First-trimester emergencies: a radiologist's perspective.

The purpose of this article is to help the practitioner ensure early diagnosis and response to emergencies in the first trimester by reviewing anatomy of the developing embryo, highlighting the sonographic appearance of common first-trimester emergencies, and discussing key management pathways for treating emergent cases. First-trimester fetal development is a stepwise process that can be challenging to evaluate in the emergency department (ED) setting. This is due, in part, to the complex anatomy of early pregnancy, subtlety of the sonographic findings, and the fact that fewer than half of patients with ectopic pregnancy present with the classic clinical findings of a positive pregnancy test, vaginal bleeding, pelvic pain, and tender adnexa. Ultrasound (US) has been the primary approach to diagnostic imaging of first-trimester emergencies, with magnetic resonance imaging (MRI) and computed tomography (CT) playing a supportive role in a small minority of cases. Familiarity with the sonographic findings diagnostic of and suspicious for early pregnancy failure, ectopic pregnancy, retained products of conception, gestational trophoblastic disease, failed intrauterine devices, and complications associated with assisted reproductive technology (ART) is critical for any emergency radiologist. Evaluation of first-trimester emergencies is challenging, and knowledge of key imaging findings and familiarity with management pathways are needed to ensure early diagnosis and response.