LONDON (Reuters) - British fertility researchers have developed an accurate way to predict which pregnancies are most likely to miscarry and say it could help doctors target treatment at women who really need it. In a study presented at European Society for Human Reproduction and Embryology conference in Stockholm, researchers found six factors with the greatest impact on miscarriage risk a history of sub fertility, levels of progesterone and of the pregnancy hormone human chorionic gonadotrophin (hCG), foetus length, the extent of bleeding, and the babys gestational age. Individually, these factors were unable to predict accurately the risk of miscarriage, but when the researchers combined two of them bleeding and hCG levels to create a Pregnancy Viability Index (PVI), they found this was a consistently reliable predictor of miscarriage. In Britain, around 250,000 miscarriages occur every year, causing significant psychological distress to affected women and their families.