The outcomes of interest are an intrauterine pregnancy (which may be viable or non-viable) or an ectopic pregnancy. A viable intrauterine pregnancy is defined as ultrasonographic identification of an intrauterine gestation sac with a fetal pole of any length with demonstrable fetal heart pulsations. A non-viable intrauterine pregnancy is defined as either an empty intrauterine gestation sac with mean sac diameter greater than 25mm or an intrauterine gestation sac containing a fetal pole with crown rump length greater than 7mm with no demonstrable fetal heart pulsations or in the absence of a viable embryo, no significant increase in the growth of the gestation sac or length of the fetal pole on two ultrasound scans performed more than 7 days apart. Where women undergo surgical or medical management of miscarriage, histological confirmation of the products of conception will be obtained when possible. Ectopic pregnancies will be confirmed either by direct visualisation during surgery with histological confirmation, or, in those managed medically with methotrexate or conservatively, unequivocal identification of an ectopic pregnancy on ultrasound scan. Ultrasonographic appearances indicative of an ectopic pregnancy will include: an empty endometrial cavity with either an inhomogenous adnexal mass or an empty extra-uterine sac or a yolk sac or fetal pole with or without cardiac activity in an extra-uterine sac. Following the reference standard, any pregnancy which does not fall into one of these categories will be excluded from the study. These included resolving or persisting pregnancies of unknown location.