Ultrasound, and in particular transvaginal sonography (TVS), plays an important role in the management of women with acute gynaecology conditions. This study compared the cost-effectiveness of two models of out-of-hours care for women in an acute gynaecology setting. In the ultrasound-based model, the on-call registrar with ultrasound experience managed such patients after performing pelvic ultrasound as a part of the initial assessment. On the other hand, in the traditional model of care the on-call registrar managed the patients without the use of ultrasound. The conclusion is that the use of ultrasound by the on-call registrars has significant cost implications through reduced hospital admissions. It leads to improved outcomes of such patients through timely diagnosis and treatment.