Diagnostic ultrasound ( PDFDrive )

1064 PART IV Obstetric and Fetal Sonography
A
B
FIG. 30.18 Ultrasound Findings Diagnostic of Early Pregnancy Failure. (A) TVS shows an embryo (calipers) measuring larger than 7 mm
without cardiac activity. (B) M-Mode conirms no fetal cardiac activity. See also Video 30.2.
Worrisome Findings of Early
Pregnancy Failure
Additional sonographic features may suggest an abnormal
outcome but lack the speciicity in isolation to diagnose early
pregnancy failure. hese include indings involving the gestational
sac, yolk sac, amnion, yolk sac, and embryo (Table 30.2).
FIG. 30.19 M-Mode Documenting Transmitted Maternal Uterine
Arterial Pulsations Mistaken for Fetal Cardiac Pulsations. Maternal
uterine pulsations (small arrow) are transmitted to the inferior portion
of the yolk sac (large arrow) and embryo (arrowhead) and mistakenly
measured as a slow embryonic cardiac activity at 75 beats/min. Key to
transmitted pulsation is noting the same rate throughout the different
depths of tissue insonated.
Furthermore, these parameters only apply to high-resolution
TVS and cannot be used for examinations performed with a
5-MHz TVS probe. Rowling et al. 73 studied early pregnancies
with lower-frequency TVS probes (5 MHz) as well as higherfrequency
probes (9-5 MHz broadband). he gestational sac was
irst seen at 6.4 mm in size with the lower frequency but at
4.6 mm with higher frequencies. A yolk sac was always seen in
normal pregnancies with a gestational sac greater than 5 mm,
and an embryo was always seen with a sac of 13 mm, using
frequencies above 5 MHz.
Embryos With Crown-Rump Length Less Than
7 mm and No Heartbeat
If on initial imaging, an embryo is seen measuring less than
7 mm and lacking cardiac activity, the indings are worrisome
but not entirely diagnostic of early pregnancy failure. As previously
stated, indings on ultrasound follow a typical pattern with an
embryo with a heartbeat demonstrable at 6 weeks. 40 Small embryos
usually demonstrate measurable cardiac activity, but lack of a
heartbeat in a small embryo of less than 7 mm may still result
in a normal pregnancy. Follow-up sonography should be performed
in these cases. Given the reliable pattern of growth, early
pregnancy failure can also be veriied on ultrasound by lack of
visualization of an embryo with cardiac activity on follow-up
scans. Embryonic cardiac activity should be documented by 11
days ater a scan demonstrating a gestational sac with a yolk sac
or by 14 days ater a scan demonstrating a gestational sac without
a yolk sac. If the pregnancy does not meet these milestones in
this time interval, early pregnancy failure can be reliably
diagnosed. 5
Gestational Sac With Mean Sac Diameter 16 to
24 mm and No Embryo
As mentioned earlier, using TVS indings of either an MSD
of 8 mm or more without a demonstrable yolk sac, or 16 mm
with no demonstrable embryo, is not typical and is suggestive of
pregnancy failure. Normal gestational sac growth is 1.1 mm/day.
Nyberg et al. 56 found that patients with early pregnancy failure had
MSD growth rates of less than 0.7 mm/day. his growth rate is