Obstetrics Flashcards
At what hCG level should you expect to visualize an intrauterine gestational sac?
2000 IU
What is the optimal gestational age for the First Trimester Screen?
11 weeks 0 days to 13 weeks 6 days
What is the optimal crown rump length for the First Trimester Screen?
45-84 mm
What 4 elements comprise the First Trimester Screen?
- Fetal nuchal translucency
- Maternal age
- PAPP-A
- BhCG
Which chromosome abnormalities are assessed with the First Trimester Screen?
Trisomy 13 (Patau syndrome) Trisomy 18 (Edwards syndrome) Trisomy 21 (Down syndrome)
What are the 2 components of the serum biochemistry for the First Trimester Screen?
- Free beta hCG
- PAPP-A
What is measured during a Triple Screen? Quadruple Screen?
- AFP, unconjugated estriol, and beta-hCG
- Quad screen includes inhibin A
What findings are diagnostic of pregnancy failure (4) (NEJM 2013)?
- Crown-rump length of >= 7 mm and no heartbeat
- Mean sac diameter of >= 25 mm and no embryo
- Absence of embryo with heartbeat >= 2 wk after a scan that showed a gestational sac without a yolk sac
- Absence of embryo with heartbeat >= 11 days after a scan that showed a gestational sac with a yolk sac.
* If criteria not met, then repeat US in 7-10 days if stable
* Can follow bhCG levels too
When is the best time to do a routine anatomy scan?
18-20 weeks, favour closer to 20 weeks
At what cervical length would the obstetrician consider cerclage?
Less than 25 mm
Close follow up 25-30 mm
Greater than 30 mm is normal
How do you measure the biparietal distance?
Outer table to inner table at the level of the thalami and cavum septum pellucidum.
How do you measure the abdominal circumference?
Abdo circumference should be determined at the skin line on a true transverse view at the level of the fetal liver, just below the heart, using the landmark of the umbilical portion of the left portal vein at its junction with the portal sinus and right portal vein.
What is a normal amniotic fluid index (AFI)?
Take the largest AP fluid pocket in each quadrant; and add the four measurements together.
Normal is between 7 and 25 cm
(US Requisites)
What makes up the Biophysical Profile (BPP)?
Five tests are combined: four are of the fetus (assessing acute hypoxia) evaluating cardiac function, breathing, gross body movement, and overall tone, and one is of the amniotic fluid (assessing chronic hypoxia). The non stress test uses an external monitor to analyze cardiac function. The other four are evaluated by US. Scored from 0 to 10.
What is considered small for gestational age (SGA)?
Less than the 10th percentile for birth weight
What is the value of the BPP score?
The fetus with a BPP score of 7 or more can be considered “safe” in most cases for up to a week.
When should you be able to see a gestational sac? An embryo? A yolk sac?
- Gestational sac usually can be seen at 5 weeks GA on TVUS
- Embryo routinely seen at about 6 weeks GA on TVUS
- Yolk sac often identified at 5.5 weeks GA on TVUS
When can cardiac motion be detected?
- Transabdominally, heart motion is detected in all embryos with a CRL larger than 9 mm (6.9 weeks).
- Transvaginally, heart motion is detected in all normal embryos larger than 5 mm (6.2 weeks). In most cases it can be detected even earlier.
When does bowel normally return to the abdominal cavity in a normal fetus?
by 12 weeks
What is the classic clinical triad for hydatiform mole?
1) enlarged uterus
2) hyperemesis
3) Beta hCG markedly elevated (often >100,000 mIU/L)
T or F. A partial mole is usually triploid.
True
Choroid plexus cysts should raise suspicion for which disease?
Trisomy 18. Other findings include: cardiac anomalies, clenched hands (especially with overlapping index finger), a small or absent nasal bone, and a cleft lip/palate.
What are typical US findings of trisomy 21?
Minor markers for trisomy 21 include nuchal fold thickening and echogenic spots in the bowel or heart. Other markers include clinodactyly, not clenched hands as seen here.
Major anomalies in trisomy 21 include cardiac defects, as well as duodenal atresia and esophageal atresia.
What are typical US findings of trisomy 13?
- The hallmark brain finding in T13 is holoprosencephaly.
- Fetuses with T13 are more likely to have a midline or bilateral cleft lip/palate, rather than the unilateral cleft lip/palate.
- The typical hand finding for T13 is polydactyly, not clenched hand with overlying index finger.
- Rocker-bottom or clubbed feet
- Cardiac defects are common (50%). Hypoplastic left heart or ventriculoseptal defect
- Abdo findings: enlarged and echogenic kidneys with or without hydro, omphalocele, bladder extrophy, and echogenic bowel
- Single umbilical artery and papillary muscle calc have also been reported.
