Diagnostic ultrasound ( PDFDrive )

1068 PART IV Obstetric and Fetal Sonography
an echogenic yolk sac, with all 19 chromosomally abnormal,
and the other 20 (51%) had an echogenic yolk sac as the only
unusual inding, with all delivered normally.
FIG. 30.25 Embryonic Bradycardia. A small embryo in a 10-week
by dates pregnancy with a heart rate of 69 beats/min. This embryo later
was found to not have cardiac activity. A round amniotic sac is seen on
the left and the large yolk sac is seen to the right of the embryo.
Embryonic Bradycardia
Although embryonic cardiac activity indicates that the embryo
is alive at examination, an abnormally slow heart rate may predict
impending demise. he embryonic heart rate increases between
6 and 9 weeks’ gestation. At 6 weeks’ menstrual age, the mean
embryonic heart rate ranges from 90 to 133 bpm, and at 9 weeks’
gestation it ranges from 144 to 170 bpm. he lower the heart
rate is, the greater the chance is of miscarriage. Doubilet and
Benson 49 found that a heart rate less than 80 bpm in embryos
with a CRL less than 5 mm was universally associated with
subsequent embryonic demise. A rate of 80 to 90, 90 to 99, and
100 bpm were associated with risk of demise of 64%, 32%, and
11%, respectively. Rates below 100 bpm before 6.3 weeks’ gestation
and below 120 bpm between 6.3 and 7 weeks’ gestation are
associated with a high risk of miscarriage. 49,83 Additionally, even
A
B
ys
a
C
e
FIG. 30.26 Embryonic Demise With Yolk Sac Calciication.
(A) TVS color Doppler at 7 weeks menstrual age (CRL,
6.5 mm) shows an embryo without cardiac activity (no color) and
a normal-appearing yolk sac (arrow). (B) Repeat scan 5 days later
shows no change in the size of the embryo (calipers) and a dense
yolk sac (arrow) with faint distal shadowing. (C) In a different
pregnancy, TVS sagittal scan shows calciied yolk sac (ys). No
cardiac activity was identiied in embryo with CRL of 18 mm. a,
Amnion; e, embryo. See also Video 30.4.