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OB Flashcards

1
Q

What are the two signs that may aid in the detection of very early pregnancy?

A

Intradecidual and double decidual sac signs

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2
Q

What is the Intradecidual Sign?

A

Represents the gestational sac w/in the thickened decidua, seen at <5 weeks.

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3
Q

What is the Double Decidual Sac?

A

Two echogenic rings encircling the gestational sac. Most useful when seen, confirms the presence of an intrauterine pregnancy.

Absence is considered indeterminate.

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4
Q

What is a pseudogestational sac?

A

Intrauterine fluid collection surrounded by a single decidual layer- seen in the context of ectopic pregnancy.

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5
Q

What is a normal and slow HR for a CRL of <4 mm?

A

<90 is slow and >100 is normal

No such thing as too fast

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6
Q

What is normal and slow HR for a CRL of 5-9 mm?

A

<110 is slow and >120 is normal.

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7
Q

What parameters are used for gestational age between 5 and 6 weeks?

A

Gestational sac only (with or without double sac sign): 5 weeks
Gestational sac with a yolk sac, but w/o an embryo: 5.5 weeks
Gestational sac with an embryo <3 mm and heartbeat: 6 weeks

For embryos >3 mm in length, a CRL is used to assign gestational age using established reference tables.

CRL can estimate gestational age up to 12 weeks- after use multiple fetal measurements.

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8
Q

What first trimester findings are considered guarded pregnancy prognosis (f/u US recommended)?

A

MSD >8 mm with no yolk sac
MSD >16 mm with a yolk sac but no embryo
Yolk sac >6 mm portends a poor prognosis even if an embryo has a normal HR
HR <90 after 6 weeks
Any visible embryo should have a heartbeat. If not seen, very little chance of successful pregnancy.

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9
Q

What first trimester findings are considered definite pregnancy failure?

A

Known gestational age >6.5 weeks with no heartbeat.

Need prior US that established dating, or patient underwent in vitro fertilization with a known embryo transfer date.

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10
Q

What is chance of ectopic in a patient with newly positive pregnancy test and pain or bleeding before any imaging performed?

A

15%

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11
Q

Chance of ectopic pregnancy with no IUP with tubal ring or adnexal mass (no embryo or YS)?

A

Tubal ring: 95% risk of ectopic

Adnexal mass: 92% risk of ectopic

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12
Q

Chance of ectopic pregnancy with no IUP with normal adnexa?

A

5-33% risk of ectopic if patient stable, f/u US performed.

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13
Q

Situations in which 100% certainty of r/u ectopic pregnancy.

A

Extrauterine gestational sac with embryo or yolk sac

Normal IUP with normal adnexae

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14
Q

MC site for ectopic pregnancy?

A

Tubal is MC

Ampullary is MC in tubal

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15
Q

hCG trends with IUP, ectopic, and spontaneous abortions

A

IUP- rises exponentially
Ectopic- plateaus
Spontaneous abortion- falls

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16
Q

What is Gestational Trophoblastic Disease?

A

AKA hydatidiform molar pregnancy.

Invasive neoplastic overgrowth of the trophoblast into the myometrium or beyond. Trophoblast normally develops into the placenta.

Presents with emesis, markedly elevated hCG, and enlarged uterus. May also have painless vaginal bleeding.

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17
Q

What are the two types of molar pregnancy?

A

Complete- do not contain any fetal parts - loss of the egg’s DNA prior to fertilization by the sperm - diploid karyotype of 46,XX or 46 XY. May progress to metastatic choriocarcinoma.

Partial Hydatidiform Mole- Associated with some fetal development - two sperm fertilizing the same egg- has triploid karyotype of 69,XXX, 69,XXY, or 69,XYY. Less likely to progress to choriocarcinoma.

US- snowstorm appearance- visualization of fetal parts suggests a partial mole.

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18
Q

What is a Complete Molar Pregnancy?

A

Does not contain any fetal parts. Loss of egg’s DNA prior to fertilization by the sperm

Diploid karyotype of 46,XX (most commonly) or 46,XY.

Can progress to metastatic choriocarcinoma.

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19
Q

What is a Partial Molar Pregnancy?

A

Associated with some fetal development. Two sperm fertilizing the same egg.

Triploid karyotype of 69,XXX, 69,XXY, or 69,XYY.

Less likely to progress to choriocarcinoma.

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20
Q

What is Chorioadenoma detruens?

A

Complete mole that invades the myometrium.

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21
Q

What is Chorionicity vs Amnionicity?

A

Chorionicity = number of placentas

Amnionicity = number of amniotic sacs

Chorionicity should be listed first.

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22
Q

Difference between monozygotic vs dizygotic twins?

A

Monozygotic (identical) - arise from single egg fertilized with a single sperm - can have any placentation type depending on when the developing zygote splits.

Dizygotic (fraternal) - arise from two individually fertilized eggs - always diamniotic/dichorionic - can have two different sexes.

