Accessories: The Placenta, Umbilical Cord and Amniotic Fluid
Jacques S. Abramowicz, MD
Dept. of Ob/Gyn and Fetal & Neonatal Medicine Center
Rush University Chicago
34th Annual Advanced Ultrasound Seminar
Orlando
February 17 – 19, 2011
The placenta
The umbilical cord
The amniotic fluid
Elements of complete examination
Location (normal, previa, abnormal site)
Implantation (normal vs. accreta in all its forms)
Thickness
Hemorrhages/Abruption
Tumors
Calcifications
Placental grading
Miscellaneous (circumvallate, velamentous cord insertion, vasa previa)
Abramowicz JS, Sheiner E: Ultrasound of the placenta: a systematic approach. Part I: Imaging. Placenta, 2008
Disclosure
I have no conflict of interest with respect to any of the material presented in this lecture. I am on the OB/Gyn advisory board of Philips and Siemens. I will not discuss off‐label or unapproved uses of drugs or devices.
The Placenta
Abnormal site implantation
Myoma
Septum
Synechia
Abnormal site implantation‐
complications
Spontaneous abortions
IUGR
Preterm labor
Placental abruption
Post‐partum hemorrhage
Placenta previa
No previa
Low‐lying (2‐3.5cm from internal os )
Marginal (edge 2cm or less from internal os)
Complete Diagnosis
Addominal us: 95% accuracy, 20% false +
Endovaginal: 97‐100% accuracy, 1‐2% false +
Accreta: when should you think about it?
Placenta accreta
1. Placenta accreta (placenta accreta vera): villi become attached to the myometrium. 2. Placenta increta: villi invade the myometrium. 3. Placenta percreta: trophoblast penetrates through the myometrium and into/through the peritoneum, sometimes extends to adjacent structures (bladder, bowels) Placenta previa
Previous cesarean delivery
Risk after 1CS: 4 fold increase
2CS: 11.3 RR increase
Risk after CS if previa: 5 fold increase Previous myomectomy or reconstructive uterine surgery Asherman's syndrome Multiparity
Advanced maternal age Submucous leiomyomata
Placenta accreta‐ sonographic findings
1. Irregularly shaped placental lacunae signs (vascular space). Sensitivity:93%, PPV: 93%
2. Obliteration of hypoechoic myometrial‐placental junction
3. Thinning of the myometrium overlying the placenta
4. increased vascularity of the uterine serosa‐bladder interface
5. Turbulent flow through the lacunae using Doppler studies
6. Protrusion of the placenta into the bladder
Placental abruption
The diagnosis is a clinical one and ultrasound is of limited value with a sensitivity of no more than 50% (Glanz et al. JUM, 2002; Oyelese et al. Obstet Gynecol, 2006)
Placental thickness and placental volume
Normal thickness: 2‐4cm
Central point or near cord insertion (when cord is centrally inserted)
Thick placenta
Diabetes
Isoimmunization
Infections (CMV, Syphilis, Toxoplasmosis)
Non‐immune hydrops
Partial mole
Turner syndrome
Placental mesenchymal dysplasia
Thrombophilias
Placenta in multiple gestations
25 weeks, NIH secondary to cardiac arrhythmia
Location Appearance
Chorioangioma next to
chorionic
surface
Placental “cystic” findings
Size
Blood flow
Clinical
Significance
Heterogeneous,
anechoic but may
contain mildly
echogenic material
(mucus)
variable hypervascular if >5cm, risk of
echofree (maternal
vessels),
appearance may
change
variable occasional,
turbulent,
slow
none, except if
associated with
placenta accrete
(see text)
NIH*, IUGR,
anemia, IUFD
Lakes
beneath
chorionic
plate
Subchorionic
fibrin
deposition
subchorio echogenic
nic
variable, no
usually
small
none
Intervillous
thrombosis
intraplace round, usually
ntal
anechoic
variable, no
usually
small
none, perhaps role
in isoimmunization
Cyst
subchorio echofree
nic
variable no
if >4.5cm, risk of
IUGR, IUFD
The Umbilical cord
Normal length: 60‐70cm, at term 3 vessels: 2 arteries, 1 vein
Abnormal length
Single umbilical artery
Knots
Cysts
Velamentous insertion
Vasa previa
Nuchal cord
Single umbilical artery
Abnormal length has been associated with fetal morbidity/mortality, but prenatal assessment is not possible
ƒApproximately 1% of all umbilical cords contain only one artery (left absent>right)
ƒ Many infants born with a single umbilical artery have no obvious anomalies
ƒ Single umbilical artery is associated with cardiovascular, GI, renal anomalies, in 15‐20% of cases
ƒ Trisomy 18 association
ƒ IUGR is a possible complication
ƒ Could be the result of genetic factors alone but environmental factors may also play a part (association with diabetes and maternal smoking during pregnancy)
Umbilical cord knots
•True knots versus false knots
• True knots occur in approximately 1% of pregnancies
• Associated with advanced maternal age, multiparity, and long umbilical cords.
