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