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23
Q

Risk of mono/di twins?

A

Increased risk of complications related to shared placenta, including twin-twin transfusion, acardiac twin syndrome, and twin embolization.

Di/di twins have increased risk of premature delivery and low birth weight compared to singleton gestations..

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24
Q

Risks for mono/mono twins?

A

Same complications as Mono/di twins (twin-twin transfusion, acardiac twin syndrome, and twin embolization) plus at risk for cord entanglement and being conjoined.

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25
Q

If two separate gestational sacs are identified =

A

Placentation is di/di - zygosity is indeterminate.

Dizygotic twins are always di/di, early splitting of a single fertilized egg can also lead to di/di monozygotic twins.

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26
Q

If a single gestational sac is identified with two yolk sacs =

A

Single gestational sac with two yolk sacs- placentation is mono/di and twins are monozygotic

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27
Q

Breakdown of how monozygotic twins split?

A

33%: 0-4 days- still in fallopian tube: dichorionic, diamniotic

66%: 4-8 days- after implantation in uterus and after formation of placenta, but before the amnion has developed: monochorionic, diamniotic

1%: Split >8 days- after development of chorion and amnion: monochorionic, monoamniotic

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28
Q

What causes conjoined twins?

A

Late (>13 days) incomplete division of the embryo.

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29
Q

Criteria to diagnose twin-twin transfusion syndrome?

A

Disproportionate fetal sizes, with at least 25% discrepancy.

Disproportionate amniotic fluid, with the small twin (donor) having oligohydramnios and the large twin (recipient) having polyhydramnios.

Single shared placenta (monochorionic).

Early stages donor twin’s bladder is visible and the direction of umbilical artery Doppler flow is normal - later stages are marked by fetal hydrops or death.

Stuck twin- severe oligohydramnios in donor twin- amnion is wrapped around the twin like shrink wrap.

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30
Q

What are Acardiac Twins?

A

Also called twin reversed arterial perfusion (TRAP) sequence - severe variant of twin-twin perfusion syndrome. Complication of monochorionic twins.

The donor fetus supplies circulation to itself and an acardiac twin, enabled by placental fistulous connections. Acardiac twin has rudimentary or no development of structures above the thorax.

Doppler shows reversed flow in the acardiac twin.

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31
Q

Normal function of the umbilial arteries and veins?

A

Umbilical Arteries (2)- carry deoxygenated blood OUT of the fetus, pumped by the fetal heart

Umbilical Vein (1)- carries oxygenated blood INTO the fetus, from the placenta.

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32
Q

What is twin embolization syndrome?

A

Monochorioic twin dies in utero- surviving twin is at risk for CNS, GI, or renal infarcts.

Better prognosis for dichorionic twins.

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33
Q

By 8 weeks what cranial structures should be seen?

A

Forebrain (prosencephalon) and hindbrain (rhombencephalon).

Both are hypoechoic, although the rhombencephalon is much more prominent.

Absence may be earliest finding of anencephaly.

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34
Q

When is normal physiologic ventral midgut herniation complete?

A

12-13 weeks.

Rotates 270 degrees around the SMA.

Omphalocele or Gastroschisis is generally not diagnosed before 13 weeks.

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35
Q

Settings needed to measure nuchal translucency

A 
High-contrast nuchal setting
Fetal head should fill most of the screen
Nasal bone should be visible
Neck should be in neutral position
Measure inner-inner at the widest point
Amnion should be visible

At 11 weeks, upper limit of normal is 2.2 mm
At 14 weeks (CRL 79 mm), the upper limit of normal is 2.8 mm.
Combined with maternal serum testing to calculate overall risk of Trisomy 21 - seen in 2/3 of cases.

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36
Q

How is biparietal diameter measured?

A

From outer edge of skull closest to transducer to the inner edge of skull farthest from transducer.

At the level of the thalami and cavum septum pellucidum. Skull should be completely visualized all the way around.

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37
Q

How is occipital frontal diameter measured?

A

From the middle of the frontal skull to the middle of the occipital skull.

Same plane as BPD - At the level of the thalami and cavum septum pellucidum. Skull should be completely visualized all the way around.

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38
Q

Where is abdominal diameter measured?

A

Outer skin-to-skin in AP and transverse at the level of the intrahepatic umbilical vein, portal vein, and fetal stomach.

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39
Q

What is Amniotic Fluid Index (AFI)?

A

Quantify amniotic fluid between 16 and 42 weeks. Varies with gestational age. Should always be subjectively assessed.

Largest vertical pocket is measured (in cm) in each of the four quadrants and summed.

Oligohydramnios: AFI <6.3 cm is <2.5th percentile. Peaks at 24 weeks: 9cm = 2.5th percentile

Polyhydramnios: AFI >19.2 cm is >97.5th percentile. Peaks at 36 weeks: 27.9 cm = 97.5th perentile.

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40
Q

When is nucal fold thickness checked?

