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SON5023 Obstetrics > Topic 4 - Placenta, umbilical cord, cervix > Flashcards

Topic 4 - Placenta, umbilical cord, cervix Flashcards

1
Q

What is the standard of care to screen for risk of pre-term birth in a low risk population?

A

High quality cervical assessment at 20 weeks

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2
Q

What timing of cervical assessment is valuable high risk or pre-term birth?

A

Screening from 15 weeks

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3
Q

What are some interventions for managing a short cervix?

A

Progesterone and cervical cerclage

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4
Q

What is the primary role of sonographic evaluation of the cervix?

A

diagnosis of cervical incompetence in patients at risk who do not have a classic history.

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5
Q

What are the major risk factors for SPTB?

A 
Multiple gestation
Previous preterm delivery
Previous pre-term labour, term delivery
Abdominal surgery during pregnancy
Diethylstilbestrol exposure
Hydramnios
Uterine anomaly
History of cone biopsy
Uterine irritability
More than one second trimester abortion
Cervical dilation (>1cm) at 32 weeks
Cervical effacement (<1cm) length at 32 weeks
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6
Q

What are the minor risk factors for SPTB?

A 
Febrile illness during pregnancy
Bleeding after 12 weeks
History of pyelonephritis
Cigarette smoking (>10 per day)
One second trimester abortion
More than 2 first trimester abortions
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7
Q

What makes a woman high risk for SPTB?

A

More than one major risk factor indicates a HIGH risk

More than 2 minor risk factors also indicates a HIGH risk

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8
Q

What are the pitfalls of cervical assessment?

A

Distended bladder

False hourglass membrane

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9
Q

What causes false hourglass membrane?

A

Can be caused by a lower uterine segment contraction, low-lying hypoechoic fibroid or a large amount of fluid in the vagina
Can be excluded by a recognition of a closed internal os

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10
Q

What are some TAS findings that indicate TV follow up during cervical assessment?

A

Closed cervical length <25mm
Dilated cervical canal
Balloon fluid-filled lower segment with no visible cervix
Evidence of foetal cord or body part within the canal

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11
Q

What are some pitfalls of cervical TAS assessment?

A

Poor reproducibility of cervical TAS measurement
cervix may be obscured by the presenting part (especially cephalic)
empty bladder may reduce the quality of the measurement obtained
a full bladder may artificially elongate the cervix
Difficult to evaluate if cervix is less than 2cm due to vaginal and bladder tissue
Large maternal body habitus can limit visualization
Bowel gas can obscure visualization
Lower uterine segment myometrial contraction, immediately superior to the cervix, may result in a pseudoelongation of the cervix

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12
Q

How can you recognise pseudoelongation due to contraction?

A

artificially elongated length of the cervix (>5 cm)
thicker diameter of the “cervix” at the proximal extent
The thickness of the internal and external cervical os should be similar.
The transient nature of this appearance

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13
Q

How can you recognise pseudodilation due to contraction?

A

artificially elongated length of the cervix (>5 cm)
normal cervix lying caudal with respect to the pseudodilation
and the transient nature of this appearance.

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14
Q

What is the TVS cervical measurement criteria?

A

Place the probe in the anterior fornix of the vagina.
Obtain a sagittal view of the cervix, with the long-axis view of echogenic endocervical mucosa along the length of the canal.
Withdraw the probe until the image is blurred, and reapply just enough pressure to restore the image (to avoid excessive pressure on the cervix, which can elongate it).
Enlarge the image so that the cervix occupies at least two-thirds of the image and external and internal os are well seen.
Measure the cervical length from the internal to the external os along the endocervical canal.
If the canal is curved use two straight lines
Obtain at least three measurements, and record the shortest best measurement in millimeters.

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15
Q

How does the endocervical canal appear on sonography?

A

as an echogenic line surrounded by a hypoechoic zone

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16
Q

What is the definition of a short cervix?

A

Short cervix is defined as less than 25mm
Less than 26mm = 10th centile
Less than 13mm = 1st centile

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17
Q

What is the only important measurement of the cervix?

A

Functional length. Funnel length, width not imprtant

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18
Q

What are abnormal cervical findings on TVS?

A 
Shot cervix
funnelling
Positive response to fundal pressure
Presence of amniotic fluid sludge
shortening of 8-10mm since previous TVS
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19
Q

Why is the rate of cervical change important?