What are typical US findings of Turner syndrome?
The hallmark anomaly for Turner Syndrome is cystic hygroma. Fetuses with Turner syndrome most often also have hydrops fetalis in addition to other anomalies such as cardiac defects and horseshoe kidney.
Choroid plexus cysts can be a marker for which trisomy?
Trisomy 18
Absolute values for 11-14 week nuchal translucency?
3 mm (95th percentile)
3.5-4 mm (99th percentile)
Even those with increased NT, majority have a normal outcome.
What is the appearance of fetal hydrops?
Accumulation of fluid in >= 2 areas
-subcutaneous edema, pleural fluid, ascites
What is the single most effective marker for T21 in the 2nd trimester?
absent nasal bone (increased risk 83X)
Hypoplastic nasal bone increases risk to ~60%
At what age can an omphalocele be diagnosed?
Fetus must be >12 weeks to rule out physiological herniation. Gastroschisis can be diagnosed before 12 weeks however.
What is normal nuchal fold thickness at 18-20 weeks?
An abnormal value is one that is >5-6 mm in thickness:
- nuchal thickness should not be measured after 20.6 weeks
- NF >5 mm: sensitivity 15%, specificity 97%, PPV 8%, NPV 99% for trisomy 21 9
- NF >6 mm: sensitivity 12%, specificity 99%, PPV 13%, NPV 99% for trisomy 21 9
- ->Radiopaedia
DDx thick nuchal translucency (measured between 11-14 weeks)
- Trisomy 13, 18, 21
- Turner syndrome (XO)
DDx posterior fetal neck mass
- Cystic hygroma (septated cyst)
- Cephalocele (intracranial tissue)
- Teratoma (solid/calcifications)
- Meningocele (spine defect)
What are the types of CPAM?
Type 1: most common; 2-10 cm cyst; best prognosis
Type 2: cysts
DDx cystic chest mass
- CPAM (unilateral)
- Congenital diaphragmatic hernia (unilat, left)
- Neurenteric cyst
- Bronchogenic cyst
- Esophageal duplication cyst
DDx solid chest mass
- CPAM (Unilateral)
- CDH (unilat, left)
- Sequestration (LLL)
- CLE (UL)
- Laryngeal atresia
DDx for polyhydramnios (AFI > 20 cm)
- Idiopathic (33%)
- Macrosomia +/- diabetes (25%)
- Multiple gestations (10%)
- Fetal (anomalies 20%, hydrous 12%)
What are associated findings with multi cystic dysplastic kidney?
- Absent amniotic fluid (oligohydramnios)
- pulmonary hypoplasia
- not usually a/w abnormal karyotype
- Unilateral –> no problem –> atrophy with time
What are US findings of Down syndrome (Trisomy 21)?
Head and Neck:
- Absent/hypoplastic nasal bone
- Incr’d nuchal translucency (>3mm) (11-14 wks)
- Incr’d nuchal fold (>6 mm) (16-20 wks)
Cardiac:
- Echogenic focus
- AV canal abnormality
GI/GU:
- Duodenal atresia, echogenic bowel
- Pelviectasis
Skeletal:
-short femur or humerus
What are US findings in trisomy 18?
- Choroid plexus cysts
- Strawberry-shaped skull
- Clenched hands, overlapping digits
- Club/rocker bottom feet
What are US findings in Trisomy 13?
- Holoprosencephaly
- Facial anomalies: hypotelorism, proboscis
DDx ventriculomegaly (> 10 mm width)
- Chiari II
- Dandy Walker
- Aqueductal stenosis
- Intracranial hemorrhage
- Encephalocele
DDx oligohydramnios
“DRiPS”
- Distress/Death (fetal)
- Renal (decreased fetal urine output)
- Post dates / post maturity pregnancy /pre-eclampsia / placental insufficiency
- Spontaneous rupture of membranes (most common)
DDx large echogenic kidneys
- ARPKD
- Meckel Gruber Syndrome
- Trisomy 13
DDx large echogenic kidneys
- ARPKD
- Meckel Gruber Syndrome
- Trisomy 13
DDx polyhydramnios
-Twins
-Idiopathic (34%)
-Maternal causes: DM (24.6%), Rh income, placental tumors
-Fetal anomalies:
—Congenital anomalies (20%)
—Erythroblastosis fetalis (11.5%)
—Chromosomal disorder (10-11%)
(GI tract, NTDs, chest anomalies, skeletal dysplasia, cardiac anomalies, GU)
What is associated with strawberry-shaped skull?
Trisomy 18. Strawberry shaped calvarium is considered to be secondary to hypoplasia of the frontal lobes of the rain. Other findings: choroid plexus cysts, limb anomalies include rocker-bottom feet, clubbed feet, and overlapping fingers.