A

2nd trimester - most sensitive and specific US finding to suggest Down syndrome.

Nuchal lucency is measured earlier in pregnancy

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41
Q

How is Nuchal Fold Thickness measured?

A

2nd trimester - 16-20 weeks - later than nuchal lucency - most sensitive and specific US finding for Down syndrome

Measured in the axial plane at the level of the posterior fossa.

<5 mm is normal
5-5.9 mm is borderline
>6 mm is a major marker for Trisomy 21

Very thick nuchal fold may represent a cystic hygroma- associated with Turner Syndrome (45,X).

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42
Q

Most sensitive and specific US finding for Down Syndrome?

A

Nuchal Fold Thickness

Measured in the axial plane at the level of the posterior fossa.

<5 mm is normal
5-5.9 mm is borderline
>6 mm is a major marker for Trisomy 21

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43
Q

What is considered cervical shortening?

A

Cervical length <3 cm is abnormal. Also seen change in shape.

Trust Your Vaginal Ultrasound - sequence of cervical funneling.
T-shaped is normal
As funneling progresses, resembles Y, V, and U shapes.

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44
Q

What is treatment for cervical shortening?

A

<24 weeks- cervical cerclage

>24 weeks- conservative/bedrest- concern for membrane rupture with any procedure.

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45
Q

What is the placenta made of?

A

Fetal chorion and maternal endometrium.

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46
Q

What is a single umbilical artery associated with?

A

Fetal anomalies (MC cardiovascular) in up to 50% of fetuses.

Increased incidence of single UA in trisomies 13 and 18.

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47
Q

What happens to the placenta in fetal hydrops?

A

Thickened

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48
Q

What is Vasa Previa?

A

Traversing of placental vessels across the internal cervical os which can be caused by velamentous insertion or a placental succenturiate lobe.

Velamentous Insertion- Insertion of the umbilical cord outside the margin of the placenta

Succenturiate Lobe- Island of placental tissue separate from the main placenta, connected to the main placental by blood vessels.

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49
Q

What is Velamentous Insertion of the umbilical cord?

A

Insertion of the umbilical cord outside the margin of the placenta

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50
Q

What is a Succenturiate Lobe of the Placenta?

A

Island of placental tissue separate from the main placenta, connected to the main placental by blood vessels.

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51
Q

How far should the edge of the placenta be from the internal cervical os?

A

> 3 cm

True previa = placenta covers the internal cervical os.

Need empty bladder and realtime scanning should be done to confirm the lack of active contractions.

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52
Q

Risks for placental abruption?

A

Maternal HTN, drug abuse, trauma, or rapid decompression of a distended uterus (large volume amniocentesis).

Negative US cannot exclude abruption.

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53
Q

Anterior placenta + prior C-section

A

Placental Accreta possible

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54
Q

Findings of placenta accreta

A

Loss of the normal retroplacental clear space, abnormalities at the bladder/placental interface, and prominent vascular lacunar spaces.

Presence of a moth-eaten placenta with vascular lacunar spaces near the bladder is highly specific for accreta.

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55
Q

Difference between placenta accreta, increta, and percreta?

A

Accreta - Attaches deeply into the myometrium, but does not invade - US shows thinning or absence of the normal hypoechoic subplacental zone.

Increta - Invades into the myometrium

Percreta - Penetrates through the myometrium and into or through the serosa.

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56
Q

What is Fetal Hydrops?

A

Fluid-overload state.

Two:
Ascites, pleural or pericardial effusion, skin thickening, polyhydramnios, and placental enlargement.

Immune vs Non-immune. Prognosis worse for non-immune

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57
Q

What is Immune Fetal Hydrops?

A

Immune-mediated hydrops is fetal hemolytic anemia caused by prior maternal exposure to fetal antigens - by far MC is Rh antigen.

Prognosis is good if treated with intrauterine or peripartum fetal blood transfusions.

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58
Q

What is Non-immune Hydrops?

A

Diverse array of causes which lead to a common pathway of extracellular fluid overload. Prognosis is poor, as primary cause is not often effectively treatable.

Primary cardiac - structural and arrhythmias.
Extracardiac shunt- Vein of Galen malformation, hepatic hemangioendothelioma, and twin-twin transfusion syndrome - lead to high output cardiac failure.
Infectious- parvovirus B19 and TORCH infections
Decreased oncotic pressure, hepatitis and fetal nephrotic syndrome.
Increased capillary permeability, can be due to anoxic injury
Venous obstruction, seen in Turner (45,X) syndrome.

59
Q

Causes of Non-immune Hydrops?

A

Primary cardiac - structural and arrhythmias.
Extracardiac shunt- Vein of Galen malformation, hepatic hemangioendothelioma, and twin-twin transfusion syndrome - lead to high output cardiac failure.
Infectious- parvovirus B19 and TORCH infections
Decreased oncotic pressure, hepatitis and fetal nephrotic syndrome.
Increased capillary permeability, can be due to anoxic injury
Venous obstruction, seen in Turner (45,X) syndrome.

