IN THE NAME OF GOD. PLACENTA DR.E. ZAREAN Zygote

IN THE NAME OF GOD

PLACENTA DR.E. ZAREAN

ZygoteZygote

Pregnancy: Level 1

•Fertilisation•Cell division

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First week

•Fertilisation•Cell division•Wafted along Fallopean tube into uterus

(or Oviduct)

• This This cleavagecleavage starts within starts within 24 hours of 24 hours of fertilizationfertilization and occurs nearly and occurs nearly every 12 every 12 hourshours repeatedly repeatedly

• The resultant The resultant 16 cells mass16 cells mass is called is called morulamorula which reaches the uterine cavity which reaches the uterine cavity after about after about 4 days4 days from fertilization. from fertilization.

Cleavage and blastocyst formation:Cleavage and blastocyst formation:

• A cavity appears within the morula converting it into a cystic structure called blastocyst.

• The cells become arranged into an :1. Inner mass (embryoblast) which will form

all the tissues of the embryo, and an 2. Outer layer called trophoblast which

invade the uterine wall.

Cleavage and blastocyst formation:Cleavage and blastocyst formation:

The blastocyst remains free in the uterine cavity for 3-4 days, during which it is nourished by

the secretion of the endometrium (uterine milk).

Cleavage and blastocyst Cleavage and blastocyst formation:formation:

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blastocyst

Endometrium

•Fertilisation•Cell division•Wafted along Fallopean tube •Implantation in uterine wall

Endometrium

CapillarySecretory duct

Trophoblast

Yolk sack

Blastocoel

BlastocystEmbryo

Uterine epitheliu

m

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Placenta formation

• Lacunae form within synctiotrophoblast--maternal blood fills these spaces

• Vili form with embryonic capillaries down middle

The decidua:The decidua:• It is the thickened vascular

endometrium of the pregnant uterus. • The glands become enlarged, tortuous

and filled with secretion. • The stromal cells become large with

small nuclei and clear cytoplasm, these are called decidual cells.

Chorion:Chorion:After implantation, the trophoblast differentiates After implantation, the trophoblast differentiates

into 2 layers:into 2 layers: a. An outer one called syncytium

(syncytiotrophoblast) which is multinucleated cells without cell boundaries,

b. An inner one called Langhan’s layer (Cytotrophoblast) which is cuboidal cells with simple cytoplasm.

• A third layer of mesoderm appears inner to the cytotrophoblast.

• The trophoblast and the lining mesoderm together form the chorion.

• Mesodermal tissue ( connecting stalk) connects the inner cell mass to the chorion and will form the umbilical cord later on.

Chorion:Chorion:

• The outer syncytium and inner Langhan’s cells form buds surrounding the developing ovum called primary villi.

• When the mesoderm invades the center of the primary villi they are called secondary villi.

• When blood vessels (branches from the umbilical vessels) develop inside the mesodermal core, they are called tertiary villi.

Chorion:Chorion:

Primary villous Secondary villousSecondary villous

Transverse section of tertiary villous

Amnion:Amnion:After implantation, 2 cavities appear in the inner cell mass; the amniotic

cavity and yolk sac and in between these 2 cavities the

mesoderm develops.

•Fertilisation•Cell division•Wafted along Fallopean tube •Implantation in uterine wall•Formation of placenta

•Supply oxygen and nutrients•Remove waste products and CO2

•Provide a barrier between mother and fetus who are

genetically and immunologically different•Endocrine organ (human chorionic gonadotrophin,

oestrogen and progesterone

Functions of the placenta

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Hormonal control of pregnancyPhase 1

•Corpus luteumOestrogen and progesteroneStimulated by luteinising hormone (LH) from

pituitary

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Trophoblast and early placentaProduces human chorionic gonadotrophin

(hCG)This has LH like effects on corpus luteum

hCG is a peptide hormoneBasis of most pregnancy tests (antibody)(appears in urine)Responsible for “morning sickness”