• Highest rate in monoamnionic twins
• False knots (kinks in the umbilical cord vessels): more common and of no known clinical significance.
Velamentous insertion
¾ Cord inserts into the chorion laeve, away from the placental edge
¾ Vessels pass to placenta across surface of membranes between amnion and chorion
¾ 1% singletons and almost 15% monochorionic twins
¾ Ultrasonography: sensitivity= 67%; specificity= 100% (2nd trimester)
¾ Can cause hemorrhage if vessels are torn when membranes are ruptured (vasa previa)
¾ Associated with low birth weight, prematurity, and abnormal fetal heart patterns in labor
Vasa previa
ƒ Fetal vessels in the membrane in front of presenting part ƒ May occur with velamentous insertion or with vessels running to succenturiate lobe
ƒ May exist over dividing membrane when second twin has velamentous insertion
ƒ 1 per 2000‐3000 deliveries
ƒ Cause unknown
ƒ Color Doppler to visualize course of vessels, and pulse Doppler to confirm the fetal origin. Nuchal cord
ƒ One loop around the neck occurs in approximately 20% of cases ƒ Multiple loops occur in up to 5% of pregnancies
ƒ Can be detected using color Doppler ultrasound (sensitivity > 90%)
ƒ Rarely causes fetal demise and is not intrinsic reasons for intervention
Amniotic fluid‐Role
Amniotic fluid: too little, too much?
1. Lung development
2. Allows fetal movements (muscles, bones, joints)
3. Thermoregulator
4. Protects against infection
5. Protects fetus from trauma
6. Protects cord from compression
INF
LO
W
OUTF
LOW
GA (in weeks)
Volume (in CC)
10
30
16
190
22
500
28
700
32‐35
780‐1000
40
700
1
3
2
4
Dr. Mark Anthony performs AFI
Comparison of techniques
If AFI is gold standard
Guestimate to predict:
normal sensitivity: 96% specificity: 97%
Oligohydramnios
58%
83%
Polyhydramnios
100%
26%
AFI is better than single or 2 diameter pocket (Magann, 2000) AFI in multiple pregnancies
GA (weeks)
5th percentile
50th percentile
24
10
15
30
9
15
36
8
14
42
7
11
All techniques equivalent but single vertical pocket easiest and quickest, thus most clinically useful Moore and Cayle, 1990
Too little fluid
Definition
Estimated volume ,400cc (at term)
Max vertical pocket < 2cm
AFI < 5cm (8cm)
Two‐diameter pocket < 15cm2
Oligohydramnios
Oligohydramnios‐Doppler or not?
uid
uch fl
Too m
Definition
Single pocket>8cm
AFI>95th percentile (usually 20cm)
Polyhydramnios
Polyhydramnios‐Etiology
Idiopathic
Fetal anomalies
IDDM
Gestational DM
Multiple gestation
Other
66%
13%
8%
7%
5%
1%
Hill et al. 1987
Both polyhydramnios and oligohydramnios in the same pregnancy...
TTTS*
*Twin twin transfusion syndrome