BLOOD-THINNING drugs such as aspirin could hold the key to treating a faulty gene that triggers miscarriages. One in four pregnancies ends in a woman miscarrying and British doctors now believe the problem may owe more to a genetic defect than to fertility complications.

Doctors at Care Fertility, a private provider of IVF treatment, have discovered that the gene can cause miscarriage in the mother even when it is present in the father. The fault causes improper blood clotting and can be treated with blood thinners such as aspirin and heparin...