The index test will be performed by a single investigator with experience in early pregnancy ultrasound following standard operating procedures using a Voluson E8 machine with a high frequency (5-9MHz and 9-12MHz) transvaginal probe. During the early scan the presence or absence of the following structures will be recorded: an intrauterine fluid collection (defined as a uniformly round, hypoechoic structure with an echogenic rim); the double decidual sac sign (DDSS) (defined as two concentric echogenic rings of tissue that surround the intraendometrial fluid collection that impress upon the endometrial stripe); yolk sac (defined as a spherical, hyperechoic ring situated eccentrically within the gestation sac); and fetal pole (defined as a small linear echogenic structure adjacent to the yolk sac, on the side closest to the gestational sac). If more than one intrauterine fluid collection is visualized then each will be considered as a separate entity. The findings from the early scan will be interpreted immediately and recorded separate to the main clinical notes. Participants will be excluded further from the study if at this point no intrauterine fluid collection is detected or if an intrauterine fluid collection containing a yolk sac or fetal pole is identified. Referral pathways to local Early Pregnancy Assessment Units (EPAU) will be in place for any woman in whom this early scan is strongly suggestive of an ectopic pregnancy, for example if there was an empty endometrial cavity and 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.