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The gestational sac is the first structure seen in pregnancy by ultrasound as early as 4.5 to 5 weeks of gestational age, but it is only 97.6% specific for the diagnosis of intrauterine pregnancy. Early pregnancy obstetric ultrasound is essential in differentiating between intrauterine pregnancy, pregnancy of unknown location, and ectopic pregnancy as well as assessing pregnancy viability. This activity reviews the interpretation of early pregnancy obstetric ultrasound findings and highlights the role of the interprofessional team in evaluating and providing follow up care for patients diagnosed with a pregnancy of unknown location or uncertain viability. Objectives: Describe embryonic development and sonographic features of early pregnancy between 5 and 8 weeks of gestation and their specificity for establishing the diagnosis of intrauterine pregnancy. Review the technique for performing a comprehensive first-trimester two-dimensional obstetric ultrasound. Summarize currently used criteria for establishing early pregnancy failure diagnosis. Explain the importance of collaboration and communication amongst the interprofessional team to improve outcomes for patients with a diagnosis of pregnancy of unknown location or uncertain viability. Access free multiple choice questions on this topic.

The gestational sac is a fluid-filled structure surrounding an embryo during the first few weeks of embryonic development.  It is the first structure seen in pregnancy by ultrasound as early as 4.5 to 5 weeks of gestational age and is 97.6% specific for the diagnosis of intrauterine pregnancy (IUP).[1]

Females presenting for evaluation of abdominal pain or vaginal bleeding with elevated B-hCG levels present a diagnostic dilemma in the early stage of pregnancy if an imaging study does not clearly demonstrate an intrauterine pregnancy.  An interprofessional team effort will improve outcomes in diagnosing and treating these cases. In a female of childbearing age pregnancy test is the first step in the evaluation of their presenting complaint. If the patient is clinically stable, and a pregnancy test is positive, a pelvic ultrasound is necessary to evaluate the location of the pregnancy.  If there is an ectopic pregnancy identified, the OBGYN team must be involved in the patient’s care as soon as possible. However, in cases of pregnancy of unknown location, close follow up must be arranged by the evaluating clinician, and strict return precautions are necessary for the patient, given the possibility of early ectopic pregnancy.  A nurse with obstetric/neonatal specialization may be of great assistance, as they can help irrespective of the diagnosis and direction of treatment by providing counsel to the patient and assisting in any procedures. This situation requires diligence and communication between different providers to ensure proper follow-up. Radiologists must be familiar with normal and abnormal ultrasound findings of early pregnancy and use the most conservative criteria when assessing the viability and diagnosing pregnancy failure. The referring physician should provide clinical history and order B-hCG quantitative level to assist the radiologist in the interpretation of imaging studies. As a team, referring physicians, nurse practitioners, OBGYN specialists, and radiologists must collaborate to protect the mother and baby and to intervene only in cases of definitive ectopic or failed pregnancy. (Level I) The interprofessional team approach is necessary to manage these cases and arrive at the best management option. [Level 5]