OB Flashcards
At what beta should gestational sac be seen?
1500 (approx. 5 weeks)
When is normal yolk sac seen?
5.5 weeks
When should fetal heart activity be seen?
CRL 7 mm
Findings definitive for pregnancy failure
CRL > 7mm, no heartbeat
MSD >25 mm, no embryo
Absence of embryo >2 weeks after sac with no yolk sac
Absence of embryo >11 days after sac with yolk sac
Findings suspicious for pregnancy failure
CRL < 7mm, no heartbeat MSD 16-24, no embryo Empty amnion Enlarged yolk sac (>7mm) Small sac in relation to embryo
Locations of ectopic pregnancy in order of prevalence
*Tubal most common! (95%)
Ampulla»_space;> isthmus > fimbria > interstitial > ovary
Other sites rare: abdominal, c-section scar, cervical
Which type of ectopic has greatest risk of bleeding
Interstitial
Differences b/w complete and partial molar preg
Complete: Most common, no fetal parts, loss of egg DNA prior to fertilization, diploid karyotype 46XX (90%) or 46XY, higher bHCG, may progress to invasive mole or choriocarcinoma
Partial: Some fetal parts, two sperm fertilizing 1 egg, triploid karyotype 69XXX, XXY, XYY, lower bHCG than complete
Imaging findings in GTD
Partial mole: enlarged placenta, cystic spaces, empty sac containing abnormal fetal parts +/- hydropic degeneration
Complete mole: enlarged uterus, multiple cystic spaces (snow storm or bunch of grapes), theca lutein cysts**
Choriocarcinoma usually arises from the following:
Molar pregnancy (50%) Miscarriage (30%) Normal pregnancy (20%)
Risks of mono-di and mono-mono pregnancies
Twin twin transfusion, acardiac twins (twin reversed arterial perfusion sequences - TRAPS), twin embolization
Differentiating features between di-di, mono-di and mono-mono pregnancies on US
Di-di - 2 placentas, 2 amnions, twin peak/lambda sign
Mono-di - thin intertwin membrane
Mono-mono - no intervening membrane, intertwined cords
Normal AFI
5-25 cm (or deepest pocket 2-8 cm)
Normal NF
<6 mm
Normal cervical length
> 2.5 cm (funnelling progresses from T-Y-V-U)
RFs for placental abruption
maternal HTN, drugs, trauma, advanced maternal age
Usually late in 2nd trimester
Imaging findings placenta accreta/increta/percreta
Loss of the retroplacental hypoechoic space
Prominent venous lakes or vessels (best seen on MRI where there are abnormal vessels in myometrium)
Disruption of border between uterus and bladder (percreta)
*scarring most common cause (prior csx, d&c, pregnancies, also previa)
Findings in fetal hydrops
Ascites Pleural effusion Pericardial effusion Generalized body edema (anasarca, skin thickening) Polyhydramnios Placental enlargement Hepatomegaly
**Must have at least 2 of these findings
List the causes of fetal hydrops
Immune: Rh incompatibility
Non-immune:
- Syndromes (turners, triosmies)
- Cardiac (arrhythmia, congential heart anomalies)
- High output shunts (vein of Galen malformation, hemangiodendothelioma)
- Infection (parvovirus most common, TORCH)
- Twin twin tranfusion, TARPS
- Other: nephrotic snydrome, hepatitis, venous/lymphatic obstruction
What is Potter’s sequence?
