Early pregnancy failure
The term “early pregnancy loss” or EPF refers to a nonviable, intrauterine pregnancy with either a gestational sac that is empty or contains an embryo or fetus without heart activity within the first 12 6/7 weeks of gestation. EPF occurs in 15% of all clinically recognized pregnancies and most frequently results from a spontaneous chromosomal abnormality of the embryo. Depending on clinical presentation and U/S findings EPF can be divided into several categories.
- Anembryonic pregnancy, also known as a blighted ovum: this EPF is characterized by no embryo development once a gestational sac reaches 25 mm (Figure 3A).
- Embryonic/fetal death is also known as missed abortion. This is characterized by an IUP with an embryo that either never developed a heartbeat or that previously had a heartbeat, but now lacks one (Figure 3B).
- Spontaneous abortion is characterized by a previously seen IUP, followed by cramping and bleeding. A spontaneous abortion may either be complete, as the uterus expels the products of conception (POCs) on its own, or inevitable, with an open os and gestational sac in the lower uterine segment.
Previous recommendations did not have a 0% false positive rate, and therefore a number of viable pregnancies were destined to be treated as though they were losses. Traditional data on EPF utilized a crown–rump length of 5 mm without cardiac activity, or an empty gestational sac of 16 mm as diagnostic criteria.11,12 Recent prospective studies, however, revealed an 8.3% false-positive rate with this crown–rump length and a 4.4% false-positive rate with this gestational sac diameter. In thoser studies, it was necessary to achieve a 0% false-positive rate, a crown–rump length of 5.3 mm without cardiac activity, or an empty gestational sac of 21 mm. The same group also found that an empty gestational sac 7 days from initial identification of the sac was 100% diagnostic of EPF.1,3,4 In response, the American College of Obstetricians and Gynecologists (ACOG) released in May 2015 an updated Practice Bulletin with diagnostic criteria of EPF incorporating guidelines from the Society of Radiologists in Ultrasound (SRU). The new guidelines allow for diagnosis of EPF in the situations summarized in Table 2 (from AGOG Bulletin #150, May 2015). The new criteria for EPF are less strict, allowing for lengthening of the waiting time prior to EPF diagnosis and thus minimizing the false-positive rate. If the diagnosis is at all in doubt, serial U/S assessment is recommended.
None of the authors report a conflict of interest to report with respect to the content of this article.
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