All lead to a common pathway of extracellular fluid overload.

60
Q

What causes fetal ascites?

A

When seen with other abnormalities, is a criteria for diagnosis of hydrops.

Isolated- urinary obstruction and resultant calyceal or bladder rupture or meconium peritonitis.

61
Q

What causes fetal pleural effusions?

A

Criterion for diagnosis of hydrops.

Isolation- MC caused by congenital chylothorax - thoracic duct or lymphatic malformation.

Fetal pleural effusions can also be seen in Turner or Down syndromes.

62
Q

GU abnormalities that may lead to oligohydramnios?

A

Renal agenesis- fatal if bilateral
Congenital bladder outlet obstruction, including posterior urethral valves
Bilateral ureteropelvic junction obstructions
Renal dysplasias, including ARPKD

63
Q

Causes of polyhydramnios?

A

> 1/2 are idiopathic, with a normal fetus. Remainder associated with chromosomal abnormalities, DM, or structural defects (primarily of GI tract):

Primary upper GI obstruction or atresia, such as laryngeal, esophageal, or duodenal atresia.
Secondary obstruction, due to diaphragmatic hernia, gastroischisis, or omphalocele.
Severe CNS anomalies - disorders in swallowing
Monochorionic twin syndromes, such as twin-twin transfusion syndrome
Placental abnormalities, such as chorioangioma - benign placental hemangioma that may cause polyhydramnios when highly vascular.

64
Q

Ventriculomegaly vs Hydrocephalus?

A

Ventriculomegaly = enlargement of the cerebral ventricles

Hydrocephalus = implies due to obstruction.

Throughout gestation, the lateral ventricles should each measure less than 10 mm when measured at the atrium.

65
Q

Causes of ventriculomegaly?

A

Sign that something else is wrong, diverse array of etiologies:

Primary CNS structural (aqueductal stenosis, Dandy Walker, Chiari II, holoprosencephaly, agenesis of the CC)

Genetic- trisomies 13 and 18

Destructive - infection, hemorrhage, or infarct

Idiopathic

66
Q

What is Anencephaly?

A

Lethal anomaly with complete lack of development of fetal cerebral cortex and calvarium above the orbits.

AFP is elevated

Angiomatous Stroma- residual neural-type tissue that may be tethered above the head and may be confused with an encephalocele

DDx is amniotic band syndrome, which is almost always asymmetric.

67
Q

DDx of a mass posterior to the occipital skull?

A

Cephalocele

Cystic hygroma- congenital lymphatic malformation and the most common fetal neck mass

68
Q

MC fetal neck mass?

A

Cystic hygroma- congenital lymphatic malformation

69
Q

What is Dandy Walker Malformation?

A

Diverse spectrum of diseases characterized by hypogenesis of the cerebellar vermis and resultant fourth ventricle dilation.

Associated with agenesis of the corpus callosum.

70
Q

What is the Banana sign of Chiari II?

A

Flattened cerebellar hemispheres in the small posterior fossa.

Very specific for Chiari II- if seen, lumbar myelomeningocele is presumed to be present.

71
Q

What is the Lemon sign of Chiari II?

A

Flattening of the frontal bones, causing the calvarium to have the morphology of a lemon when seen axially - not specific for Chiari II.

72
Q

What is Holoprosencephaly?

A

Failure of midline cleavage of the primitive prosencephalon in early embryologic development.

Most severe = alobar holoprosencephaly - fused thalami and a single monoventricle that may communicate with a large dorsal cyst. Brain tissue surrounds the monoventricle, forming a characteristic boomerange shape.

Associated with trisomy 13, facial hypoplasias, and midline facial anomalies including clefts.

73
Q

Secondary Signs of Agenesis of the Corpus Callosum?

A

Absence of the cavum septum pellucidum

Abnormal teardrop morphology with dilated occipital horns - colpocephaly, often seen together with ventriculomegaly.

Widely separated ventricular frontal horns and parallel configuration of the lateral ventricles.

Medial borders of the lateral ventricles may be concave due to protrusion of Probst bundles (axons that normally constitue the corpus callosum) and the cingulate gyrus.

Midline interhemispheric cyst - representing superior herniation of the third ventricle.

74
Q

Absence of the cavum septum pellucidum in the presence of a normal corpus callosum?

A

May represent septo-optic dysplasia - fetal MRI should be recommended.

75
Q

What is Hydranencephaly?

A

Complete cortical destruction due to infarct or infection. Brain parenchyma is obliterated and replaced by fluid.

MC is MCA occlusion.
Cortical mantle is absent, in contrast to severe hydrocephalus

76
Q

What is Congenital Pulmonary Airway Malformation (CPAM)?

A

Hamartomatous proliferation of small airways that communicates with the bronchial tree.

Blood supply is from the pulmonary circulation.

