sonographic abnormalities of the placenta and...
TRANSCRIPT
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Sonographic Abnormalities of
the Placenta and Umbilical Cord
Ivana M Vettraino, MD, MBA
Maternal Fetal Medicine
Associate Professor, Michigan State University
Here, There and Everywhere
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Objectives
• Understand development of the placenta and umbilical cord
• Recognize the prenatal sonographic appearance of common and uncommon placental abnormalities
• Recognize the prenatal sonographic appearance of common and uncommon umbilical cord abnormalities
• Understand which additional specific sonographic images to obtain following identification of a suspected placental or umbilical cord abnormality during prenatal sonogram
• Identify those patients at risk for placental abnormalities
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Introduction
Placenta
Transfer site for oxygen, carbon dioxide, and
building blocks for the fetus
Synthesizes many proteins and other
subsances
Umbilical cord
Conduit for oxygenated and non-oxygenated
fetal blood to the placenta
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Placental DevelopmentBegins at implantation (Day 5 to 6 post
fertilization)
Embryonic pole of blastocyst contacts uterine
epithelium
Outer cell layer (Trophoblast) becomes the placenta
Inner cell layer (Extraembryonic (EE) mesodermal
cells)
Day 13 post fertilization
Formation of placental villi begins
Outgrowths of trophoblast proliferate laterally into the
IVS
Trophoblast shell gradually breaks open allowing
maternal blood to enter the placental lacunae
Known as ‘‘hemochorial placentation”
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Placental Development
Summary
Villi form over the entire chorionic sac
By end of the first trimester
Villi regress from all except the deep pole
Chorion levae
Remain as the definitive discoid placenta
Chorion frondsum
The decidua
Abnormalities in this process result in persistence of villi at abnormal sites on the chorionic sac
Accessory or succenturiate lobes
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Ultrasound
As early as 10 weeks’ gestation
Placenta visible
Thickening of the hyperechoic rim around gestational
sac
12 to 13 weeks’ gestation
Intervillous blood flow can be seen by color Doppler
14 to 15 week’s gestation
Placenta seen as hypoechoic area
Retroplacental complex
Decidua
Myometrium
Uterine vessels
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The Early Sonogram
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The Early Sonogram
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The Early Sonogram
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The Early Sonogram
The exocoelomic cavity (ECC)
The space between the trophoblast/chorion and the amnion/yolk sac
Large fluid-filled space
Ultrasound
Visible using a transvaginal probe toward end of third week post fertilization (fifth week of menstrual age)
Between 5 and 9 weeks of pregnancy represents largest anatomic space within the chorionic sac
By the end of 3rd month
Amnion abuts the inner surface of the chorion
ECC is obliterated
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The Early Sonogram
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The Early Sonogram
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The Early Sonogram
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The Early Sonogram
Non-fusion of the
amnion/chorion
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The Placenta
Term placenta
Discoid - 15 to 20 cm in diameter
Ovoid at high altitude
3 cm at the center
Should not be thicker than 4 cm at term
(Thickness in mm = to gestational age in weeks)
500 grams in weight
Size is a reflection of the health and size of the fetus
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Placental Disc
Thin placenta (placentomalacia)
Associations
Small for gestational age fetus
Intrauteirne infection
Chromosomal abnormalities
Severe polyhydramnios
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Placental Disc
Thick placenta (Placentomegaly)
Technical artifact
Small area of attachment to the uterine wall
Heterogenous
Molar pregnancy
Triploidy
Placental hemorrhage
Homogenous
Maternal diabetes
Fetal Anemia
Hydrops
Infection
Chromosomal abnormalities
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Normal Placenta
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Placental Disc
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Placental Disc
Circumvallate placenta
Abnormality of placental shape
Membranes insert toward the center of the placenta
Rolled, thickened membranes
Complications
Hemorrhage
Infarction
Abruption
Fetal growth restriction
Preterm laor/delivery
May be partial or complete
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Circumvallate Placenta
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Circumvallate Placenta
Uterine
Synechiae
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Circumvallate Placenta
Uterine Synechiae
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Circumvallate Placenta
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Circumvallate Placenta
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Circumvallate Placenta
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Decision Tree
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Placental Disc
Circumvallate placenta
Sonographic appearance
Irregular rolled up edge of placenta
Appears like a shelf or band
Can be confused with a uterine synechiae
Upturned edge may contain hypoechoic or
cystic spaces
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Placental Disc
Placental calcifications
No proven correlation with pregnancy outcome
Etiologies
Maturation
Grading of the placental no longer in vogue
Maternal tobacco use
Maternal thrombotic disorders on anti -coagulation therapy
