Obstetric Ultrasound: Pregnancy, Ectopic, and Fetal Anomalies

In a normal early pregnancy, how often should hCG levels double?

Every 48 hours

What two conditions are raised as concerns with sub-doubling hCG levels?

Ectopic pregnancy or failing pregnancy

What does a faster than expected rise in hCG suggest?

Multiple gestation or molar pregnancy

By what week should a gestational sac be visible?

4.5-5 weeks

By what week should a yolk sac be visible?

5-5.5 weeks

By what week should cardiac activity be detected?

5.5-6 weeks

Between which two structures does SCH form?

Chorion and uterine wall

What symptom is most associated with SCH?

Vaginal bleeding

How does SCH appear on ultrasound?

Crescent/irregular hypoechoic or anechoic area adjacent to GS

What does a large SCH (>40% GS size) increase the risk of?

Miscarriage

What is the classic symptom triad of ectopic pregnancy?

Vaginal bleeding + pelvic pain + adnexal mass

What is the most common location for ectopic pregnancy?

Ampulla of fallopian tube

What sign indicates a hypervascular ring around an ectopic?

Ring of fire

What must be ruled out when observing the ring of fire?

Corpus luteum cyst

What is a pseudogestational sac?

Fluid in endometrium mimicking GS in ectopic

Why is cornual ectopic pregnancy dangerous?

Risk of massive hemorrhage from uterine vessels

What does heterotopic pregnancy mean?

Simultaneous IUP and ectopic

What is the former name for anembryonic pregnancy?

Blighted ovum

What size of GS without yolk sac is considered abnormal?

> 25 mm

What is abnormal when a yolk sac is present but no embryo in GS > ___ mm?

20 mm

What does the 'R' in the DRIPPC mnemonic for oligohydramnios causes stand for?

Renal abnormalities

What lung condition can severe oligohydramnios lead to?

Pulmonary hypoplasia

Does a complete mole have a fetus present?

No

Does a partial mole have a fetus present?

Yes, abnormal

What is the nickname for GTD US appearance?

Snowstorm

What is the lab hallmark of GTD?

Very high hCG

What ovarian finding is often seen with GTD?

Theca lutein cysts

What is the cervix status in a threatened abortion?

Closed

What is the cervix status in an inevitable abortion?

Open

What is the definition of a missed abortion?

Fetal demise retained without symptoms

What CRL measurement without cardiac activity indicates demise?

≥ 7 mm

What is the nickname appearance of iniencephaly?

Stargazer sign

What structures are involved in iniencephaly defects?

Occiput and cervical spine

What measurement indicates ventriculomegaly?

> 10 mm

What condition can severe ventriculomegaly lead to?

Hydrocephalus

What does the dangling choroid sign indicate?

Severe ventriculomegaly

What is the hallmark of anencephaly?

Absent skull + absent cerebral hemispheres

What is the hallmark of acrania?

No skull, brain tissue present

What facial sign is associated with anencephaly?

Frog-eye sign

What type of cephalocele contains CSF only?

Meningocele

What type of cephalocele contains brain tissue?

Encephalocele

What is the most severe type of holoprosencephaly?

Alobar

What is the classic facial abnormality for holoprosencephaly?

Cyclopia

What chromosome is associated with holoprosencephaly?

Trisomy 13

What structure is absent/hypoplastic in Dandy Walker?

Cerebellar vermis

What is the posterior fossa finding in Dandy Walker?

Large cystic 4th ventricle

What skull sign is associated with Arnold Chiari II?

Lemon sign

What cerebellum sign is associated with Arnold Chiari II?

Banana sign

What spinal defect is associated with Arnold Chiari II?

Myelomeningocele

What replaces the brain in hydranencephaly?

CSF

Is the cerebellum present in hydranencephaly?

Yes

How many standard deviations below normal is microcephaly?

> 3 SD

By what gestational week does the neural tube close?

Week 4

What lab finding is common to all open neural tube defects?

Elevated AFP

What does spina bifida occulta mean?

Vertebral defect without protrusion

What two types are included in spina bifida cystica?

Meningocele & myelomeningocele

What does meningocele contain?

Meninges + CSF

What does myelomeningocele contain?

Meninges + spinal cord

What does myeloschisis mean?

Open neural plate, no sac

At what level are spinal neural tube defects most common?

Lumbosacral

What process results in hydranencephaly?

Vascular destruction of brain tissue

What process results in holoprosencephaly?

Failure of forebrain division

What is the key difference between hydranencephaly and hydrocephalus?

Hydranencephaly = no cortex; Hydrocephalus = cortex compressed

What does communicating hydrocephalus mean?

No obstruction; absorption problem

What does non-communicating hydrocephalus mean?

CSF flow obstruction

What is the most common site of obstruction in hydrocephalus?

Aqueduct of Sylvius

What does craniosynostosis mean?

Premature fusion of sutures

Brachycephaly results from fusion of which suture?

Coronal

Dolichocephaly results from fusion of which suture?

Sagittal

How is scaphocephaly described?

Long, boat-shaped head

Cloverleaf skull is associated with what condition?

Severe craniosynostosis

What does hypotelorism mean?

Eyes too close

What does hypertelorism mean?

Eyes too far apart

In which anomaly is a proboscis seen?

Holoprosencephaly

Why is the posterior fossa enlarged in Dandy Walker complex?

4th ventricle cystic dilation

What is the difference between absent and hypoplastic vermis?

Absence = classic DW; Hypoplastic = variant

Where does the cerebellum herniate in Arnold Chiari II?

Foramen magnum

Why does the lemon sign occur?

Intracranial pressure + skull molding

Zika infection is associated with what condition?

Microcephaly

Microcephaly often results from early closure of what?

Sutures

What is oligohydramnios defined as?

AFI < 5 cm

What is polyhydramnios defined as?

AFI > 24 cm

What organ fails in oligohydramnios causing Potter sequence?

Kidneys

Where is the defect located in gastroschisis?

Right of umbilicus

Is omphalocele covered by a membrane?

Yes

What are the chromosomes in a complete mole?

46 paternal only

What are the chromosomes in a partial mole?

Triploid (69)

What is fetal bradycardia defined as?

HR < 100 bpm

What is considered abnormal for a large yolk sac?

> 6 mm

What is the appearance of hemivertebrae?

Wedge-shaped vertebra

Kyphosis is a curvature in what direction?

Forward

Scoliosis is a curvature in what plane?

Lateral

What is the key difference between hydranencephaly and anencephaly?

Hydranencephaly has a skull; anencephaly does not.

What is the difference between hydrocephalus and hydranencephaly?

Hydrocephalus has a cortex; hydranencephaly does not.

What is the difference between cephalocele and cystic hygroma?

Cephalocele has a skull defect.

What is the difference between Dandy-Walker and an arachnoid cyst?

Dandy-Walker communicates with the 4th ventricle.

What is the difference between holoprosencephaly and severe hydrocephalus?

Holoprosencephaly lacks falx.

What structure separates the brain hemispheres?

Falx cerebri.

What does the absence of falx indicate?

Holoprosencephaly.

What is a sign of corpus callosum agenesis?

Teardrop ventricles.