What are the most common CNS malformations associated with a “lemon head”?
Myelomeningocele with associated Chiari II malformation; encephalocele
Which syndrome can be a/w a “cloverleaf skull”?
Thanatophoric dysplasia
DDx fetal intrahepatic calcification
- idiopathic
- ischemic hepatic necrosis
- intrauterine infection
- neoplasm if associated with a mass
- rarely portal vein calcification
Classification of cleft lip and palate?
- type 1: cleft lip alone
- type 2: unilateral cleft lip and palate
- type 3: bilateral cleft lip and palate
- type 4: midline cleft lip and palate
- type 5: facial defects associated with amniotic bands or limb-body-wall complex
- ->Types 4 and 5 are a/w other anomalies and a fatal outcome.
DDx absent fetal stomach
- Esophageal atresia (a/w polyhydramnios)
- CDH
- oligohydramnios
- situs abnormality
- impaired swallowing (CNS abnormality, facial cleft, neuromuscular disorder, neck/chest mass, narrow chest)
What is Spalding sign?
Overlapping of calvarial sutures; associated with demised fetus as the calvarium collapses.
DDx skull demineralization
- Osteogenesis imperfecta (types 1 and 4 AD and nonlethal) (types 2 and 3 are more severe)
- congenital hypophophatasia
- achondroplasia
What is the risk of heterotopic pregnancy?
1 in 30,000.
Can be as high as 1 in 3000 in high risk groups (assisted reproduction, IUCD, previous tubal surgery and PID)
May be as high as 3% in women undergoing ART.
Classic appearance of a cystic hygroma in the neck?
Main ddx?
- A spoke-wheel appearance of septations is pathognomonic.
- For an encephalocele, a cranial defect and CNS abnormalities are associated.
Tx for cervical ectopic pregnancy?
- Methotrexate, dilatation and evacuation following uterine artery ligation or ultrasound-guided potassium chloride injection
- Must differentiate b/w cervical ectopic and abortion in progress. Tx of a cervical ectopic with D&C can result in life-threatening hemorrhage and hysterectomy.
Findings of twin-twin transfusion syndrome?
-Monochorionic placenta, same gender, marked growth discordance (>20%), polyhydramnios in the larger twin sac and oligo in the smaller twin sac.
What is the most common fetal intracranial mass?
supratentorial teratoma
How do you distinguish between hydranencephaly and alobar holoprosencephaly?
- Hydranencephaly results from destruction of a normally formed brain and is not a/w facial abnormalities. The fall is always present.
- Lack of a flax, fused thalami and abnormal facies suggest alobar holoprosencephaly
- Holoprosencephaly is often a/w aneuploidy, especially T13 (look for polydactyly, cystic kidneys and facial anomalies)
How many abnormalities need to be present to diagnose a VACTERL association?
The VACTERL association is diagnosed when 3 or more of the defined anomalies (Vertebral, imperforate Anus, Cardiac, Tracheoesophageal fistula, Esophageal atresia, Renal/Rib/Radial ray, Limb) affect a patient; therefore, keep investigating when 1-2 of these anomalies are found. The heart and kidneys are the most commonly affected organs in this association.
DDx fetal hydrops
1) Immunologic (Rh incompatibility)
2) Non-immunologic
- high-output cardiac failure
- obstruction of venous return (e.g., congenital cystic adenomatoid malformation or congenital pulmonary airway malformation [CPAM])
- decreased plasma oncotic pressure with decreased albumin formation
- increased capillary permeability such as with a congenital infection
- obstruction of lymphatic flow (e.g. cystic hygroma)
Types of sacrococcygeal teratoma
1) Type I: predominantly external with minimal pre sacral component
2) Type II: predominantly external with significant intrapelvic component
3) Type III: predominantly internal with abdominal extension
4) Type IV: entirely internal with no external component
DDx cystic lesion in the posterior fossa
- Dandy Walker malformation (syndrome)
- Dandy Walker variant
- Mega cisterna magna
- Arachnoid cyst
- Blake’s pouch cyst
4 degrees of placenta previa
1) complete placenta previa
2) partial placenta previa
3) marginal (placental edge at the margin of the internal os)
4) low-lying placenta (within 2 cm of the internal os)
What syndromes are associated with omphalocele?
- T13
- T18
- Beckwith-Wiedemann syndrome
- pentalogy of Cantrell
- OEIS (omphalocele, exstrophy of bladder, imperforate anus, spinal defects)
- Cardiac malformation is present in 50% of neonates with omphalocele
Pentalogy of Cantrell
-Rare (6 in 1,000,000 live births)
-Consists of:
1) omphalocoele
2) ectopia cordis (abnormal location of heart)
3) diaphragmatic defect
4) pericardial defect or sternal cleft
5) cardiovascular malformations (VSD, ASD, ToF, left ventricular diverticulum)
(Radiopaedia)
How is pyelectasis defined in the second trimester?
