Once you have a decreased capacity for detoxification you may be more susceptible to pre-eclampsia

Dr Eric Steegers, University Hospital Nijmegen

The condition is a problem in around one in 20 pregnancies, and affects one in ten first time mothers.

Pre-eclampsia causes a pregnant woman's blood pressure to rise to very high levels.

This causes complications such as fluid retention and can lead to the condition eclampsia, which is associated with dangerous convulsions.

Researchers from the University Hospital Nijmegen, The Netherlands, looked for genetic defects in the blood samples of 183 women who were not pregnant, but who had a history of pre-eclampsia, and 151 healthy women.

The researchers focused on the gene responsible for the production of the enzyme epoxide hydrolase, which has a vital role in breaking down toxic compounds taken in, or produced by, the body.

They looked for defects in two sections of the gene - exon 3 and exon 4.

An exon 3 defect exaggerates the levels of epoxide hydrolase in the body.

Defect

One in three women with a history of pre-eclampsia carried the exon 3 defect.

Among healthy women the rate was only one in six.

There were no differences in the prevalence of exon 4 between the two groups.

Ninety six of the women with a history of pre-eclampsia had developed a syndrome known as HELLP - abnormally high liver enzymes and blood cell irregularities - which is frequently associated with pre-eclampsia.

But there was no difference in the genetic profiles of those who had and did not have the syndrome.

The researchers. lead by Dr Eric Steegers and Dr Wilbert Peters, say that in most cases epoxide hydrolase prevents reactive substances in the body from damaging cells.

But studies have shown that the enzyme can also activate other harmful compounds.

They conclude that an imbalance between toxic compounds and substances that neutralise and clear these toxins may be important in the development of pre-eclampsia.

Dr Steegers told BBC News Online: "This enzyme plays an important role in the detoxification system of the body.

"Detoxification is essential in combating pre-eclampsia.

"Once you have a decreased capacity for detoxification you may be more susceptible to pre-eclampsia."

Dr Steegers said the discovery could lead to new screening tests to identify women more at risk of the condition.

He said drugs, such as N-acetylcysteine, were also available to boost the body's capacity to rid itself of toxins.

Pre-eclampsia has also been linked to low levels of a hormone, angiotensin, which prevents high blood pressure, and to raised levels of a protein secreted by the placenta called neurokinin B (NKB).

The research is published in the Journal of Medical Genetics.