Only 50% of all conceptions result in a live birth (Figure 1). Human reproduction can therefore be viewed as being remarkably inefficient. However, the diametrically opposite opinion that it is in fact a very efficient and selective process, designed to optimize the outcome of pregnancy, deserves to be stated.

Between 65% and 90% of clinically recognized miscarriages are due to chromosome abnormalities, the occurrence of which is more closely related to basal follicle-stimulating hormone (FSH) levels rather than to maternal age alone. In contrast to women suffering a sporadic miscarriage, women who recurrently miscarry often, but not exclusively, lose pregnancies with a normal chromosome content. Using a combination of conventional Geimsa banding and the recently introduced technique of comparative genomic hybridization it has been reported that 54% of pregnancy losses amongst women with recurrent miscarriage are euploid. The challenge we face is to identify the causes of pregnancy loss amongst those couples who recurrently lose such euploid conceptions.

Whilst many conventionally held beliefs as to the aetiology and treatment of women with recurrent miscarriage have not withstood critical scrutiny, significant progress has been made. This progress is the subject of this review, which will also highlight potential areas of future research.