Renal pelvis anteroposterior (AP) dimension 4 mm or
greater in transverse plane
DDx echogenic bowel
- swallowed blood (post amnio or placental abruption)
- chromosomal abn (T21, less commonly T13/T18/XO)
- infection (CMV)
- cystic fibrosis (or meconium ileus)
- bowel obstruction
- IUGR
- mesenteric ischemia
Two-vessel cord is most commonly associated with what chromosomal abnormalities?
T13 and T18
Contraindications to methotrexate treatment for ectopic pregnancy
- BhCG > 5000 IU/L
- fetal cardiac activity
- free fluid in cul-de-sac (presumably representing tubal rupture)
What is a Spalding sign?
overlapping skulls bones; indicative of fetal demise
Strawberry-shaped skull
T18
Cloverleaf skull (Kleeblattschadel)
thanatophoric dysplasia
seen with narrow, bell-shaped thorax, and shortened telephone receiver femurs
DDx lemon sign
- Encephalocele
- Chiari II malformation and myelomeningocele
- Dandy-Walker malformation
- Agenesis of the corpus callosum
- thanatophoric dysplasia
others. ..
US findings of placenta accreta (includes accreta, increta and percreta)
- complete loss of the regularity of the retroplacental sonolucency zone
- thinning of the hypoechoic uterine serosa-bladder interface
- presence of exophytic masses invading the urinary bladder
- thickened placenta with abnormal lacunae
- Color Doppler criteria include the presence of color Doppler signal within the focal lacunae and the presence of sonolucent vascular lakes with turbulence flow in the placenta
- Hypervascularity of the uterine serosa-bladder interface
US features of limb-body-wall complex
Typical ultrasound features include:
- ventral wall defects
- craniofacial defects
- scoliosis
- often associated internal malformations such as cardiac defects, absent diaphragm, and renal abnormalities
- Sometimes the fetus is so bizarre and misshapen that it almost appears as a complex mass.
- The umbilical cord is often shortened, and the fetus may be fused with the placenta
- Prognosis is uniformly fatal
- No karyotypic abnormalities associated with limb-body wall complex have been reported
DDx cystic lesion near the umbilical cord
- Umbilical cord hematoma
- Umbilical vessel dilation
- Wharton’s jelly cyst (pseudocyst)
- Allantoic cyst (true cyst)
- Omphalomesenteric duct remnant (true cyst)
Potter sequence?
- Pulmonary hypoplasia
- Oligohydramnios
- Twisted skin (wrinkly skin)
- Twisted face (Potter facies: receding/pouty chin, low-set ears)
- Extremity defects (e.g. clubfoot)
- Renal agenesis (bilateral)
What is the detection rate of Trisomy 21…
1) With Maternal age only?
2) With Maternal age and Nuchal translucency?
3) With Maternal age, Nuchal translucency and Serum biochemistry?
4) With Maternal Age, Nuchal translucency, Serum biochemistry and Nasal bone?
1) 30%
2) 70-80%
3) 80-90%
4) >95%
CHARGE association
- Coloboma
- Heart defects
- Atresia of choanae
- Retardation of growth/development
- Genito-urinary abnormalities
- Ear abnormalities
PHACES syndrome
Posterior fossa malformations Hemangioma Arterial abnormalities Cardiac defects (Coarctation of aorta) Eye abnormalities Sternal cleft and Supraumbilical raphe syndrome
What is considered normal for placental cysts (number and size)?
Normal if less than 3 in number, and less than 4 cm in size.
Otherwise, may be an indication of aneuploidy (although somewhat controversial)
What is mild polyhydramnios?
Mild Polyhydramnios
- single deepest pocket 8-10 cm
- AFI 24-31 cm
- subjective impression
What are US findings of TTTS?
General features that may suggest towards the diagnosis include:
- twin growth discordance between the two twins (>20%)
- there may be folding of the inter-twin membrane as an early sign due to disparity in amniotic fluid volumes (amniotic fluid discordance)
- in early pregnancy, there may be a difference in nuchal translucency between the twins
- significant difference in umbilical cord diameter
Features that may noted individually in each twin include:
Recipient twin:
-is larger in size and will have an increased estimated fetal weight (EFW)
-polyhydramnios
-large urinary bladder
-evidence of fetal polycythaemia
-fetal hydrous
-fetal cardiomegaly
-in certain cases fetal echocardiography may also show AV valve incompetence
Donor twin (pump twin / stuck twin)
- the small twin (with decreased EFW) can appear “pinned” to side of gestational sac
- evidence of fetal anaemia
- oligohydramnios
- small/absent urinary bladder
