Diagnostic Ultrasound - Abdomen and Pelvis

Failed First Trimester Pregnancy
Diagnoses: Female Pelvis
TERMINOLOGY
• Failed first trimester pregnancy: Collection of specific
diagnoses of pregnancy failure
IMAGING
• Anembryonic pregnancy: Gestational sac (GS) with mean
sac diameter ≥ 25 mm and no embryo
• Embryonic demise: Embryo with CRL ≥ 7 mm with no
cardiac activity
• Spontaneous abortion: May be inevitable/impending,
incomplete, or complete
○ Inevitable: GS herniating into or located centrally in
cervical canal with open internal os
○ Incomplete: Heterogeneous endometrial thickening ±
color Doppler flow, ± open cervical os
○ Complete: Thin, undistorted endometrial stripe;
indistinguishable by US from ectopic or early
nonvisualized IUP
KEY FACTS
– Must correlate with hCG trend, clinical presentation of
bleeding, and possibly repeat US
TOP DIFFERENTIAL DIAGNOSES
• Normal early intrauterine pregnancy (IUP)
• Pseudosac of ectopic pregnancy (EP)
• Retained products of conception (RPOC)
• Gestational trophoblastic disease (GTD)
• Cervical ectopic pregnancy
CLINICAL ISSUES
• New guidelines for diagnosing failed pregnancy establish
more stringent criteria to minimize potential of harming
early IUP
• Single hCG measurement does not reliably distinguish
between viable IUP, nonviable IUP, and ectopic pregnancy
• Follow-up hCG and ultrasound are often most prudent
course when findings are not clear-cut
(Left) Longitudinal
transabdominal ultrasound
shows an angular, enlarged
gestational sac ſt with a
mean sac diameter (MSD) of
37 mm. There were no
recognizable internal
structures, which is
compatible with an
anembryonic pregnancy. Note
the poorly echogenic cystic
decidua st. (Right)
Longitudinal transvaginal
ultrasound shows an empty
gestational sac herniating into
the cervix through the open
internal os ſt. Note internal
echoes in the sac compatible
with hemorrhage.
(Left) Longitudinal
transvaginal ultrasound shows
a large intrauterine
gestational sac (GS) with
an embryo ſt. The sac is
irregular in shape with poor
decidual reaction. The amnion
is seen surrounding the
embryo st. (Right) M-mode
ultrasound in the same patient
shows the expanded amnion
sign compatible with
embryonic demise. The amnion
st is seen surrounding the
embryo, which measures >
7mm and shows no cardiac
activity.
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