More conservative diagnostic thresholds, published Oct. 10 in the New England Journal of Medicine (NEJM), will help reduce the risk that a possibly normal first trimester pregnancy is misdiagnosed as nonviable, say experts from radiology, obstetrics-gynecology and emergency medicine.
The 15-member expert panel that reviewed and updated the current first trimester ultrasonography criteria for determining a nonviable pregnancy was convened by the Society of Radiologists in Ultrasound (SRU). Changes in the criteria include:
Raising embryo size standard for a nonviable pregnancy from at least 5 millimeters without a heartbeat to at least seven millimeters without a heartbeat.
Raising the standard for nonviability based on the size of a gestational sac without an embryo from 16 to 25 millimeters.
The panel also noted that the commonly used "discriminatory level" of the pregnancy blood test is unreliable for excluding a viable pregnancy and physicians should not take any action that could damage an intrauterine pregnancy based on a single blood test, if the ultrasound findings are inconclusive and the woman is in stable condition.
“We urge providers to familiarize themselves with these recommendations and factor them into their clinical decision-making,” said Peter M. Doubilet, MD, PhD, of Brigham and Women's Hospital and Harvard Medical School in Boston, the report's lead author in the press release. Read standards in the NEJM here.
With a few exceptions such as possible ectopic pregnancies in ER patients that would likely be lost to follow up once they leave the ER, there is no rush to diagnose a nonviable pregnancy noted the experts. Therefore, setting more conservative criteria makes sense.
"With improvement in ultrasound technology, we are able to detect and visualize pregnancies at a very early age,” noted Kurt T. Barnhart, MD, MSCE, an obstetrician-gynecologist at the Perelman School of Medicine at the University of Pennsylvania and a member of the SRU Multispecialty Panel, in the press release. These guidelines represent a consensus that will balance the use of ultrasound and the time needed to ensure that an early pregnancy is not falsely diagnosed as nonviable. There should be no rush to diagnose a miscarriage; more time and more information will improve accuracy and hopefully eliminate misdiagnosis."