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Placental Calcifications
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Placental Calcifications
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Placental Infarcts
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Placental Disc
Succenturiate (accessory) lobe
Associations
Infarction
Velamentous cord insertion
Vasa previa
Must assess where fetal vessels connect to the main body of the placenta
Color Doppler can be useful
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Placental Disc
Succenturiate/Accessory Lobes
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Placental Disc
Succenturiate/Accessory Lobes
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Caution
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Placental Masses
Placenta tumors
Chorioangioma
Most common benign tumor
Vascular mass arising from chorionic tissue
Small tumors found in 1 % of examined placentas
Most clinically relevant mass (greater than 5cm)
1 in 500 to 1 in 16,000 live births
Complications
None
Fetal hydrops from high output cardiac failure due
to “steal” phenomena
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Placental Masses
Placenta tumors
Chorioangioma
Sonography
Well-circumscribed round mass near chorionic
surface
Often near umbilical cord insertion
Sonographic measures
MCA Doppler
Evaluation for fetal hydrops
Serial sonograms every 2 to 3 weeks to assess
the fetus if mass around 5 cm
More often if larger
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Placental Masses
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Placental Masses
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Placental Masses
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Placental Masses
Placental infarct 21 ½ weeks’
gestation
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Placental Masses
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Placental Mass
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Placental Mass
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Placental Masses• Lakes
• Enlarged spaces filled with maternal blood
• Appear nearly black
• Slow swirling blood seen within the spaces
• Considered a normal finding
• Can be associated with IUGR
• Can mimic molar pregnancy
• Caution with history of previous uterine surgery
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Placental Cysts
• Most surface cysts associated with normal
pregnancy outcome
• Related to cystic change in an area of
subchorionic fibrin
• Cysts larger than 4.5 cm or more than 3 in
number are associated with intrauterine
growth restriction
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Placental Cyst
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Placental Abruption
A clinical diagnosis - not an ultrasound
diagnosis
Premature separation normally implanted
placenta
Associations
Maternal hypertension
Preeclampsia
Abdominal trauma
Cocaine abuse
Tobacco use
Advanced maternal age
Male fetus
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Placental Abruption
SonographyHemorrhage
Acute - hyperechoic
3 to 7 days - isoechoic
1 to 2 weeks - hypoechoic
Greater than 2 weeks - complex appearance
Retroplacental hypoechoic area
Must distinguish from complex of uteroplacental vessels
Should be less than 1 to 2 cm in thickness
Can be confused with a myoma or uterine contraction
Color Doppler interrogation useful
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Placental Abruption
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Subchorionic Bleed
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Placental Hemorrhages
AJR 2001; 176:607-615
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Sub-Amniotic Bleed
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Placenta Previa
Placenta over the internal cervical os
Primary cause of third trimester bleeding
0.5 to 1 percent of term pregnancies
Risk factors
Advanced maternal age
Multiparous patients
History of cesarean section
History of uterine curretage
Low-lying placenta
Placental edge witin 2 cm from the internal cervical os
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Placenta Previa
Sonography
Transabdominal scanning
Artifact from distended bladder
Artifact from localized uterine cramp
25 percent of placental location incorrectly noted
Translabial scanning
Reliable for placenta ≥ 2 cm from internal cevrical os
Less reliable for placenta ≥ 1 cm from internal
cervical os
Transvaginal scanning
No contraindication
Probable gold-standard
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Artifact Of Full Bladder
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Placenta Previa
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Low-lying Placenta
Sonography
Second trimester
Very common
Only 1 to 5 percent persist into 3rd
trimester
Translabial scanning
Transvaginal scanning
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Low-lying Placenta
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Placenta Accreta
Abnormal adherence of placenta to uterus resulting
in failure to separate following delivery
Three categories
Accreta
Increta
Percreta
Prevalence
1 in 2500 pregnancies
1 in 10 with placenta previa
Risk factors
Prior cesarean section
Advanced maternal age
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Placenta Accreta
Sonography
Findings
Retroplacental hypoechoic area is absent
Prominent multiple lacunae within the placenta
“Swiss cheese” appearance
Marked periplacental vascularity on color Doppler interrogation
Transvaginal sonogram with power Doppler should be considered in cases of an anterior placenta in patients at risk
MRI can be helpful in suspcious cases or in cases with a posterior placenta
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Placenta Accreta
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Placenta Accreta
Ultrasound Obstet Gynecol 2005; 26: 89–96.
