Placenta
Normal
Development
8wks: focal thickening along periphery of gestational sac at site of implantation
12 wks: granular disc shape with smooth surrace of chorion
retroplacental complex of decidual and myometrial veins which can be obliterated by too much pressure. RPC is the landmark for previa, abruption and accreta
ROT: thickness [mm] = GA [wks]
Thick placenta (>4 cm)
abruption
maternal DM
Triploidy
fetal hydrops
severe maternal anemia
congenital infection
congenital fetal neoplasm
Thin placenta (<1 cm)
maternal HTN, DM, toxemia of pregnancy
trisomy 18, 13
placental insufficiency
Shape
succenturiate: accessory lobe with increased postpartum risk
circumvallate: decidua basalis larger than placenta causing raised rolled placental edges
menbranacea: thin layer covering entire uterine cavity
Battledore: marginal cord insertion
Previa
overall risk (0.6%): increased with previous C/S, multiparity, maternal age >35
risk of previa 5% when present at 12-14wks as lower uterine segment lengthens in 3rd trimester.
painless vaginal bleeding (usually 3rd trimester)
must only diagnose with empty bladder otherwise lower uterine segment gets distorted, and beware of LUS contraction pitfall by watching dynamically or repeat in 30min.
low lying < 2cm from os
marginal previa: edge reaches or partially covers a dilating cervical os
vasa previa: cord with velamentous insertion crossing the internal cervical os
Painful Vaginal Bleeding
Risk factors: HTN, smoking, cocain, toxemia
subchorionic hemorrhage: separation of placental margin with maternal venous dissection extending beneath chorionic membrane.
usually before 20wks.
seen in 25% of threatened abortion, with risk increasing if >40% of surface area dissected away
retroplacental abruption: maternal arterial bleeding below placenta with resultant disruption of the retroplacental complex. May just give appearance of thick placenta when subacute.
acute hemorrhage is anechoic, then isoechoic with clot formation, before anechoic 1-2 wks after event (hemolysis).
<50% are seen by U/S
>60cc of blood/ more than 50% of placental SA elevated carries a 75% fetal mortality
amniotic tears may be present resulting in blood into gestational sac and amniotic fluid into maternal bloodstream (risk of coagulopathy)
Creta
Risk: multiparous, previous C/S, low lying/anterior placenta +/- previa
Dx: loss of retroplacental curvilinear vessel complex, with "Swiss cheese appearance" of ++vascularity, and thinned appearance of underlying myometrium (<1mm)
accreta: chorionic villi contacting myometrium, with absent decidua basalis
increta: chorionic villi invading myometrium
percreta: chorionic villi penetrating through myometrium and invading adjacent organs (usually bladder- resulting in loss of bright reflection from bladder serosa)
Focal Placental Masses
occurs in 10% of pregnancies
Grade 0: smooth chorionic face, no echogenic foci of calcification
Grade I: suble indentations, random calcific foci
Grade II: basal layer of comma shaped calcifications
Grade III: large irregular densities with deep indentations usually with posterior shadowing
when over 38wks is 100% associated with lung maturity
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8wks: focal thickening along periphery of gestational sac at site of implantation
12 wks: granular disc shape with smooth surrace of chorion
retroplacental complex of decidual and myometrial veins which can be obliterated by too much pressure. RPC is the landmark for previa, abruption and accreta
ROT: thickness [mm] = GA [wks]
Thick placenta (>4 cm)
abruption
maternal DM
Triploidy
fetal hydrops
severe maternal anemia
congenital infection
congenital fetal neoplasm
Thin placenta (<1 cm)
maternal HTN, DM, toxemia of pregnancy
trisomy 18, 13
placental insufficiency
Shape
succenturiate: accessory lobe with increased postpartum risk
circumvallate: decidua basalis larger than placenta causing raised rolled placental edges
menbranacea: thin layer covering entire uterine cavity
Battledore: marginal cord insertion
Previa
overall risk (0.6%): increased with previous C/S, multiparity, maternal age >35
risk of previa 5% when present at 12-14wks as lower uterine segment lengthens in 3rd trimester.
painless vaginal bleeding (usually 3rd trimester)
must only diagnose with empty bladder otherwise lower uterine segment gets distorted, and beware of LUS contraction pitfall by watching dynamically or repeat in 30min.
low lying < 2cm from os
marginal previa: edge reaches or partially covers a dilating cervical os
vasa previa: cord with velamentous insertion crossing the internal cervical os
Painful Vaginal Bleeding
Risk factors: HTN, smoking, cocain, toxemia
subchorionic hemorrhage: separation of placental margin with maternal venous dissection extending beneath chorionic membrane.
usually before 20wks.
seen in 25% of threatened abortion, with risk increasing if >40% of surface area dissected away
retroplacental abruption: maternal arterial bleeding below placenta with resultant disruption of the retroplacental complex. May just give appearance of thick placenta when subacute.
acute hemorrhage is anechoic, then isoechoic with clot formation, before anechoic 1-2 wks after event (hemolysis).
<50% are seen by U/S
>60cc of blood/ more than 50% of placental SA elevated carries a 75% fetal mortality
amniotic tears may be present resulting in blood into gestational sac and amniotic fluid into maternal bloodstream (risk of coagulopathy)
Creta
Risk: multiparous, previous C/S, low lying/anterior placenta +/- previa
Dx: loss of retroplacental curvilinear vessel complex, with "Swiss cheese appearance" of ++vascularity, and thinned appearance of underlying myometrium (<1mm)
accreta: chorionic villi contacting myometrium, with absent decidua basalis
increta: chorionic villi invading myometrium
percreta: chorionic villi penetrating through myometrium and invading adjacent organs (usually bladder- resulting in loss of bright reflection from bladder serosa)
Focal Placental Masses
occurs in 10% of pregnancies
- Calcific foci: occurs in smokers and patients on heparin. -of no clinical significance
- small hematoma/cystic degeneration: subchorionic fibrin deposition -not significant even if large deposits
- Chorangioma:
hemangioma of the placenta. Present in 1% of pregnancies
Pulsates at fetal heart rate
if large, can cause shunting, IUGR, hydrops, polyhadramnios, or bleeding - Mets: breast, melanoma
- Rare: placental teratoma
Grade 0: smooth chorionic face, no echogenic foci of calcification
Grade I: suble indentations, random calcific foci
Grade II: basal layer of comma shaped calcifications
Grade III: large irregular densities with deep indentations usually with posterior shadowing
when over 38wks is 100% associated with lung maturity
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