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LMC Ultrasound > OB Ch 55-57 > Flashcards

OB Ch 55-57 Flashcards

1
Q

What are the fetal membranes comprised off

A
  • Chorion
  • Amnion
  • Allantos
  • Yolk sac
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2
Q

Chorionic plate

A

The fetal surface of the placenta

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3
Q

Basal plate

A

The maternal surface of the placenta

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4
Q

Chorion frondosum

A

Forms the fetal part of the placenta and contains the villi

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5
Q

Chorion laeve

A

The nonvillious part of the chorion around the gestational sac

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6
Q

Decidua basalis

A

Decidua reaction that occurs between the blastocyst and the myometrium

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7
Q

Decidua capsularis

A

Decidua reaction that occurs over the blastocyst closest to the endometrial cavity

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8
Q

Decidua vera (parietalis)

A

Decidua reaction except for the areas beneath and above the implanted ovum

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9
Q

Functions of the placenta

A
  • Respiration
  • Nutrition
  • Excretion
  • Protection
  • Storage
  • Hormonal production
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10
Q

What is the major functioning unit of the placenta?

A

Chorionic villus

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11
Q

Velamentous placenta

A

Refers to the insertion of the umbilical cord that inserts on the membranes

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12
Q

Battledore placenta

A

Refers to the insertion of the umbilical cord at the margin of the placenta, within 10 mm of the edge

Labor may cause the cord to prolapse or be compressed during contractions

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13
Q

Weeks that the chorion and amnion fuse together

A

16th week

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14
Q

How big is the yolk sac

A

.8 mm

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15
Q

Function of hCG

A
  • Causes the uterine endometrium to convert to decidua, a glycogen rich mucosa that nourishes the early pregnancy
  • Keeps the corpus luteum functioning, so that the corpus luteum continues to produce estrogen and progesterone
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16
Q

Primary cause of placentomegaly

A

Maternal diabetes and Rh incompatibility

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17
Q

Common site of fibrin deposits

A

Appears as hypo echoic areas beneath the chorionic plate of the placenta

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18
Q

Complications of previa

A
  • Preterm delivery
  • Maternal hemorrhage
  • Increased risk of placental invasion
  • Increased risk of postpartum hemorrhage
  • IUGR
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19
Q

Three placental invasions

A
  • Percreta
  • Increta
  • Accreta

*Penetrates beyond the endometrial lining of the uterus

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20
Q

Placenta percreta

A

Penetration of the chorionic villi through(per-) the uterus

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21
Q

Placenta increta

A

Further extension of the chorionic villi into (in-) the myometrium

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22
Q

Placenta accreta

A

The chorionic villi attach to the myometrium without muscular invasion.
-Occurs in 1 to 2500 deliveries

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23
Q

Circumvallate

A

Attachment of the placenta membranes to the fetal surface of the placenta rather than to the underlying villous placental margin
-Occurs in 1-2% of pregnancies

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24
Q

Succenturiate

A

The presence of one or more accessory lobes connected to the body of the placenta-by-placenta vessels.

  • Occurs in 3-6% of pregnancies
  • Lobes develop infarcts and necrosis
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25
Q

Placental abruption

A

Refers to the separation of a normally implanted placenta prior to term delivery

  • Occurs in 1 in 120 pregnancies
  • Bleeding into the decidua basalis
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26
Q

Types of abruption

A
  • Retroplacental abruption

- Marginal abruption

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27
Q

Retroplacental abruption

A

Results from the rupture of spiral arteries and is a “high pressure” bleed. Associated with hypertension and vascular disease.
-Hematoma is between the placenta and uterus

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28
Q

Marginal abruption

A

Most common type; also known as subchorionic bleeds.
Results from tears of the marginal veins and represents a “low pressure” bleed.
Hemorrhage arises from the edge of the placenta, dissects beneath the placental membranes
Associated with little placental detachment

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29
Q

Marginal previa

A

Does not cover the os, but its edge comes to the margin of the os

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30
Q

Complete previa

A

The cervical internal os is completely covered by placental tissue
-20% of patients

31
Q

Partial previa

A

Only partially covers the internal os

32
Q

Low-lying placenta

A

Is implanted in the lower uterine segment, its edge does not reach the internal os

33
Q

Maternal conditions that cause small placenta

A
  • IUGR
  • Intrauterine infection
  • Aneuploidy
34
Q

Vasa previa

A

Potentially life-threatening fetal complication that occurs when large fetal vessels run in the fetal membranes across the cervical os.
-Occurs in 1 of 2500 deliveries

35
Q

Two common causes of vasa previa

A
  • Velamentous insertion of the umbilical cord into placental membranes
  • When a succenturiate lobe is present and the connecting vessels traverse the cervix
36
Q

Most common benign vascular tumor of the placenta

A

Chorioangioma

-1% of pregnancies

37
Q

Umbilical cord knots

A
  • True knots

- False knots

38
Q

True knots of the umbilical cord

A

Arise from fetal movements and are more likely to develop during early pregnancy when relatively more amniotic fluid is present.
Associated with advanced maternal age, multiparity, and long umbilical cord

39
Q

False knots of the umbilical cord

A

Seen when the blood vessels are longer than the cord. Folded on themselves and produces nodulations on the surface of the cord