Classified by the size of the cysts. Prognosis is dependent on the size of the entire lesion rather than size of the individual cysts.

Not associated with other anomalies (unlike congenital diaphragmatic hernia).

Can appear to regress on US, but will be there on CT or MRI.

77
Q

What is congenital diaphragmatic hernia associated with?

A

Most are isolated anomalies, but can be associated with congenital heart disease.

78
Q

What is sequestration?

A

Aberrant lung tissue with a systemic blood supply, usually from the aorta.

MC location is the LLL - echogenic mass at the left lung base. May be subdiaphragmatic and simulate an adrenal mass.

Systemic blood supply should be confirmed with color Doppler - w/o Doppler findings, sequestration may be difficult to differentiate from CPAM

79
Q

Findings of esophageal atresia on US?

A

Polyhydramnios and an absent stomach bubble.

Usually associated with a TE fistula.

80
Q

What is Duodenal atresia associated with?

A

Downs

81
Q

DDx of double bubble?

A

Duodenal atresia
Duodenal web
Stenosis
Annular Pancreas

82
Q

What is VACTERL?

A 
Vertebral
Anorectal
Cardiac
TE
Renal
Limb anomalies
83
Q

Structural causes of distal fetal bowel obstruction

A

Structural or functional

Structural- jejunal atresia, ileal atresia, and anorectal malformation.

Functional- Hirschsprung or meconium ileus (cystic fibrosis)

84
Q

What is a meconium pseudocyst?

A

Cystic abdominal structure, often with peripheral calcification, representing a walled-off bowel perforation.

Sequela of meconium peritonitis.

85
Q

Causes of hyperechoic small bowel

A

Nonspecific - more echogenic than bone.

Downs, TORCH, CF, and swallowing of intra-amniotic blood. May be associated with intrauterine growth restriction.

86
Q

What are omphaloceles associated with?

A

Other anomalies 50-75% of cases

Cardiac anomalies
Trisomies
Beckwith-Wiedemann Syndrome

Gastroschisis is usually an isolated anomaly.

87
Q

What is the Pentalogy of Cantrell?

A 
Ectopica Cordis (extra-thoracic heart)
Omphalocele
Diaphragmatic defect
Pericardial defect
Disruption of the sternum
88
Q

Hydronephrosis, hydroureter, and normal bladder

A

Distal ureteral obstruction or reflux.

Ectopic insertion of the ureter - often associated with the upper pole moiety of a duplicated collecting system - inferior and medial to the lower pole ureter

Ureterocele, causes a functional obstruction

Severe vesicoureteral reflux - not a physical obstruction, but may cause hydro and the bladder remains normal.

89
Q

Hydronephrosis, hydroureter, and dilated bladder

A

Bladder outlet obstruction

Posterior urethral valves - MC
Urethral atresia

90
Q

What can chronic hydro lead to?

A

Cystic renal dysplasia - a sign of irreversible renal damage.

Multicystic Dysplastic Kidney - multiple non-communicating cysts interspersed with dysplastic renal parenchyma - not connected to the collecting system.

91
Q

What is Thanatophoric Dysplasia?

A

Lethal skeletal dysplasia with characteristic telephone receiver femurs, severe limb shortening and bowing, and rib shortening.

Platyspondyly is characteristic- flattening of ossified portions of the vertebral bodies.

Cloverleaf skull is caused by protrusion of the frontal and temporal lobes.

Bone mineralization is normal - unlike OI.

92
Q

Findings associated with Trisomy 13

A 
Holoprosencephaly and midline facial anomalies
Encephalocele
Congenital heart disease
Omphalocele
Horseshoe kidney
Polycystic kidneys
Polydactyly
93
Q

Findings associated with Trisomy 18

A 
Strawberry sign- inward bowing of the frontal bones creates a strawberry shape to the calvarium, with the tip of the strawberry projected anteriorly
Choroid plexus cyst
Facial cleft
Micrognathia
Cardiac anomalies
Omphalocele
Congenital diaphragmatic hernia
Horseshoe kidney
Hydronephrosis
Clenched hand that never opens, with overlapping fingers
Rocker bottom feet
94
Q

Findings of Downs Trisomy 21

A

Increase in nuchal fold (>6 mm)- measured between weeks 15 and 21- most sensitive and specific
Nuchal translucency
Absent ossification of nasal bone
Cystic hygroma- more common in Turner syndrome
Congenital heart disease: VSD and encocardial cushion defect
Echogenic bowel
Duodenal atresia
Echogenic cardiac focus
Shortened femur and humerus
Hypoplasia of the middle phalanx of the little finger
Sandal gap toes

95
Q

Findings of Beckwith-Wiedemann Syndrome

A

Syndrome of overgrowth that carries an increased risk of childhood cancers

Increased risk of Wilms tumor (most commonly), hepatoblastoma, and other childhood tumors
Hemihypertrophy, organomegaly
Macroglossia
Omphalocele
Perinatal hypoglycemia
96
Q

