abnormalities of cord & placenta
TRANSCRIPT
ABNORMALITIES OF CORD AND PLACENTA
Dr. RAMA THAKUR
Most placentae are either round or oval.
Variations are comman – Multiple placentae with a single fetus Cord insertion between 2 placentae :
either into the chorionic bridge / into the membranes
Abnormal Placentation
Bilobed or placenta bilobata Placenta succenturata Placenta memranacea Ring shaped placenta Placenta fenestrata Extrachorial placenta
-circumvallate placenta -Placenta marginata
Abnormal Placentation
Multilobed placenta Bilobed or placenta bilobata
› Incidence 2-8% of placentas› Roughly equal size lobes are separated by
a segment membranes› Umbilical cord may insert in either of the
lobes or in velamentous fashion or in between the lobes
BILOBATE PLACENTA
Also known as bipartrite placenta or placenta duplex
Placenta containing 2 or more lobes is rare & is called Multilobate placenta.
Succenturiate lobe Incidence :5% Small accessory lobes develop at a
small distance from the main placenta. 2 fold increase in twin placentae Accessory lobe may be retained after
delivery causing PPH Accompanying vasa praevia may cause
fetal hemorrhage (APH) If the communicating membranes do
not have vessels it is called placenta supuria.
Succenturiate placenta
Pathogenesis: Abnormal placentation- Arise due to implantation in areas of
decreased uterine perfusion- Lateral implantation in between anterior
and posterior walls of the uterus with one lobe on the anteriors and one on the posterior wall
Other local factors leading to multilobulation:
› Implantation over leiomyomas› Area of previous surgeries› In the cornu› Over the cervical os
› Succenturate lobe : Results when one or more small accessory lobes are developed in the membranes at the a distance from the periphery of the main placenta
PLACENTA MEMBRANACEA
Whole/large part of placenta is covered by functioning villi , large & thin placenta ; may be associated with praevia or accereta.
RING SHAPED PLACENTA Incidence 1:6000
deliveries Annular in shape May be horse-shoe shaped
because of atrophy of a part of placental ring.
Complete ring of placental tissue may be present .
May be associated with - APH - PPH - IUGR
Placenta Fenestrata
Rare anomaly Central portion of discoid placenta is
missing. Rarely there may be an actual hole in placenta.
More often the defect involves the villous tissue & the chorionic plate remains intact.
Clinically it may prompt a search for a retained placental
EXTRACHORIAL PLACENTA
Chorionic plate (fetal side ) is smaller than basal plate .
So membranes are not inserted at the periphery of placenta.
These may be fibrin deposition in b/w the membranes.
There may be plication or folding of membranes ( circumvallate placenta)
In placenta circummarginata there is no folding of membranes
CIRCUMVALLATE PLACENTA Fetal surface has a
central depression surrounded by thickened grey white ring composed of a double fold of chorion, amnion, degenerated decidua & fibrin deposits .
Large vessels terminate at the margins of the placenta when seen from the fetal surface.
Risks of circumvallate placenta APH Fetal Hemorrhage PT delivery Placental insufficiency Perinatal mortality PLACENTA ACCERATA , INCRETA &
PERCRETA Abnormalities are serious variations. Trophoblastic cells invade the
myometrium to varying depths.
Placenta Accreta, increta, & percreta
Placenta accreta› Accounts for 75-78%› Placenta attached directly to the muscles of
the uterine wall Placenta increta
› Accounts for 17% of cases› Placenta extends into the uterine muscles
Placenta percreta› 5-7% placenta extends through the entire wall
of the uterus
Placenta accreta
Incidence of 1 in 7,000 deliveries Incidence maybe increase because of
the increase no. of women with prev CS Risk factors:
› Placenta previa› Placental located underlying the previous
uterine scar› Multiple pregnancies› Prev. D & C
Torrential hemorrhage is a frequent complication.
Placental infarcts
¼ of term pregnancies 2/3 pregnancies complicated by severe
HPNsive disease Result from occlusion of maternal vascular
supply Principal histopath features:
› Fibrinoid degeneration of trophoblast› Calcification› Ischemic infarction from adhesion of spiral
arteries
CIRCULATORY DISTURBANCES
Placental perfusion disorders many disrupt blood flow.
a) To the placentab) With in placentac) To the fetus through the villi. Many of
these lesions are found in normal mature placenta
Functional reserve of placenta is great. It may loose 30% of it’s villi without any fetal effects.
Maternal floor infarcts: Deposition of dense fibrinoid layer on
placental basal plate thick white & fibrin corrugated surface
acts as a blockade to blood flow. Associated with: IUGR PT Labor Still births May recur in
subsequent pregnancies. Etiology is not well defined. May be associated with maternal
thrombophillias.
