More than half of recurrent miscarriages are caused by a random chromosomal abnormality in the fetus that was not inherited from the parents, according to a study conducted at Tel Aviv’s Sourasky Medical Center.The research, led by Prof. Yuval Yaron, head of Ichilov Hospital’s prenatal diagnosis unit, has just been published in the Journal of Maternal Fetal & Neonatal Medicine.“Identification of the chromosomal disorder can eliminate the need for complex and costly inquiries or drug treatments, such as anticoagulants, which are also available without diagnosis,” he said.The study, which has been conducted at the hospital’s genetic institute for more than a decade, found that the most common cause of repeated miscarriages was a chromosomal disorder in the fetus, which was identified in 144 samples of the aborted fetal material, and that random chromosomal abnormalities were observed in 54% of the cases.There was a statistical difference between the percentage of chromosomal disorders and the number of miscarriages experienced by the woman. After two miscarriages, the odds of chromosomal abnormalities in the fetus were 57.4%. After five or more miscarriages, the risk of chromosomal abnormalities in the fetus was 59.1%.The causes of the problem were an extra X chromosome (18%), an extra chromosome #16 (15%), an extra chromosome #15 (13%) or an extra chromosome #21, which has been associated with Down syndrome (10%), but only a small proportion of the cases were due to an inherited chromosomal disorder. Spontaneous abortion is one of the most common complications of pregnancy – affecting some 15% of pregnancies. About a quarter of all women will experience at least one miscarriage during their lifetime, but about 1% to 2% of women will experience repeated miscarriages, defined as three miscarriages or more.There are many reasons for repeated miscarriages, including coagulation disorders, uterine malformations, hormonal disorders and the like. But identifying a major cause of repeated miscarriages makes it possible to reduce the risk of another miscarriage and offer treatments to increase the likelihood of a successful pregnancy.Screening measures for couples with repeated miscarriages have included blood tests to identify coagulation disorders or hormonal abnormalities, chromosome examination of the parents (karyotype) and a hysteroscopy for the detection of uterine defects. These tests are complex, costly and delay further pregnancies.It is usually unnecessary to undergo complex and costly investigations and drug treatments such as anticoagulants, Yaron said. If there is a hereditary chromosomal disorder, abortion can be prevented by pre-implantation genetic diagnosis of embryos and choosing only healthy fetuses conceived by in-vitro fertilization. “In the case of a randomized chromosomal disorder, there is no need to expand the investigation, and the couple can try to conceive again without additional investigation or treatment,” he said.