Findings of Meckel-Gruber Syndrome

A

AR multi-organ syndrome

Encephalocele
Renal dysplasia causing multiple tiny renal cysts, which appear as echogenic kidneys, analogous to ARPKD
Polydactyly

97
Q

Grading of Germinal Matrix Hemorrhage

A

Germinal matrix is site of neuronal percuror cells located in the caudothalamic groove

I: hemorrhage confined to the germinal matrix
II: extends into the ventricles w/o ventriculomegaly
III: extends into the ventricles with ventriculomegaly
IV: extends out of the ventricles into the parenchyma

98
Q

OB Terminology

A

Menstrual Age: Embryological Age + 14 days
Embryo: 0-10 weeks (menstrual age)
Fetus: >10 weeks (menstrual age)
Threatened Abortion - Bleeding with closed cervix
Inevitable Abortion: Cervical dilation and/or placental and/or fetal tissue hanging out
Incomplete Abortion: Residual products in the uterus
Complete Abortion: All products out
Missed abortion: Fetus is dead, but still in the uterus

99
Q

What is the Double Deciual Sac Sign?

A

Positive sign of early pregnancy. Produced by visualizing the layers of decidua.

Small amount of fluid between the Decidua Capsularis (inner) and Decidua Vera (outer).

100
Q

Where is the yolk sac located? What is normal size?

A

In the chorionic cavity.

Shouldn’t be >6 mm or <3 mm.

101
Q

What happens to the chorion and amnion?

A

Membranes of the amniotic sac and chorionic space typically remain separated by a thin layer of fluid, until about 14-16 weeks at which point fusion is normal.

If amnion gets disrupted before 10 weeks, the fetus might cross into the chorionic cavity and get tangled up in the fibrous bands - amniotic band syndrome.

102
Q

What is the Double Bleb Sign?

A

Earliest visualization of the embryo. Two fluid filled sacs (yolk and amniotic) with the flat embryo in the middle. Placenta will be inferior.

103
Q

Diagnostic of Pregnancy Failure vs Suspicious for pregnancy failure

A

Diagnostic:
CR length of >7 and no heartbeat
Mean sac diameter of >25 mm and no embryo
No embryo with heart beat >11 days after a scan that showed a gestational sac with a yolk sac
No embryo with heartbeat >2 wk after a scan that showed a gestational sac without a yolk sac.

Suspicious:
No embryo >6 weeks after last menstrual period
Mean sac diameter of 16-24 mm and no embryo
No embryo w heartbeat 13 days after a scan that showed a GS w/o a yolk sac
No embryo with a heartbeat 10 days after a scan that showed a gestational sac with a yolk sac.

104
Q

MC place for ectopic pregnancy?

A

Isthmus of fallopian tube

105
Q

Big 3 to remember with ectopics (positive bHCG)

A

Liver pregnancy/yolk sac outside uterus = ectopic

Nothing in the uterus + anything on the adnexa (other than corpus luteum) = 75-85% PPV for ectopic. A moderate volume of free fluid increases this to 97% PPV.

Nothing in uterus + moderate free fluid = 70% PPV. More risk if the fluid is echogenic.

106
Q

What is the Tubal Ring Sign?

A

Echogenic ring which surrounds an unruptured ectopic pregnancy. Excellent sign of ectopic pregnancy - 95% specific.

107
Q

What are the fetal measurements for growth?

A

Biparietal Diameter “BPD” - At level of thalamus from the outermost edge of the near skull to the inner table of the far skull - Affected by the shape of the fetal skull (false large from brachycephaly, false small from dolichocephaly)

Head Circumference - Recorded at the same slice as BPD - Does NOT include the skin - Affected less by head shape.

Abdominal Circumference - Recorded at the level of the junction of the umbilical vein and L portal vein - Does NOT include the SQ soft tissues.

Femur Length - Longest dimension of the femoral shaft - Femoral epiphysis is NOT included.

108
Q

What is Gestational Age?

A

US estimates of GA are the most accurate in an early pregnancy (and become less precise in later portions). Age at first trimester is made from CRL. 2nd and 3rd are done using BPD, HC, AC, and FL - and referred to as “composite GA.”

109
Q

Findings suggestive of IUGR?

A

Estimated fetal weights below 10th percentile
Femur length/abdominal circumference ratio (F?AC) > 23.5
UA systolic/diastolic ration >4.0

If kid is measuring small, suggesting IUGR and he has oligohydramnios (AFI <5) or polyhydramnios he/she is probably lost.

110
Q

What is Asymmetrical vs Symmetric IUGR?

A

Asymmetric - restriction of weight followed by length. MC of the two types. Head normal in size with body being small - “head sparing.” Mainly in 3rd trimester. High BP, Severe Malnutrition, Ehler-Danlos.
Normal growth for the first two trimesters with a normal head/small body in the third trimester - mom having chronic high BP/pre-eclampsia.