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Placenta Accreta
J Ultrasound Med 22:19-23 • 0278-4297
Gestational sac with low implantation
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The Umbilical Cord
1. Ductus omphalo-entericus
2. Allantois
3. Umbilical Vein
4. Umbilical arteries
5. Amnion
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The Umbilical Cord
Lifeline between the fetus and
placenta
Formed by the fifth week of
development
Protects the vessels that travel
between the fetus and the placenta
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The Umbilical Cord
EmbryologyBy end of 3rd week of development embryo attached to placenta by a connecting stalk comprosed of 5 structures
By the end of 1st trimester structures disappear
• Omphalo-enteric duct (Meckel's diverticulum)
• Umbilical vesicle of the allantois (Umbilical ligament)
• Vitelline circulation system in the extra-embryonic region
• Umbilical coelom, which clumps and disappears
Resulting in 2 arteries and 1 vein surrounded by an amniotic epithelial layer
Warton jelly forms as connective tissue of the body stalk and the amnion
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The Umbilical Cord
Normally contains two umbilical arteries and one
umbilical vein
Approximately 1% of all umbilical cords contain
only one artery–rather than the normal two
Associations
Variation of normal
Cardiovascular anomalies in 15-20%
Renal anomalies
SGA baby
Maternal smoking during pregnancy
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Single Umbilical Artery
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3 versus 2 vessel Umbilical
Cord
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The Umbilical Cord
Other pathologies
Mid-gut herniation
Loops of bowel found within the proximal
portion of the cord between 10 to 13 weeks’
Meckel’s diverticulum
Intrinsic processes
Inflammation, knots and torsion
Extrinsic damage
Following invasive, diagnostic procedures
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The Umbilical Cord
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The Umbilical Cord
Placental insertion variations
Central insertion
Most common
Marginal insertion (Very edge of placenta)
Approximately 7% of single births
“Battledore”
Velamentous insertion
Fetal vessels course through membranes before entering placenta
Approximately 1% of pregnancies Associated with fetal growth restriction
Vasa previa
Vessels course near or over the internal cervical os
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The Umbilical Cord
Pathologies of the umbilical cordLength
Normal length - 50 and 60 cm with a diameter of 1.5 cm
Can be too short (seldom) or too long (more prevalent)
Placental cord insertion
Velamentous, marginal or eccentric
Number of vessels
Normally contains two arteries and a vein
Single umbilical artery
One newborn per 200 births
Associated with cardiac and renal anomalies as well as fetal growth restriction
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Images
Velamentous cord insertion
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The Umbilical Cord
Pathologies of the umbilical cordLength
Short cord
Increase risk of congenital anomalies, trisomy 21, oligohydramnios, breech presentation
Abnormally long cords
Knots
True
False
Nuchal cords
25 percent of pregnancies
Two or more are worriesome
Cord prolapse
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Umbilical Cord
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The Umbilical Cord
Pathologies of the umbilical cord
Coiling
Absence
4 % of fetuses
Associated with increase perinatal
morbidity and mortality
Increase risk of trisomy 21, velamentous
cord insertion, coarctation of the aorta,
intrauterine death, preterm birth
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The Umbilical Cord
Pathologies of the umbilical cord
Cysts
3.4 percent of 1st trimester fetuses
Associated with fetal anomalies and aneuploidy
50 percent of cases
Sonographically
True cysts
Encircled by color Doppler blood flow
Pseudocysts
Due to areas of focal edema within the Warton’s
jelly
Do not have peripheral blood flow
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Umbilical Cord Varix
http://www.fetalultrasound.com/online/text/34-023.htm
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Umbilical Cord Varix
http://www.centrus.com.br/DiplomaFMF/SeriesFMF/doppler/capitulos-html/chapter_13.htm
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Vasa Previa
Rare but life threatening to the fetus
Fetal vessels cross over or near the internal
cervical os
High index of suspcion necessary
Velamentous cord insertion
Accessory/succenturiate lobe
Resolution of a placenta crossing the
internal cervical os
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Vasa Previa
Sonography
Index of suspicion
Color Doppler
Must distinguish from free loops of umbilical
cord over the cervix
Re-examine patient at a later time
Note that the cord is free floating and moves
away from the cervix with change in
maternal position
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Images
Vasa Previa
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Vasa Previa
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The Umbilical Cord
• Diagnostic utility of the umbilical cord
• Noninvasive methods to assess fetal well-being
• Assessment of fetal blood flow through umbilical cord
• Doppler interrogation of the umbilical artery
• Measuring amount of forward blood flow through the umbilical artery during fetal systole and diastole
• More forward blood flow from the fetus to the placenta through the umbilical artery, the healthier the fetus
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Miscellaneous
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Amniotic band
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