The study protocol, risks, benefits, visit schedule and consent will be reviewed with each potential subject. The informed consent will include the statement “if the treatment does not work, I have been advised to agree to a surgical abortion”. A haemoglobin and Rh factor will be obtained and reviewed. A focussed history and physical examination will be performed. Gestational dating will be done by endovaginal ultrasound using the following criteria: gestational age (days) = mean sac diameter (mm) + 30 or embryonic pole (mm) + 42. Mean sac diameter is used only if there is no embryonic pole. This method has been described by Rossavik and Goldstein.