Symmetric - Global growth restriction that does NOT spare the head. Seen throughout the pregnancy (including first trimester). Head and body are both small. Much worse prognosis as brain doesn’t develop normally.
TORCH infection, fetal alcohol syndrome/drug abuse, chromosomal abnormalities and anemia.

111
Q

What is the Biophysical Profile?

A

Look for acute and chronic hypoxia. Points are assigned (2 for normal, 0 for abnormal). Score of 8-10 is considered normal. To say abnormal need to watch for 30 min.

Amniotic fluid - At least one pocket that measures 2 cm or more in a vertical plane
Fetal Movement - 3 discrete movements
Fetal Tone - 1 episode of fetal extension from flexion
Fetal Breathing - 1 episode of “breathing motion” lasting 30 seconds
Non-stress Test - 2 or more fetal HR accelerations of at least 15 bpm and or 30 seconds or longer.

112
Q

What is UA Systolic/Diastolic Ratio?

A

Resistance in UA should progressively decrease with GA. 2-3 at 32 weeks. ratio should not be more than 3 at 34 weeks.

Elevated S/D ratio means there is high resistance - seen in pre-eclapsia and IUGR. Worse than an elevated ratio, is absent or reversed diastolic flow - very poor prognosis.

113
Q

What is Erb’s Palsy?

A

Injury to upper trunk of the brachial plexus (C5-C6), MC seen in shoulder dystocia (kids with macrosomia are at risk for).

Aplastic or hypoplastic humeral head/glenoid in a kid - Erb’s palsy.

114
Q

What is the Amniotic Fluid Index?

A

Measuring the vertical height of the deepest fluid pocket in each quadrant of the uterus then summing the 4 measurements.

Normal is 5-20. Oligohydramnios is defined as AFI <5 cm. Polyhydramnios is defined as AFI > 20 cm or a single fluid pocket >8 cm.

115
Q

What is a Cystic Rhombencephalon?

A

Normal rhombencephalon is present as a cystic structure in the posterior fossa 6-8 weeks.

Don’t call a Dandy-Walker malformation.

116
Q

What does normal placental aging look like?

A

Hypoechoic areas, septations, and randomly distributed calcifications.

117
Q

What causes placenta that is too thick vs too thin?

A

Too thin (<1 cm): Placental insufficiency, maternal HTN, maternal DM, Trisomy 13, Trisomy 18, Toxemia of pregnancy.

Too thick (>4 cm): Fetal hydrops, maternal DM, Severe maternal anemia, congenital fetal cancer, congenital infection, placental abruption.

118
Q

What are the variant shapes of placenta?

A

Bilobed: Two near equal sized lobes. Increased risk of type 2 vasa previa, post partum hemorrhage from retained placental tissue, and velamentous insertion of the cord.

Succenturiate Lobe: One or more small accessory lobes. Increased risk of type 2 vasa previa, post partum hemorrhage from retained placental tissue.

Circumvallate Placenta: Rolled placental edges with smaller chorionic plate. High risk for placental abruption and IUGR.

119
Q

What is Placenta Previa?

A

Low implantation of the placenta that covers part or all of the internal cervical os.

Painless vaginal bleeding in the third trimester.

Need to have an empty bladder when you look for this.

120
Q

Difference between placental abruption and myometrial contraction/fibroid?

A

Placental abruption will disrupt the retroplacental complex of blood vessels.

Myometrial contractions/fibroids will displace the retroplacental complex.

121
Q

Risk factors for Placenta Creta?

A

Prior C-section, placenta previa, and advanced maternal age.

Moth-eaten or Swiss cheese appearance of the placenta with vascular channels extending from the placenta into the myometrium (with turbulent flow on Doppler).
Thinning of the myometrium (<1 mm) is another sign.

Accreta- attached
Increta- partially invades
Percreta- penetrates

122
Q

What is a Placenta Chorioangioma?

A

Hamartoma of the placenta. MC benign tumor of the placenta.

Well circumscribed hypoechoic masses near the cord insertion. Flow w/in the mass pulsating at the fetal HR is diagnostic (they are perfused by the fetal circulation).

Mean nothing, but hwen large (>4 cm) and multiple (“choriangiomatosis”) they can sequester platelets, and cause a high output failure (hydrops).

**Vs Placental Hematoma - Hematoma does NOT have pulsating Doppler flow.

123
Q

What is a normal cord vs 2 vessel cord?

A

Normal - 3 vessels (2 arteries, 1 vein)

Two vessel: Normal variant. Usually the left artery is the one missing. Tends to occur more in twin pregnancies and maternal DM. Increased association with chromosome anomalies and various fetal malformations.

124
Q

What is Velamentous vs Marginal Cord insertion?

A

Velamentous: When the cord inserts into the fetal membranes outside the placental margin and then has to travel back through the membranes to the placenta (between the amnion and chorion). More common with twins and increases the risk of IUGR and growth discordance among twins.

