Pregnancies of unknown location: diagnostic dilemmas and management

This review discusses various aspects of the management of women with pregnancies of unknown location.

The prevalence of pregnancies of unknown location is dependent on the quality of scanning for a given early-pregnancy unit. The higher the quality of scanning, the better the detection of ectopic pregnancy using ultrasound as a single diagnostic test, which in turn results in fewer women being classified with a pregnancy of unknown location. Varying the discriminatory zone does not significantly improve the detection of ectopic pregnancies in a pregnancy of unknown location population. A single serum human chorionic gonadotrophin, when used in a specialized transvaginal scanning unit, is not only potentially falsely reassuring but also unhelpful in excluding the presence of an ectopic pregnancy. A single-visit approach has also been shown to be ineffective. The vast majority of women with a pregnancy of unknown location are at low-risk for ectopic pregnancy. Traditional strategies are capable of detecting the failing pregnancies of unknown location and intra-uterine pregnancies within a pregnancy of unknown location population, but they lack sensitivity for detecting ectopic pregnancies. This justifies the recent development and use of mathematical modelling techniques to predict ectopic pregnancies in the pregnancies of unknown location population.

New mathematical models have been developed to predict the outcome of pregnancies of unknown location; however, prospective studies are needed to assess the reproducibility of these models in different centres on different populations. Hopefully such models will enable the clinician to correctly classify pregnancies of unknown location earlier, in turn reducing the number of follow-up visits.