Women who suffer repeated unexplained miscarriages can be helped to have babies by the use of genetic analysis, say experts.

Researchers say the problem could be addressed by simply analysing the genetic make-up of embryos before they are placed in the womb - a technique known as preimplantation genetic diagnosis (PGD).

Researcher Carmen Rubio told the European Society of Human Reproduction and Embryology annual conference in Vienna that her research suggested that chromosomal abnormalities were a key cause of the problem.

These abnormalities, also known as aneuploidies, can be detected with a simple genetic test.

Ms Rubio and her colleagues at the Instituto Valenciano de Infertilidad, Valencia, Spain, achieved "normal" pregnancy rates and a decreased risk of miscarriage in women with a history of recurrent miscarriage (RM) and "failed" implantation (FI).

The team screened the embryos for chromosomal abnormalities during IVF and transferred only genetically-normal embryos to the women's wombs.

Non-inherited abnormalities in the number of chromosomes are a common cause of miscarriage.

Embryos which fail to implant successfully during fertility techniques such as IVF and ICSI often have these abnormalities as well.

High pregnancy rates and a decreased risk of further miscarriages can be achieved

Carmen Rubio,Instituto Valenciano de Infertilidad, Valencia

The researchers examined the possibility that similar abnormalities were an important factor in women with RM or IF.

They carried out PGD in 71 RM couples where the woman had had two or more unexplained miscarriages, and in 42 FI couples who had had three or more unsuccessful IVF or ICSI attempts in the previous four years.

A control group of 28 fertile women who were undergoing PGD for sex-linked diseases was added to the study.

The sampling was achieved by taking a single cell from the embryo at a very early stage of development - this does not harm the embryo.

Higher figures

The researchers found that the percentage of embryos with abnormal chromosomes was approximately a third higher in the RM and IF groups, compared with the control group.

Ms Rubio said: "These differences were especially remarkable in embryos from women under 37 years old; these were twice as likely to be abnormal."

This is significant because women under 37 are a better group for comparing the incidence of chromosomal abnormalities in embryos in RM and IF patients. Once a woman is over 37 her age the risk of abnormalities increases.

After transferring only the normal embryos to the women, the researchers achieved similar pregnancy rates in all three groups. The miscarriage rate was similar too.

Ms Rubio said: "Our study shows that, in some couples suffering from repeated unexplained miscarriages or implantation failure, chromosomal abnormalities in the embryo can be the cause of the problem.

"High pregnancy rates and a decreased risk of further miscarriages can be achieved in these couples by using PGD to select only the normal embryos to be transferred into the uterus.

"PGD could also be used as a diagnostic tool to identify couples with an increased risk of producing embryos with chromosomal abnormalities and even couples whose embryos are all abnormal."