Marginal: Almost a velamentous insertion (cord is w/in 2 cm of the placental margin). Also seen more in twin pregnancies.

125
Q

What is Vasa Previa?

A

Fetal vessels that cross (or almost cross) the internal cervical os. MC in twin pregnancies, and variant placental morphologies.

Type 1: Fetal vessels connect to a velamentous cord insertion w/in the main body of the placenta.

Type 2: Fetal vessels connect to a bilobed placenta or succenturiate lobe.

126
Q

What is an umbilical cord cyst?

A

Can be false or true cysts- true are less common.

Omphalomesenteric duct cyst is usually peripheral, and the allantoic cyst is usually central.
If the cyst persist into the 2nd or 3rd trimester then they might be associated with trisomy 18 or 13. Look closely for other problems.

127
Q

US findings concerning for Downs

A

Congenital Heart Disease: MC AV canal and VSD
Duodenal Atresia: MC abdominal pathology associated with Downs
Short Femur Length: Not specific
Echogenic Bowel: Not specific - can be seen with obstruction, CF, ischemia, and lots of other stuff.
Choroid Plexus cyst: Not specific
Nuchal Translucency: >3 mm in first trimester
Nuchal Fold Thickness: >6 mm in 2nd trimester, non specific and can be seen with Turners.
Echogenic Focus in Cardiac Ventricle

128
Q

What is Nuchal Lucency and when should it be measured?

A

Between 0-12 weeks.

Should be <3 mm.

129
Q

What is Fetal Hydrops?

A

Immune or non-immune causes

Rh sensitization from prior pregnancy. TORCH, Turners, Twin related stuff, and alpha thalassemia.

US (2 of following): pleural effusion, pericardial effusion, and SQ edema.
Can have a thickened placenta

130
Q

What is the Lemon Sign?

A

Appearance of an indented frontal bone, classically seen as a sign of Chiari II - although seen a lot in spina bifida.
Typically see before 24 weeks (often disappears after 24 weeks).

131
Q

What is the Banana Sign?

A

Way the cerebellum wraps around the brainstem as the result of spinal cord tethering (and downward migration of the posterior fossa) looks like a banana.

Just like lemon sign - seen with Chiari II and Spinal bifida.

Anterior curving of the cerebellar hemispheres with simultaneous obliteration of the cisterna magna.
Neural tube defect = CSF leak = hypotension in the SA space with prolapse of the cerebellum into the foramen magnum

132
Q

What is a Choroid Plexus Cyst associated with?

A

Trisomy 18, Trisomy 21, Turners, and Klinefelters

133
Q

What is cystic hygroma associated with?

A

Downs and Turners

134
Q

What is Anencephaly?

A

MC neural tube defect. Total absence of the cranial vault and brain above the level of the orbits. Not compatible with life.

135
Q

DDx of echogenic bowel?

A

CF, Downs and other trisomies, viral infections, and bowel atresia.

Bowel is normally isoechoic to liver. If equal to the iliac crest bone then it’s too bright.

136
Q

Measurement of incompetent cervix?

A

> 2.5 cm in length.

137
Q

What are the things that grow during pregnancy?

A

Babies
Splenic artery aneurysms
Renal AMLs
Fibroids - 2/2 elevated estrogen - stretching can cause arterial infarcts and cystic degeneration.

138
Q

What is HELLP Syndrome?

A

Hemolysis, elevated liver enzymes, low platelets.

Most severe form of pre-eclampsia and favors young primigravid women in their 3rd trimester.

20-40% end up with DIC.

Subcapsular hepatic hematoma in pregnancy (or recently pregnant women).

139
Q

What is Peripartum Cardiomyopathy?

A

Dilated cardiomyopathy seen in the last month of pregnancy to 5 months post partum.

Cardiac MRI: global depressed function and non-vascular territory subepicardial late Gd enhancement - corresponding to cellular lymphocyte infiltration

140
Q

How to tell monochorionic vs dichorionic?

A

Membrane thickness:
Thick = “easy to see” 1-2 mm - 4 layers
Thin = “hard to see” - 2 layers

Twin-peak sign: Beak-like tongue between two membranes of a dichorionic diamniotic fetuses. Excludes monochorionic pregnancy.

T-sign: Absence of the twin peak sign. Don’t see chorion between the membrane layers. T sign = Monochorionic pregnancy.

141
Q

How do you measure twin growth?

A

Can use normal growth charts in the 1st and 2nd trimesters - but not 3rd.

Femur length tends to work best for twin age in the later pregnancy.
More than 15% difference in fetal weight or abdominal circumference between twins is considered significant.

142
Q

Which twin does better with twin-twin transfusion?

A

The skinny one.

Fat one usually gets hydrops and dies.

143
Q

What is Fetal papyraceous?

A

Pressed flat dead fetus in one dead twin.

Body (5 decks)

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