A

A “short and shortening” cervical length may be a more effective tool for SPTB prediction than a “short but stable” cervical length.
Serial cervical shortening in the second trimester may identify patients with true mechanical failure of the cervix, who may benefit from the placement of a cerclage to prevent SPTB.

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20
Q

What is dynamic cervical change?

A

spontaneous shortening, lengthening, or funneling observed during real-time TVS

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21
Q

What sonographic features are associated with an increased risk of PTB independent of cervical length

A

canal dilation
absence of the glandular area along the length of the canal
amniotic fluid debris

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22
Q

What is cervical incompetence?

A

defined as the inability to support a full-term pregnancy because of a functional or mechanical defect of the cervix

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23
Q

What is cervical incompetence characterised by clinically?

A

clinically by acute painless dilation of the cervix usually in the mid-trimester, culminating in prolapse and/or PPROM (preterm pemtrure rupture of membranes) with resultant preterm delivery.

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24
Q

What is SPTB defined as?

A

delivery earlier than 34 weeks’ gestation

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25
Q

What are the two different mechanisms of cervical incompetence?

A

Functional and menchanical

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26
Q

What characterises functional failure of the cervix?

A

premature cervical ripening
(shortening and dilation normally occurring at the end of gestation)
most often is related to urogenital or intrauterine infection or inflammation
low risk of recurrence

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27
Q

What characterises mechanical failure of the cervix?

A

defect in the structural integrity of the cervix
may result from traumatic injury to the cervix
including cervical laceration, amputation, conization, excessive cervical dilation before diagnostic curettage, or therapeutic abortion.

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28
Q

What are the indications for cervical cerclage?

A

History indicated (prophylactic) cerclage: in patients with unexplained second-trimester delivery in the absence of labor or abruptio placentae.

Physical examination indicated (“rescue”) cerclage: in patients presenting with advanced cervical dilation in the absence of labor or abruptio placentae.

Sonographic finding of a short cervix (<25 mm) before 24 weeks of gestation in patient with singleton pregnancy and prior history of PTB less than 34 weeks of gestation.

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29
Q

What is fetal fibronectin (FFN)?

A

a glycoprotein that binds the amniochorion to the decidua and is released into cervicovaginal fluid in response to inflammation or separation of amniochorion from the decidua

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30
Q

Why is FFN important?

A

Risk of SPTB remains low in women with cervical length of 30 mm or more and in those with cervical length of between 15 and 30 mm and negative FFN

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31
Q

What are the risks of SPTB before 34 weeks’ gestation of sonographic markers?

A

if the cervix measured less than 30 mm, risk increased by 2.0-fold if measured before 20 weeks
increased by 2.3-fold after 20 weeks
presence of funneling, regardless of gestational age, increased the likelihood ratio to 4.7-fold
a TVS cervical length of longer than 30 mm makes the diagnosis of preterm labor extremely unlikely

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32
Q

What is the role of the placenta?

A

provides oxygen and nutrients to the foetus, removes waste products from its blood, secretes hormones and attaches the foetus to the uterine wall. Gas exchange, metabolic transfer, endocrine function, drug transfer.

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33
Q

What is the structural unit of the placenta?

A

chorionic villus.

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34
Q

What should you look at when evaluating the placenta sonographically?

A

shape, size, location and echotexture

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35
Q

Comment on normal calcification of the placenta

A

During the first 6 months, calcification is microscopic

Macroscopic calcification occurs in the 3rd trimester, commonly after 33 weeks

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36
Q

What causes premature or accelerated calcification of the placenta?

A

Maternal cigarette smoking

Patients with thrombotic disorders treated with heparin or aspirin prophylactics

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37
Q

How thick should the placenta be?

A

No more than 40mm at term

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38
Q

What might a thin placenta indicate?

A

IUGR

39
Q

What might a thick placenta indicate?

A

Heterogeneous and thick placenta:
Molar pregnancy
Triploidy (partial mole)
Placental haemorrhage

Homogeneous and thick placenta:
Gestational diabetes
Anaemia
Hydrops
Infection (villitis)
Aneuploidy
40
Q

What might large placental lakes indicate?