Also a growth hormone/prolactin analogue from trophoblast (human placental lactogen, hPL)

Increases growth of many tissues and mammary glands


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The placenta becomes the dominant source of oestrogen and progesterone

Also secreteshuman chorionic gonadotrophinhuman placental lactogen


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hCGOestrogen

Blood levels of hormones during gestation, 40 weeks

0 10 20 weeks 30 40

Blo

od

conce

ntr

ati

on

End lastperiod

Parturition

Progesterone

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hPL

0 10 20 weeks 30 40

hCG Oestrogen

Blo

od

conce

ntr

ati

on

Progesterone

hPL

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Placenta formation

• Villi bathed in maternal blood in lacunae--exchange of nutrients, O2, CO2

• After 13 weeks, full placenta--pancake-shaped organ.

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Placental Abnormalities

Abnormalities of the Membranes

Umbilical cord Abnormalities

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Normal placenta (term placenta ) diameter : 30-70 cm thickness : 2.0 ~ 2.5 cm weights : approximately 470 g (about 1 lb).

Placental and fetal size and weight roughly correlate in a linear fashion

Fetal growth depends on placental weight which is less with small- -for- gestational age infants

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Abnormality Definition Clinical significance

Multiple Placentas with a single fetus

Placenta bipartita or bilobata

- the placenta is separated into lobes

- division is incomplete and the vessels

of fetal origin extend from one lobe to

the other before uniting to form the

umbilical cord Placenta duplex, triplex

- two or three distinct lobes are separated

entirely and the vessels remain distinct.

Bilobed placenta

Succenturiate lobes

small accessory lobe ≥1, develop in

the membranes at a distant from the

periphery of the main placenta, to

which they usually have vascular

connections of fetal origin incidence : 5%

retained in the uterus

after delivery and may

cause serious hemorrhage accompanying vasa previa

- dangerous fetal hemorrhage at

delivery

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Membranaceous Placenta

all of the fetal membranes are

covered by functioning villi and the

placental develops as a thin

membranous structure occupying

the entire periphery of the chorion

serious hemorrhage d/t associated placenta previa or accreta

Ring – shaped Placenta

Placenta is annular in shape and

sometimes a complete ring of placental

tissue Variant of membraceous placenta

- tissue atrophy in a portion of the

ring a horseshoe shape in more

common Incidence : < 1/6000 deliveries

Antepartum & postpartum bleeding and fetal growth restriction

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Diagnosis Definition Clinical significance

Fenestrated Placenta Central portion of a discoidal placenta

is missing In some instances, there is an actual

hole in the placenta but more often

the defect involves only villous tissue

with the chorionic plate

mistakenly considered to indicate that a missing portion of placenta

Placenta

Accreta

Increta

Percreta

serious variations in which

trohpoblastic tissue invade the

myometrium to varying depths much more likely with placenta

previa or with implantation over a

prior uterine incision or perforation

Torrential hemorrhage

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Extrachorial Placentation

Circumvallate

Placenta

Circummarginate

placenta

When the chorionic plate, which is on the

fetal side of the placenta, is smaller than

the basal plate, which is located on the

maternal side, the placental periphery is

uncovered

Fetal surface of such a placenta presents

a central depression surrounded by a

thickened, grayish-white ring. Ring : composed of a double fold of

amnion and chorion with degenerated

decidua and fibrin in between Within the ring, the fetal surface presents

the usual appearance, except that the

large vessels terminate abruptly at the

margin of the ring

Ring dose not have the central depression with the fold of membranes

Antepartum hemorrhage

- from placental abruption

and fetal hemorrhage Preterm delivery Perinatal mortaliy Fetal malformations

less well defined

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Placental AbnormalitiesPlacental Abnormalities

Placental calcification

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Placental AbnormalitiesPlacental Abnormalities-Tumors of the Placenta--Tumors of the Placenta-

Gestational Trophoblastic Disease

Chorioangioma(Hemangioma)

