1: Doubilet PM, Benson CB, Bourne T, Blaivas M; Society of Radiologists in Ultrasound Multispecialty Panel on Early First Trimester Diagnosis of Miscarriage and Exclusion of a Viable Intrauterine Pregnancy, Barnhart KT, Benacerraf BR, Brown DL, Filly RA, Fox JC, Goldstein SR, Kendall JL, Lyons EA, Porter MB, Pretorius DH, Timor-Tritsch IE Diagnostic criteria for nonviable pregnancy early in the first trimester. N Engl J Med. 2013 Oct 10;369(15):1443-51. doi: 10.1056/NEJMra1302417. Review. PubMed PMID: 24106937.
Over the past two to three decades, pelvic ultrasonography and measurement of the serum concentration of human chorionic gonadotropin (hCG) (Table 1) have become mainstays in the diagnosis and management
of early-pregnancy problems. These tests, which allow earlier detection of pregnancy and more accurate diagnosis of its complications than were previously possible, have revolutionized the management of intrauterine pregnancies and markedly reduced the morbidity and mortality associated with ectopic pregnancy.
Although these tests have indisputable benefits, their misuse and misinterpretation can lead to interventions that inadvertently damage pregnancies that might have had normal outcomes. There are well-documented instances of women with intrauterine pregnancies treated with intramuscular methotrexate for suspected ectopic pregnancy, leading to failure of the pregnancy (“miscarriage”) or the birth of a malformed baby.5 Furthermore, considerable evidence suggests that mistakes such as these are far from rare. Malpractice lawsuits related to this type of error constitute “a rapidly increasing source of medical liability actions,” and there are online support groups for women erroneously treated in this manner.
When a woman presents with symptoms of pain or bleeding in early pregnancy, the main diagnostic possibilities are a currently viable intrauterine pregnancy, a failed (or failing) intrauterine pregnancy, and ectopic pregnancy. Serum hCG measurement and pelvic ultrasonography are commonly performed to aid in the differential diagnosis. At that point, unless a life-threatening situation dictates immediate management, a key question is: “Is there a chance of a viable pregnancy?” (Table 1). This question is central to management decision making in two main clinical contexts: intrauterine pregnancy of uncertain viability and pregnancy of unknown location. For a woman with an intrauterine pregnancy of uncertain viability, the answer to this question is central in deciding whether to evacuate the uterus. For a woman with a pregnancy of unknown location, the answer plays an important role in deciding whether to initiate treatment for a suspected ectopic pregnancy.
A pregnancy is diagnosed as nonviable if it meets one of the commonly accepted positivity criteria for that diagnosis, such as the embryonic size at which nonvisualization of a heartbeat on ultrasonography is diagnostic of failed pregnancy. The positivity criterion for any diagnostic test should depend, in part, on the downstream consequences of false positive and false negative diagnoses. In diagnosing nonviability of an early pregnancy, a false positive diagnosis — erroneously diagnosing nonviability — carries much worse consequences than a false negative diagnosis — failing to diagnose a pregnancy as nonviable. For either an intrauterine pregnancy of uncertain viability or a pregnancy of unknown location, the consequence of a false positive diagnosis of nonviability may be dire: medical or surgical intervention that eliminates or severely damages a viable pregnancy. This is much worse than the consequence of a false negative diagnosis in women with an intrauterine pregnancy of uncertain viability: a delay (usually by a few days) in intervention for a failed pregnancy. Likewise, for a pregnancy of unknown location, harming a potentially normal intrauterine pregnancy is considerably worse than the possible consequence of a false negative diagnosis: a short delay in treatment of an ectopic pregnancy in a woman who is being followed medically and has no ultrasonographically identifiable adnexal mass.
A false positive diagnosis of nonviable pregnancy early in the first trimester — incorrectly diagnosing pregnancy failure in a woman with an intrauterine gestational sac or ruling out viable intrauterine gestation in a woman with a pregnancy of unknown location — can prompt interventions that damage a pregnancy that might have had a normal outcome. Recent research has shown the need to adopt more stringent criteria for the diagnosis of nonviability in order to minimize or avoid false positive test results. The guidelines presented here, if promulgated widely to practitioners in the varivarious specialties involved in the diagnosis and management of problems in early pregnancy, would improve patient care and reduce the risk of inadvertent harm to potentially normal pregnancies.
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