potentially treatable cause of recurrent miscarriages.

"Our findings support a hypothesis that recurrent miscarriage is due in some cases to an exaggeration in the pro-thrombotic (clot promoting) changes that occur during normal pregnancy.

"There are also indications from other research we have done that a proportion of women with recurrent miscarriage are in a pro-thrombotic state even when they are not pregnant.

"Clearly, this may have implications for their future health beyond their reproductive years."

Thrombosis threat

Recurrent miscarriage is defined as losing three or more babies.

Researchers think other genetic factors as well as FVL probably increase women's risk of having a miscarriage.

All these genetic factors are thought to increase the risk of blood clots forming in the blood vessels of the placenta.

The team at Imperial College has now called for doctors to screen women for FVL mutations if they have a history of recurrent miscarriages associated with placental thrombosis.

It also wants targeted anti-blood clotting treatment for these women to be tested in a randomised clinical trial.

Routine tests

This is a move welcomed by the Miscarriage Association, whose director Ruth Bender Atik said: "I very much like what Dr Rai says and how he points out that it isn't a simple cause and effect situation, but needs to be looked at it in combination with other things.

"He is also saying this is one of the areas that should be investigated, but not in isolation.

"We would like to see tests carried out for FVL mutations in cases of recurrent miscarriage."

Dr Rai said there was no justification for screening women routinely prior to pregnancy, nor was it appropriate to undertake routine anti-clotting treatment outside of a clinical trial.

The study looked at 25 women with FVL and a history of recurrent miscarriage or at least one late miscarriage (later than 12 weeks into pregnancy) and compared them with a control group of 198 women with a similar history, but without the defective gene.

The live birth rate for the FVL group with early miscarriages was 37.5% (control group 69.3%) and for those with a late miscarriage it was 11.1% (controls 48.9%).

FVL is carried by 5% of Caucasians, but is rarely found among black people.

It carries a four-fold risk of venous thrombosis and a 10-fold risk if the carrier is taking the oral contraceptive pill.

The research is published in the journal Human Reproduction.

See also:

26 Jul 01 | Health
Miscarriage gene identified
13 Jan 00 | Health
Genetic miscarriage risk
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