40
Q

Nuchal cord

A

Most common cord entanglement in the fetus, seen around the fetal neck

  • Single loop 20% of deliveries
  • Two loops 2.5%
41
Q

What might a single umbilical artery by caused from

A

Atrophy of one of the umbilical arteries in the early development stage
Associated with congenital anomalies in 20-50% of cases

42
Q

Cord prolapse

A

Occurs when the cord lies below the presenting part. Exist when presenting part does not fit closely and fails to fill the pelvic inlet

43
Q

Short cord

A

<35 cm in length

may predispose the fetus to inadequate descent, cord compression, fetal distress, and oligohydraminos

44
Q

Long cord

A

> 80 cm in length

45
Q

Coiling of the umbilical cord

A

Normal and related to fetal movement. May coil as many as 40 times, usually to the left and near the fetal insertion site

46
Q

Thrombosis is more common in which umbilical vessel

A

Umbilical vein

47
Q

How is the cord formed

A

Forms during the first 5 weeks of gestation. Fusion of omphalomesenteric (yolk sac) and allantoic ducts

48
Q

Length of the umbilical cord in the first trimester

A

Same length as the CRL

49
Q

Omphalomesenteric cyst

A

Cystic lesion in the umbilical cord caused by persistence and dilatation of a segment of the omphalomesenteric duct lined by epithelium of gastrointestinal origin.
Found closer to the fetal cord insertion
More common in females (5:3)

50
Q

Varix of the umbilical vessels

A

Focal dilatations of the umbilical vessels affecting the umbilical artery and vein.
Appears as a dilated intra-abdominal, extra hepatic portion of the umbilical vein

51
Q

Omphalocele

A

Results in failure of the intestines to return to the abdomen. Hernia may consist of a single loop of bowel or contain most of the intestines.
-1 in 5000 births

52
Q

Gastroschisis

A

Right paraumbilical defect involving all layers of the abdominal wall, 2-4 cm. Never covered by membrane; directly exposed.

53
Q

Amniotic band syndrome

A

Multiple fibrous strands of amnion that develop in utero that may enable fetal parts to cause amputations malformations of the fetus

54
Q

Hypoplastic umbilical artery

A

When one artery is smaller than the other.
Discordant blood flow seen in umbilical artery Doppler.
Resistive index is higher in the smaller artery, and end-diastolic flow may be absent
Associated with placental pathology, polyhydramnios, congenital heart disease, fetal growth restriction, and stillbirth

55
Q

How is amniotic fluid developed

A

It is produced by the umbilical cord, the membranes, lungs, skin and kidneys

56
Q

When does fetal production of urine and swallowing begin

A

8-11 weeks gestation

*urine production is most significant at 18-20 weeks

57
Q

What regulates the amount of amniotic fluid

A

The kidneys; fetus swallowing

58
Q

How much does amniotic fluid increase each day

A

10 mL/day

59
Q

Signs of polyhydramnios

A

Excessive amount of fluid that causes the uterine size to be larger than expected for gestational dates.
Volume greater than 2000 mL
*Also known as hydramnios

60
Q

Maternal conditions for polyhydramnios

A

Diabetes melitus, obesity, Rhesus incompatibility, anemia, congestive cardiac failure, and syphilis

61
Q

Signs of Oligohydraminos

A

Reduction in the amount of amniotic fluid resulting in fetal crowding and decrease fetal movement

62
Q

Amniotic sheets

A

Identified as echogenic nonfloating bands that cross through the amniotic cavity. Thicker bands associated with amniotic band syndrome.
Doesn’t cause fetal malformations and most likely signify uterine synechiae

63
Q

Whats the best way a sonographer can assess amniotic fluid

A

Subjective assessment; “eye-ball”

64
Q

Do twin pregnancies have a higher or lower AFI

A

Slightly lower AFI

65
Q

Function of the amniotic fluid

A
  • Cushion to protect fetus
  • Allows embryonic and fetal movements
  • Prevents adherence of the amnion to the embryo
  • Allows symmetrical growth
  • Maintains constant temperature
  • Acts as a reservoir to fetal metabolites before their exertion by the maternal system
66
Q

When may amniotic fluid appear generous

A

20-30 weeks

67
Q

What fluid measurement is both valid and reproducible

A

AFI method

RUQ+RLQ+LUQ+LLQ=AFI

68
Q

Congenital anomalies associated with polyhydramnios

A

Central Nervous System and Gastrointestinal system

*Box 57-2 p. 1255

69
Q

What kind of prognosis does persistent oligohydramnios carry

A

Poor prognosis regardless of its cause

70
Q

Synechiae

A

Scars within the uterus

71
Q

Particles in the amniotic fluid

A
  • vernix caseosa

- Amniotic sludge-used to describe dense collection of echogenic particles within the fluid at the level of the cervix

72
Q

Normal AFI

A

10-20 cm (2 cm pocket)

  • Low: 5-10 cm
  • High: 20-24 cm
73
Q

Maximum vertical pocket

A

Assessment of amniotic fluid is done by identifying the largest pocket of amniotic fluid, should measure greater than 1 cm
Measured at right angles to uterine contour

  • Oligo: <2cm
  • Normal: 2-8 cm
  • Poly: >8cm
74
Q

Non anomalous reasons for oligohydramnios

A
  • IUGR
  • Premature rupture of membranes
  • Postdate pregnancy (42 weeks)
  • Chorionic villous sampling

LMC Ultrasound (32 decks)

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