Tumors Metastatic to the Placenta

Embolic Fetal Brain Tissue

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Placental AbnormalitiesPlacental Abnormalities-Tumors of the Placenta--Tumors of the Placenta-

Chorioangioma (Hemangioma) The resemblance components to the blood vessels and stroma

of the chrionic villus Benign tumors of placenta Incidence : 1% Diagnosis : larger chorioangiomas – sonographic findings Associated symptome - small growths : asymptomatic - large tumors : hydramnios or antepartum hemorrhage Complication : associated with low birthweight : fetal death and malformations are uncommon

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Chorioangioma (Hemangioma)

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Abnormalities of the Membranes

Meconium Staining

Chorioamnionitis

Other Abnormalities

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Abnormalities of the Membranes- Meconium Staining -

Incidence : %14-20 Preterm fetuses seldom pass meconium.

<38 wks : uncommon >42 wks : increase to 25~30%

Staining of the amnion can be obvious within 1~3hours after meconium passage

Although more prolonged exposure results in staining of the the chorion, umbilical cord and decidua, meconium passage cannot be timed or dated accurately .

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Incidence : %14-20 Preterm fetuses seldom pass meconium.

<38 wks : uncommon >42 wks : increase to 25~30%

Staining of the amnion can be obvious within 1~3hours after meconium passage

Although more prolonged exposure results in staining of the the chorion, umbilical cord and decidua, meconium passage cannot be timed or dated accurately .

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Study Meconium Passage(%)

Eden and associates(1987)

39weeks 14

40weeks 19

42weeks 26

>42weeks 29

Usher and colleagues(1988)

39-40 weeks 15

41 weeks 27

42 weeks or greater 32

Steer and co-workers(1989)

<36 weeks 3

36-39 weeks 13

40-41 weeks 19

42 weeks or greater 23

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Clinical significance : perinatal morbidity and mortality↑ - severe fetal acidemia (cord arterial pH < 7 )

- cesarean delivery : doubled ( 7-14%)

: neonatal morbidity and mortality ↑

- meconium aspiration syndrome (10% of exposed infants)

: serious maternal risk ↑

- associated with amnionic fluid embolism → increases maternal mortality from cardiorespiratory failure and consumptive coagulopathy

- Puerperal metritis : 4 times

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Abnormalities of the Membranes-Other Abnormalities-

Abnormalities Definition & causes Clinical significance

Amnionic cyst lined by typical amnionic epithelium fusion of amnionic folds with

subsequent fluid retention

Amnion nodosum tiny, light tan , creamy nodules in the

amnion made up of vernix caseosa

with hair, degenerated squames and

sebum Oligohydramnios

Found in fetuses with renal agenesis prolonged preterm ruptured

membranes the placenta of the donor

fetus with twin-to-twin

transfusion syndrome

Amnionic band caused when disruption of the amnion

leads to formation of bands or strings

that entrap the fetus and impair growth

and development of the involve

structure

Intrauterine amputation

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Umbilical Cord Abnormalities

Length

: appreciable variation, extremes range

- no cord(achordia) ~ lengths<300cm

- mean length : 37cm

- excessively long cords : ≥ 70cm ( ≥2 SD )

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Short umbilical cords : associated with adverse perinatal outcomes such as fetal growth restriction, congenital malformations, intrapartum distress and risk of death (doubled)

Excessively long cords : associated with - maternal systemic disease and delivery complications such as prolapse, cord entanglement, fetal distress, fetal anomalies and respiratory distress

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Determinants of cord length

- concept that cord length is influenced positively by both the

volume of amnionic fluid and fetal mobility

- heredity

Miller and associates identified the cord to be shortened appreciably when there had been either chronic fetal constraint from oligohydramnios or decreased fetal movement, such as with Down syndrome or limb dysfunction

Long cord Short cord

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Umbilical Cord Abnormalities Cord Coiling

Umbilical vessels : in a spiraled manner

Hypocoiled cords

increase in various adverse outcomes in fetuses meconium staining, preterm birth and fetal distress

