4. Obstetrics p98-101 (Placenta and Umbilical Cord) Flashcards
Normal placenta (4)
Start to see on US at around 8 weeks (focal thickening along the periphery of the gestational sac).
Should be shaped like a disc around 12 weeks.
US: “granular” with smooth cover (chorion).
Underneath basal surface is normal retroplacental complex of decidual and myometrial veins.
Normal placenta aging
As it ages, it gets hypoechoic areas, septations and randomly distributed calcifications.
Venous lakes (2)
Incidental findings. Look like focal hypoechoic areas under the chorionic membrane or within placenta.
Can sometimes see flow within them.
Placental thickness DDx (8)
Too thin (<1cm)
- Placental insufficiency
- Maternal HTN or DN
- Trisomy 13 or 18
- Toxaemia of pregnancy
Too thick (>4cm)
- fetal hydrops
- Maternal DM or severe anaemia
- Congenital fetal cancer
- Congenital infeciton
- Placentla abruption
Variant placental morphology (6)
Bilobed placenta
- 2 equal sized lobes.
- Increased risk of type 2 vasa previa, post partum haemorrhage 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 haemorrhage from retained placental tissue
Circumvallate placenta
- Rolled placenta edges with smaller chorionic plate
- High risk for placental abruption and IUGR.
Placenta previa (3)
Low implantation of placenta, covering part or all of internal cervical os.
“Painless vaginal bleeding in third trimester”
Need to have empty bladder to see on US (full bladder creates false positive)
Placental abruption (4)
Premature separation of placenta from myometrium.
Classically Hx of maternal cocaine use. Also occurs in maternal HTN.
Subchorionic haemorrhage (marginal abruption) technically in same category.
Haematoma will appear as anechoic or mixed echogenicity beneath the placenta (often extending beneath chorion).
Buzzword - Disruption of the retroplacental complex.
Placental abruption vs Myometrial contraction/fibrois (2)
Placental abruption will DISRUPT the retroplacental complex of blood vessels.
Myometrial contractions/fibroids will DISPLACE the retroplacental complex.
Placenta creta (4)
Abnormal insertion of placenta, invading the myometrium.
Risk factors include prior C-section, placenta previa, advanced maternal age.
Sonographic appearance varies, depending on severity, but generally speaking includes “moth eaten” or “swiss cheese” appearance of placenta, into myometrium, (with turbulent flow on Doppler) and thinning of myometrium.
Can cause life threatening bleeding, sometimes needing hysterectomy.
Placenta Creta - spectrum (3)
Placenta Accreta - commonest (75%), mildest. Villi attach to the myometrium without invading
Placenta Increta - Villi partially invade the myometrium
Placenta Percreta - Villi penetrate through the myometrium or beyond serosa, sometimes invasion of bladder or bowel
Placenta Chorioangioma (4)
Essentially a hamartoma of the placenta, most common benign placental tumour.
Usually well circumscribed, hypoechoic masses near cord insertion.
Flow within the mass pulsatile at foetal heart rate is diagnostic (perfused by foetal circulation).
Usually harmless, but if large (>4cm) and multiple, can sequester platelets and cause high output failure (hydrops).
Placental chorioangioma vs placental hamartoma
Chorioangioma has pulsating doppler flow, hamartoma doesn’t.
Umbilical cord - normal
Normal cord should have 3 vessels (2 arteries, 1 vein).
2 vessel cord (3)
Normal variant, seen in 1%. Usually left artery is missing.
More common in twin pregnancies and maternal diabetes.
Also associated with chromosomal anomalies and foetal malformations.
Velamentous cord insertion (3)
Cord inserts into foetal membranes outside placental margin, then travels back through membranes to the placenta (between amnion and chorion).
More common with twins.
Increases risk of IUGR and growth discordance among twins.