A

(>5 cm in largest dimension) have been associated with IUGR

41
Q

What does placental infarction look like?

A

hypoechoic lesions with echogenic borders

42
Q

What can circumvallete placentas be confused with?

A

can also be confused with uterine synechiae, uterine septum, and amniotic bands.

43
Q

What is the 3D sono sign for circumvallate placenta?

A

“tire mounted on a wheel”

44
Q

What are complete circumvallate placentas associated with?

A 
Placental abruption
Pre-term delivery
Oligohydramnios
IUGR
Emergency C-section
Apgar score <7
Perinatal death
45
Q

Is partial circumvallate placenta significant?

A

no, they are common

46
Q

What is a succenturiate lobe?

A

Accessory lobe of the placenta

47
Q

What are some risks associated with succenturiate lobes?

A

There must be an arterial and venous connections to the main portion of the placenta- this must be identified (vasa previa)
Issues will arise when the accessory lobe is left after delivery
Can cause placenta previa/vasa previa

48
Q

What are some risks of bi lobed placenta?

A

Umbilical cord may insert between the membranes

Poses a similar risk to succenturiate lobes

49
Q

What are some risk factors of amnion-chorion separation?

A

Previous amniocentesis is a risk factor for amnion-chorion separation
Associated factors may include IUGR, preterm delivery, oligohydramnios, placental abruption, and Down syndrome

50
Q

What is the hallmark of placenta previa in the second and third trimesters?

A

Bleeding in the second and third trimesters

51
Q

What are the different types of placenta previa?

A

Complete placenta previa - the internal cervical os is totally covered by the placenta
Marginal placenta previa denotes placental tissue at the edge of, or encroaching on, the internal cervical os.
A low placenta is one in which the placental edge is within 2 cm, but not covering any portion, of the internal cervical os

52
Q

What are some risk factors for placenta previa?

A

number of prior cesarean deliveries
increasing parity independent of number of prior cesarean deliveries
increasing maternal age

53
Q

What does maternal floor infarction appear as sonographically?

A

hyperechoic placental mass
or placental thickening.
Hyperechoic areas of the placenta are especially prominent along the maternal surface
can be a normal findingwith mature placentas.
Subchorionic cysts are also commonly present with maternal floor infarction
basal plate calcifications can be quite prominent
The hyperechoic mass seen with maternal floor infarction resembles that seen with placental chorioangiomas

54
Q

What are some associations of infarctions?

A 
Both abnormalities are associated with;
Oligohydramnios
umbilical artery Doppler abnormalities
 IUGR
central nervous system injury
fetal demise.
55
Q

Comment on the significance of placental infarctions

A

peripheral infarctions are common at term
infarctions larger than 3 cm or involving more than 5% of the placenta are associated with increased perinatal morbidity.
Both maternal and fetal thrombophilias can lead to placental infarctions

56
Q

What are some solid placental masses?

A

Chorioangioma
subamniotic hematoma
subchorionic hematoma
placental hemorrhage.

57
Q

Comment on the significance of sub chorionic placental cysts

A 
predominantly innocuous finding
Larger cysts (>4.5 cm) are associated with IUGR.
Maternal floor infarction may also be associated with placental cysts
58
Q

Comment on the significance of chorioangioma

A

most common benign tumor of the placenta
most are asymptomatic
large chorioangiomas (>5cm) can lead to high-output fetal cardiac failure, anemia, hydrops, and death.

59
Q

What is the sonographic appearance of chorioangioma?

A

well-circumscribed solid tumors in the placenta
hypoechoic to hyperechoic
threshold of 5 cm high risk for adverse outcome
color or power Doppler ultrasound is helpful to identify increased blood flow within the solid mass, thereby distinguishing the mass as a chorioangioma
Blood flow is not consistently demonstrable
those with low flow tend to have a better outcome

60
Q

What is the sonograhic hallmak of Mesenchymal dysplasia of the placenta?

A

described as having a “stained-glass” appearance when color Doppler sonography is used, due to the flow noted in the multiple placental cysts

61
Q

What may Mesenchymal dysplasia of the placenta be mistaken for?

A

partial hydatidiform mole

62
Q

What is mesenchymal dysplasia of the placenta associated with?

A

may be associated with a normal fetus, although IUGR is common.
also an association with Beckwith-Wiedemann syndrome
The karyotype is usually normal.

