Diagnostic ultrasound ( PDFDrive )

CHAPTER
43
Sonographic Evaluation of
the Placenta
Thomas D. Shipp
SUMMARY OF KEY POINTS
• The placenta undergoes tremendous development within
the irst half of pregnancy yet continues to mature and
develop during the gestation.
• A placenta that lies near or over the internal cervical os is
common early in gestation, yet most of these will resolve
by the end of pregnancy. Ultrasound, especially
transvaginal sonography, is instrumental to determine
placental position.
• Placenta accreta is increasingly common and ultrasound is
vital for its identiication, especially in patients at high risk
for its development. Sonographic indings most important
for identifying placenta accreta are placental lacunae, loss
of the placental-myometrial hypoechoic space,
abnormalities of the uterine-bladder interface, and color
Doppler abnormalities.
• Placental infarctions are commonly identiied within the
placenta, especially in patients at high risk for their
development (e.g., those who have preeclampsia, maternal
vascular disease, or thrombophilia).
• Abnormalities of placental shape are common, as are
differences in location of the placental umbilical cord
insertion.
• The presence of a vasa previa is associated with increased
perinatal morbidity and mortality rates. Vasa previa should
be evaluated for all gravidas, especially for those with an
increased risk of its development.
• Those parturients with abnormal postpartum bleeding
should be evaluated for the presence of retained products
of conception. Echogenic endometrial masses in these
patients strongly suggest the presence of retained
products of conception.
CHAPTER OUTLINE
PLACENTAL DEVELOPMENT
Placental Appearance
Placental Size
Placental Vascularity and Doppler
Ultrasound
Amnion-Chorion Separation
Elastography
PLACENTA PREVIA
PLACENTA ACCRETA
PLACENTAL ABRUPTION
PLACENTAL INFARCTION
PLACENTAL MASSES
MESENCHYMAL DYSPLASIA OF THE
PLACENTA
MOLAR GESTATIONS
MORPHOLOGIC PLACENTAL
ABNORMALITIES
Circumvallate Placenta
Succenturiate Lobe
Bilobed Placenta
UMBILICAL CORD
Size and Appearance
Insertion Into the Placenta
Velamentous and Marginal Cord
Insertions
Vasa Previa
PLACENTA DURING LABOR AND
POSTPARTUM
Third Stage of Labor
Retained Products of Conception
CONCLUSION
The use of ultrasound to evaluate the placenta is routine among
the majority of pregnant American women because they
have at least one ultrasound examination during pregnancy. A
wide range of pregnancy complications result from abnormal
placental development, including preeclampsia, intrauterine
growth restriction (IUGR), and abruption. Other placental and
umbilical cord abnormalities, such as placenta previa, placenta
accreta/increta/percreta, or vasa previa, may cause major maternal
and fetal complications, especially if not recognized antenatally.
Timely recognition of these abnormalities can lead to improved
management of pregnancy and delivery. hus careful examination
of the placenta by ultrasound can contribute directly to enhanced
patient care and improved outcomes.
PLACENTAL DEVELOPMENT
he early developing embryo is surrounded by amnion and
chorion. Villi cover the entire surface of the chorion up to about
8 weeks of gestation (Fig. 43.1). he villi, which are the basic
structures of the placenta, initially form by 4 or 5 weeks’ gestation.
he villi next to the decidua capsularis degenerate, forming the
chorion laeve. he villi contiguous with the decidua basalis
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