Constellation of findings secondary to severe oligohydramnios
- Pulmonary hypoplasia
- Abnormal facies - low set ears, flattened nose, wrinkled skin, micrognathia
- Club feet, muscular contractures
Causes of polyhydramnios
50% idiopathic
others:
- primary GI obstruction/atresia
- secondary GI obstruction (hernia, omphalocele)
- CNS anomalies causing swallowing difficulties
- twin twin transfusion
- placental issues (i.e. chorioangioma)
Causes of oligohydramnios
Renal abnormalities (agenesis, ARPKD), ureter (UPJ obstruction, PUV), PROM, twin-twin transfusion
Normal ventricular size
<10 mm at atria
Which neural tube defect gives highest elevation of MSAFP
Anencephaly
Differentiating features between anencephaly and hydranencephaly
Anencephaly - no cranial vault or brain tissue above orbits, results from neural tube defect
Hydranencephaly - skull present, brain tissue replaced with fluid, often due to vascular insult
Findings in Dandy-Walker malformation
Hypoplasia of vermis
Cystic dilation of the 4th ventricle, extending posteriorly
Enlarged posterior fossa
Ddx: mega cisterna magna, Joubert (molar-tooth sign), other cystic structures in posterior fossa
Imaging findings Chiari II malformation
Intra-cranial- banana/ lemon sign, agenesis CC, absent CSP, hydro, enlarged foramen
NTD - myelomeningocele/tethered cord
Other findings: scoliosis, spinal segmentation anomalies, syrinx, club feet
Secondary signs of absent CC
- absent CSP
- teardrop lateral ventricles
- parallel ventricles
- concave margin of medial border of lateral ventricle
- midline inter-hemispheric cyst (superior herniation of 3rd ventricle)
Ddx absent CSP (high yield)
agenesis of cc
holoprosencephaly
septo-optic dysplasia
schizencephaly
Most common type of congential diaphragmatic hernia
Bochdalek; most on the left, posterolateral
Can be associated with other anomalies (cardiac) and syndromes
Differences between CPAM and sequestration
CPAM - cystic or solid appearing (type III), blood supply from pulmonary circulation, not associated with other anomalies
Sequestration - echogenic lung mass (not cystic), usually in the lower lobes (left side), systemic blood supply from aorta; can be infra-diaphragmatic
Can have combined/mixed picture (esp with CPAM and extra-lobar sequestration)
Bell shaped thorax causes
pulmonary hypoplasia (causes: mass effect from lesion such as CPAM, oligohydramnios - Potters sequences, skeletal dysplasias with short ribs)
Imaging findings in CHAOS
Bilateral, enlarged echogenic lungs; requires EXIT procedure for delivery
DDx for double bubble sign
Duodenal atresia, web, stenosis, annular pancreas (last 3 will have some distal gas as not complete obstruction)
DDx echogenic bowel
Down syndrome
TORCH infection
CF
Swallowed intra-amniotic blood
Differences between omphalocele and gastoschisis
O: more common, umbilical cord inserts at apex, covered in peritoneum, associated with anomalies in up to 75% of cases (cardiac, trisomies 18 & 13, Beckwith-Wiedemann)
G: paraumbilical (usually on right), no covering sac, isolated anomaly but can have associated atresias
Imaging findings ARPKD
Enlarged, echogenic kidneys (can’t see the cysts because of small size); poor prognosis
Findings in multi-cystic dysplastic kidney
Non-communicating cysts and dysplastic renal parenchyma; end result of obstructive uropathy
Findings in thanatophoric dysplasia
Most common lethal skeletal dysplasia
- narrow thoracic cavity, short ribs
- short, thick, bowed tubular bones (telephone receiver)
- soft tissue thickening in extremities
- macrocephaly, platyspondyly**
- clover leaf skull
- squared iliac bones, trident acetabula
Key imaging findings in Trisomy 21
- incr nuchal fold
- absent nasal bone
- cystic hygroma (more common in Turner syndrome)
- cardiac (VSD, ASD - primum/AVSD)
- echogenic intra-cardiac focus
- echogenic bowel
- duodenal atresia
- short femurs and humerus
- sandal gap toes
Key imaging findings in Trisomy 18
- **strawberry sign skull
- choroid plexus cysts
- **facial anomalies: cleft palate, micrognathia
- cardiac anomalies
- omphalocele
- renal: horseshoe kidneys, hydro
- **clenced hand that does not open, overlapping fingers
- **rocker bottom feet
Key imaging findings in Trisomy 13
- **holoprosencephaly
- midline facial anomalies (brain predicts face)
- cardiac anomalies
- omphalocele
- renal: horseshoe, polycystic
- **polydactyly
Key imaging findings in Beckwith-Wiedmann syndrome
- Macroglossia
- Hemihypertrophy
- Organomegaly
- Omphalocele**
- Perinatal hypoglycemia
**increased risk of childhood cancer (mainly Wilms and hepatoblastoma)
Imaging findings Meckel-Gruber
- Encephalocele
- Renal dysplasia (echogenic kidneys)
- Polydactyly
Which syndrome is most commonly associated with a cystic hygroma
Turner syndrome; also associated with trisomies
Grading of germinal matrix
1 - confined to matrix
2 - extends into ventricles, NO ENLARGED VENTRICLES
3 - extends into ventricles, ENLARGED VENTRICLES
4 - extends outside of ventricles into parenchyma
Normal placental thickness
2-4 cm
Causes of increased placental thickness
TORCH, GDM, hydrops
- with cysts: molar pregnancy, triploidy, placental mesenchymal dysplasia (Beckwith Wiedmann)
Causes of decreased placental thickness
Pre-eclampsia
IUGR
US findings morbidly adherent placenta/placenta accreta spectrum disorders
- *Gray-scale and color Doppler US - high sensitivity and specificity**
- irregular or absent retroplacental clear space
- multiple irregular placental lacunae (Swiss-cheese appearance)
- turbulent high-velocity flow deep in the placenta separate from the fetal surface of the placenta
An abnormal uterine serosa–bladder interface is reported as the US sign with the highest positive predictive value for MAP