63
Q

Comment on the significance of large chorioangiomas

A

There is a 30% maternal or fetal complication rate.
Complications include polyhydramnios, congestive heart failure/cardiomegaly, fetal death, preterm labour, IUGR, preeclampsia, anemia, and congenital anomalies.
Heart enlargement and failure occur as a result of the arteriovenous shunting from the tumour or hemolysis leading to anemia.
Careful attention must be directed towards the fetus to ascertain whether there are any sonographic clues to fluid overload or hydrops (see later).
If none are found, serial sonography should be performed every 2-3 weeks.

64
Q

What do abnormalities of the retroplacental space appear as?

A

Absence of the hypoechoic space may be seen in placenta percreta.
A hypoechoic space > 1-2 cm may be seen in case of a contraction or a retroplacental haemorrhage.

65
Q

What is placenta accrete?

A

A placenta that is abnormally adherent to the uterine wall after delivery is termed placenta accreta.
Placenta increta - invades the myometrium more deeply
placenta percreta - in part protrudes through the uterine serosa.
serious complication of pregnancy associated with maternal blood loss, need for hysterectomy, and retained products of conception.

66
Q

What does placenta accrete look like on ultrasound?

A

A placenta that is abnormally adherent to the uterine wall after delivery is termed placenta accreta.
Placenta increta - invades the myometrium more deeply
placenta percreta - in part protrudes through the uterine serosa.
serious complication of pregnancy associated with maternal blood loss, need for hysterectomy, and retained products of conception.

67
Q

What is the clinical presentation of placental abruption?

A

Patients typically present with third-trimester vaginal bleeding associated with abdominal or uterine pain and labor

68
Q

What are some risk factors for placental abruption?

A 
History of prior abruption
Hypertension
prolonged rupture of membranes
UGR
Chorioamnionitis
Polyhydramnios
maternal thrombophilias
maternal substance use (tobacco, alcohol, cocaine)
 maternal trauma
advanced maternal age
69
Q

What is the sonographic appearance of placental abruption?

A

diagnosis typically made based on clinical findings
the retroplacental clot is frequently isoechoic
cannot always be identified sonographically
An indirect sign of the presence of an acute hematoma is apparent thickening of the placenta, which is associated with worse outcome.

70
Q

A 32 year old patient is referred for ultrasound. She is 29 weeks pregnant and had an episode of bleeding. The bleeding has settled completely by the time that you perform the ultrasound. Can you think of the main causes for antepartum haemorrhage (APH) in the third trimester?

A

The important causes of antepartum haemorrhage that you want to exclude on ultrasound are placenta previa and abruption/retroplacental haemorrhage.
Usually the clinical history is very different for these two scenarios but some overlap may occur.
Placenta previa
causes painless blood loss.
Because the bleeding only just stopped, probably the translabial technique is more appropriate than the transvaginal technique to assess for placenta previa. Cervical dilatation can also be a cause of (usually minor) blood loss.
Abruptio placenta is an acute clinical syndrome manifested by pain, vaginal bleeding and uterine tenderness.
Hypovolemic shock can occur, necessitating rapid delivery.
Often there is no time for ultrasound.
In patients who are sufficiently stable to have ultrasound, an ill-defined echogenic collection, either hyperechoic or isoechoic with respect to the placenta is seen in the retroplacental area.
While you do a scan for antepartum haemorrhage, it is a good idea to look at fetal well-being.

71
Q

What are some anomalies of the umbilical cord?

A 
Tumours
Haemangiomas
Haematomas
Varices
Aneurysms
Teratomas
Cysts
72
Q

What are some associations of abnormally long umbilical cords?

A

associated with asphyxia or death resulting from a variety of situations that compromise cord flow, including excessive coiling, true knots, multiple loops of nuchal cord, and cord prolapse

73
Q

What are some associations of abnormally short umbilical cords?

A

associated with conditions that impair fetal movement early in gestation, such as akinesia syndromes, aneuploidy, and extreme IUGR

74
Q

What is absent coiling associated with?

A

associated with single umbilical arteries, multiple gestations, fetal demise, preterm delivery, aneuploidy, and both marginal and velamentous umbilical cord insertions
Lower degrees of coiling are associated with lesser degrees of fetal growth

75
Q

What is a sonographic sign of an umbilical knot?