Degenerative lesions of placenta have 2 etiological factors:› Changes assoc with aging of trophoblast› Impairment of uteroplacental circulation
causing infarction
Placental calcification
Small calcareous nodules or plaques frequently observed on the maternal surface of the placenta
Visualized in USG >33 weeks POG
› More than half of the placenta have some degree of calcification w/c increase until term
Villous (fetal) artery thrombosis
Thrombosis of a stem artery produces sharply demarcated area of avascularity
Single artery thrombosis› (+) 4.5% of placenta from normal
pregnancy› (+)10% involving diabetic women
Thrombosis of single fetal stem artery will deprive only 5% of the villi of their blood supply
Abnormalities of umbilical cord
Length› Mean length at term 50-60 cm› Vascular occlusion by thrombi & true knots› Excessively short umbilical cords may be
instrumental in abruptio placenta & uterine inversion
› Short cords are associated with› - IUGR & OLIGOHYDRAMNIOS› - CMF & CHROMOSOMAL ABERRATIONS› - Intrapartum fetal death› - 2 folds risk of death
Abnormalities of umbilical cord
Long cords are associated with- Cord entanglement Cord prolapse CMF FETAL DISTRESS& DEMISE
Cord diameter
Lean cords are associated with IUGR Large diameter cords are associated
with macrosomia Clinical utility of parameter – unclear
Umbilical cord coiling
Cord vessels spiral through the cord UCI - is the no. of complete coils
divided by the cord length in cm Antenatal UCI has the lower sensitivity
than the measurement postpartum Hyper coiling is linked with fetal
demise, IUGR & intrapartum hypoxia Abnormal UCI has been related to
trisomies & single umbilical artery
Umbilical cord coiling
Abnormalities of vessel number
Single umbilical artery : Results due to atrophy of the
previously existing umbilical artery
4 vessel cord : - Quiet uncomman - May be a venous remnannt - Association with CMF is not clear
Single umbilical artery Absence of one umbilical artery
INCIDENCE : - 0.63 % in live births - 1.92 % in perinatal deaths - 3 % in twinsIncidence is increased in women with :
Diabetes Epilepsy
PETAPHOligohydramniosHydramniosChromosomal abnormalities
Single umbilical artery & CMFAbout 30% of all infants with only one umbilical
artery have congenital anomalies› Associated CMF : › Aneuploidies Tracheo-oesophagial fistula
Renal agenesis Imperforate anus› Vertebral defects› 34% are growth restricted› 17% deliver preterm
Fused Umbilical Artery
Rarely umbilical artery may fail to split Shared ,fused lumen May involve the entire length or may
be partial (towards the placental insertion site)
Hyrtl Anastomosis : Anastomosis b/w the two umb. Arteries
with in 3 cm of placental incertion siteActs as a pressure equalising system b/w the
two umbilical Aa. Improves placental perfusion during uterine
contractions /during compression of one of the umbilicalarteries.
Abnormalities of cord insertion
Usually the cord is inserted at or near the center of the fetal surface of placenta.
Various cord insertion variations are:› Battledore placenta› Furcate insertion› Velamentous insertion› Vasa praevia
Battledore placenta
Furcate Insertion
Insertion site is normal
Umbilical vessels lose their protective wharton’s jelly shortly before insertion.
Vessels are covered only by the amnion(vulnerable to compression)
Velamentous insertion of umbilical cord
An abnormal condition in which umbilical vessel does not insert into the placental mass but instead, traverse the fetal membrane at a short distance from the placental margin.
They are surrounded only by a fold of amnion(vulnerable to
compression).
More common with placenta praevia and multiple pregency
Incidence :› 1.1% in singleton pregnancies› 8.7% in twin gestations› Spontaneous abortion
- 33% between 9th & 12th wks AOG- 26 % between 13th & 16th
Vasa previa
Incidence : 1 in 5200 pregnancies
Assoc with Velamentous insertion when some of the fetal vessels in the membrane cross the region of the internal os & occupy a position of the presenting part
These vessels are not only vulnerable to compression but also to laceration.
Vasa previa : risk factors
Bilobate placenta Succenturiate placenta 2nd trimester placenta praevia Pregnancies conceived by IVF
Haemorrhage from vasa praevia may leadto instant fetal death and should always be kept as aD/D in all cases with APH / IPH
Elective CS is planned in case diagnosis isconfirmed .
Vasa praevia : Diagnosis
Identified as echogenic parrallel / circular line near the cervix
USG has low sensitivity
Doppler is recommended in suspected cases
Vasa previa
Cord abnormalities Knots : False knots
- Result from kinking of the vessels to accommodate length of cord and are due to redundancies of Umbilical vessels / Wharton’s jelly.
Cord abnormalities True knots
- Results from active fetal movement
Cord knots: True knots
Incidence 1% More common in monoamniotic twins Active fetal movements create true
knots Risk of still births is increased 5 to 10
folds in those with true knots. FHR abnormalities are common during
labor but cord blood PH values are normal
Cord loops: The cord is frequently coiled around the fetus
More likely with longer cords
Loops around fetal neck are termed a nuchal cord (uncommon cause of adverse PN outcome)
Contractions may compress the nuchal cord and cause FHR decelerations and low umbilical artery
Incidence : › 1 loop of Nuchal cord 20-34%› 2 loops of nuchal cord 2.5-5%› 3 loops of nuchal cord 0.2-0.5%
Cord hematoma
Associated with-› Short cord› Trauma› Entanglement
May result from rupture of varyx(venous)
May be iatrogenic
Cord cysts
May be found along the course of the cord True cysts:
› Epithelium lined› Remnants of the allantois› Coexist with patent urachus
False Cysts: Due to degeneration of wharton’s jelly. Single cyst may resolve completely Multiple cysts may be associated with miscarriage /aneuploidy.
Cord stricture
Focal narrowing of cord diameter near fetal insertion
Pathological findings- absent of wharton’s jelly and stenosis of cord vessels.
Most cases are still borns.
Cord torsion
Hematoma› Usually results from rupture of varix,
usually of umbilical vein with effusion of blood into cord
Stricture› Most but not all infants with cord stricture
are stillborn› Assoc with an extreme focal deficiency in
wharton’s jelly
Abnormalities of fetal mambranes & amniotic fluid
Meconium staining› Staining of amniotic membrane within 1-3
hrs after meconium passage› Neonatal mortality rate
- 3.3% in the group with meconium-stained membrane compared with 1.7% in those without staining