Hypercoiled cords higher incidence of preterm delivery and cocaine abuse

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Umbilical Cord Abnormalities Abnormalities of Cord insertion

Cord insertion

: usually inserted at or near the center of the fetal surface of the

placenta

Furcate insertion

Marginal insertion

Velamentous insertion

Vasa Previa

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Umbilical Cord AbnormalitiesAnomalities Definition incidence Significance

Furcate insertion Umbilical vessels separate from the cord substance before their insertion into the placenta

Rare

Margnial Inserion Battledore placenta

: cord insertion at the placental

margin

7% at term Cord being pulled off during delivery of the placenta

Velamentous Insertion

Umbilical vessels separate in

the membranes at a distance

from the placental margin Reach surrounded only by a

fold of amnion

1.1% more frequently

with twins 28% of triples

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Vasa Previa Associated with velamentous insertion when some of the fetal

vessels in the membranes cross the region of the cervical os below the presenting fetal part

Incidence : 1/5200 pregnancies

- ½ : associated with velamentous inserion

- ½ : marginal cord insertions and bilobedor, succenturiate-lobed

placentas Risk factors

- bilobed , succenturiate or low-lying placenta

- Multifetal pregnancy

- Pregnancy resulting from in vitro fertilization

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Diagnosis : color Doppler examination (low sensitivity with ultrasound) - Perinatal diagnosis : associated with increased survival (97:44) - Antenatal diagnosis : associated with decreased fetal mortality compared with discovery at delivery Hemorrhage antepartum or intrapartum : vasa previa and a ruptured fetal vessel exists Detecting fetal blood - Apt test - Wright stain : to smear the blood on glass slides stain the smears with Wright stain and examine for nucleated RBC - normally are present in cord blood but not maternal blood - risk of low lying placenta : 80%

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Diagnosis : color Doppler examination (low sensitivity with ultrasound) - Perinatal diagnosis : associated with increased survival (97:44) - Antenatal diagnosis : associated with decreased fetal mortality compared with discovery at delivery Hemorrhage antepartum or intrapartum : vasa previa and a ruptured fetal vessel exists Detecting fetal blood - Apt test - Wright stain : to smear the blood on glass slides stain the smears with Wright stain and examine for nucleated RBC - normally are present in cord blood but not maternal blood - risk of low lying placenta : 80%

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Cord Abnormalities capable of impeding blood flow Knots

false Result from kinking of the vessels to

accommodate to the length of the cord

True Result from active fetal movements Venous stasis

→ mural thrombosis and fetal hypoxia,

causing death or neurological

morbidity

Incidence : 1.1%

Stillbirth incidence : 6%

esp)

high incidence : monoamnionic twins

False knot(Lt), true knot (Rt)

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Umbilical Cord Abnormalities Cord Abnormalities capable of impeding blood flow

Loops

: Coiled around portions of the fetus, usually the neck.

longer cords

- one loop of nuchal cord : 20~34%

- Two loops in 2.5 ~ 5%

- three loops : 0.2~0.5%

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Umbilical Cord Abnormalities Torsion and Strictures

Torsion Incidence : rare Result from fetal movements during which the cord normally

becomes twisted fetal circulation is compromised

Stricture More serious Most infants with this finding are stillborn Associated with an extreme focal deficiency in Wharton jelly In monoamnionic twinning, a significant fraction of the high

perinatal mortality rate is attributed to entwining of the umbilical cords before labor

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Placental AbnormalitiesPlacental Abnormalities- Abnormal Shape or Implantation-- Abnormal Shape or Implantation-

Circumvallate(left) and cricummarginate(right) variaties of extrachorial placentas

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Placental AbnormalitiesPlacental Abnormalities- Abnormal Shape or Implantation-- Abnormal Shape or Implantation-

Anomaly of Placental site

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Vasa previa

Internal cx os

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IN THE NAME OF GOD. PLACENTA DR.E. ZAREAN Zygote