A

Hanging noose sign

76
Q

What are some associations of 2nd and 3rd trimester cord cysts?

A

associated with both structural and chromosomal defects
Trisomies 13 and 18 are the most common chromosomal abnormalities associated with umbilical cord cysts
genitourinary and gastrointestinal anomalies are the most common structural defects

77
Q

What is the most common umbilical cord tumour?

A

most common is the umbilical cord hemangioma

appears as a heterogeneous mass surrounded by multiple peripheral cystic areas

78
Q

What makes nuchal cord significant?

A

Multiple tight loops of nuchal cord indenting the skin late in the third trimester may prompt further evaluation but management is unclear

79
Q

What umbilical cord abnormality is vasa previa associated with?

A

Velamentous cord insertion

80
Q

What is the significance of velamentous cord insertion?

A

the unprotected vessels may bleed in the antenatal period.
With the vessels in the membranes, no Wharton jelly is present, leading to increased risk of compression or even rupture of these vessels.
Associated with IUGR, Pre-term delivery, Congenital anomalies, Low Apgar score, Neonatal death

81
Q

What are the two situations vasa previa may occur?

A

a velamentous cord insertion as mentioned above which the membranous fetal umbilical vessels can traverse the internal cervical os
a succenturiate lobe on the opposite side of the internal os from the main placenta.

82
Q

List adnexal pathology during pregnancy

A 
hyperstimulated ovaries
ovarian hyperstimulation syndrome
theca lutein cysts
hyperreactio luteinalis
the rare luteoma of pregnancy
 Most are related to the normal or abnormal response to serum hCG levels.
83
Q

What are hyperstimulated ovaries?

A

a normal response to elevated circulating levels of hCG
most common in women undergoing ovulation induction
the ovaries are enlarged with multiple cysts

84
Q

What is a risk of hyperstimulated ovaries?

A

Torsion

85
Q

What is ovarian hyperstimulation syndrome?

A

when the hyperstimulation is accompanied by fluid shifts

86
Q

What is mild OHS?

A

associated with lower abdominal discomfort
no significant weight gain
ovaries are enlarged, but less than 5 cm in average diameter.

87
Q

What is moderate OHS?

A

presents with weight gain of 5 to 10 pounds
ovarian enlargement 5 to 12 cm
patient may have nausea and vomiting

88
Q

What is severe OHS?

A

weight gain of more than 10 pounds
typically severe abdominal pain and distention.
The ovaries are greatly enlarged (>12 cm in diameter)
contain numerous large, thin-walled cysts, which may replace most of the ovary.
The associated ascites and pleural effusions may lead to
depletion of intravascular fluids and electrolytes
resulting in hemoconcentration with hypotension, oliguria, and electrolyte imbalanceevere

89
Q

What are theca lutein cysts?

A

largest of the functional ovarian cysts
associated with high hCG levels
occur in patients with gestational trophoblastic disease
not seen in first-trimester diagnosis of gestational trophoblastic disease, because the hCG level will not have been sufficiently high for a long
can also be seen in OHS as a complication of drug therapy for infertility

90
Q

What does theca lutein cyst look like sonographically?

A

Bilateral
Multilocular
very large
may undergo hemorrhage, rupture, and torsion

91
Q

What is hyperreactio luteinalis?

A

caused by an abnormal response to circulating hCG in the absence of ovulation induction therapy
60% with normal circulating levels of hCG
usually occurs in the third trimester
majority of patients are asymptomatic, although maternal virilization may be seen in up to 25% of patients
polycystic ovarian disease increases likelihood

92
Q

What is the sonographic appearance of hyperreactio luteinalis?

A

bilaterally enlarged ovaries with multiple cysts similar to OHS
the ovaries tend not to be as large
occurs later in pregnancy.

93
Q

What is a luteoma of pregnancy?

A

only solid mass in this group of pregnancy-related processes
very rare benign process unique to pregnancy
Most patients are asymptomatic, although maternal virilization may occur in up to 30%
50% risk of virilization of the female fetus

94
Q

If you suspect vasa previa what should yo do?

A

spectral Doppler should be placed on these vessels to confirm that they are fetal.

SON5023 Obstetrics (9 decks)

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