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Placenta & Fetal Membranes

• Chorion

• Decidua



Chorion

• The chorion is the portion of fetal membrane

that eventually forms the fetal side of theplacenta.

• The chorion is one of the membranes thatexists during pregnancy between thedeveloping fetus and mother.

• It is formed by extraembryonic mesoderm and the two layers of trophoblast andsurrounds the embryo and other membranes.



It is formed by extraembryonic mesoderm

and the two layers of trophoblast and surroundsthe embryo and other membranes.



The chorion develops

from extraembryonic

mesoderm.

Each blastocyst develops

one chorion.

The chorion is dividedinto the smooth chorion

and the villous chorion.

The villous chorion forms

the placenta



• The chorionic villi emerge from the

chorion, invade the endometrium, and

allow transfer of nutrients from maternal

blood to fetal blood.



• The chorion undergoes rapid proliferation andforms numerous processes, the chorionic villi,which invade the uterine decidua.

• Blood is carried to the villi by the branches of theumbilical arteries, and, after circulating throughthe capillaries of the villi, is returned to theembryo by the umbilical veins.

• Until about the end of the second month ofpregnancy, the villi cover the entire chorion, andare almost uniform in size; but, after this, theydevelop unequally.



Clinical significance CVS

• CVS (chorionic villus sampling) : The chorioncontains chorionic villi, which are small finger-likeprojections. These villi are snipped or suctioned off for study in the procedure.

• Since the chorionic villi are of fetal origin,examining samples of them can provide thegenetic makeup of the fetus.

• This test is performed to identify congenitaldefects. Experts use the sample to study the DNA,chromosomes, and enzymes of the fetus.

• The test can be done before amniocentesis, about10 to 12 weeks after a missed period.



Decidua • Decidua refers to the gravid endometrium - the functional layer of the

endometrium in a pregnant woman.Or,

• Decidua is the term for the endometrium during a pregnancy, which formsthe maternal part of the placenta.



• The three regions of the decidua are named according totheir relation to the implantation site

– The decidua basalis is the part of the decidua deep to theconceptus that forms the maternal part of the placenta

– The decidua capsularis is the superficial part of the deciduaoverlying the conceptus

– The decidua parietalis is all the remaining parts of the decidua



The decidua basalis is the part of the deciduadeep to the conceptus that forms the maternal

part of the placenta



Placenta

• The placenta is

the primary site of

nutrient and gas

exchange between

the mother and

fetus.



Development of Placenta

• By the end of the third week, the anatomical

arrangements necessary for physiological

exchanges between the mother and her embryo are

established.

• A complex vascular network is established in the

placenta by the end of the fourth week, which

facilitates maternal-embryonic exchanges of gases,

nutrients, and metabolic waste products.



• Chorionic villi cover the entirechorionic sac until the beginningof the eighth week .

• As this sac grows, the villiassociated with the deciduacapsularis are compressed,reducing the blood supply to

them.

• These villi soon degenerate,producing a relatively avascular bare area, the smooth chorion.



• As the villi disappear,those associated with the

decidua basalis rapidly

increase in number,branch profusely, and

enlarge

• This bushy part of the

chorionic sac is the villous

chorion.



• Growth in the size and thickness of the

placenta continues rapidly until the fetus is

about 18 weeks old (20 weeks' gestation)

• The fully developed placenta covers 15 to

30% of the decidua and weighs about one-

sixth that of the fetus.



The fully developed

placenta covers

15 to 30% of the decidua



The placenta has two parts• The fetal part of the placenta :

– Formed by the villous chorion

– The chorionic villi that arise from it project into the intervillous spacecontaining maternal blood

• The maternal part of the placenta : – Formed by the decidua basalis, the part of the decidua related to the

fetal component of the placenta

– By the end of the fourth month, the decidua basalis is almost entirelyreplaced by the fetal part of the placenta.



Fetomaternal junction

• The fetal part of the placenta(villous chorion) is attached tothe maternal part of theplacenta (decidua basalis) bythe cytotrophoblastic shell -the external layer of trophoblastic cells on thematernal surface of theplacenta.

cytotrophoblastic shellUterus

fetal part of the placenta

maternal part of the placenta



• The chorionic villi attach firmly to thedecidua basalis through thecytotrophoblastic shell and anchor thechorionic sac to the decidua basalis.

• Endometrial arteries and veins pass freelythrough gaps in the cytotrophoblastic shelland open into the intervillous space.



•Endometrial arteries and veins pass freely through gaps inthe cytotrophoblastic shell and open into the intervillousspace.



Placental circulation• The branched chorionic villi of placenta provide a large surface

area where materials may be exchanged across the very thinplacental membrane interposed between the fetal and maternalcirculations.

• It is though the numerous branch villi, which arise from stem villi,

that the main exchange of material between mother and fetustakes place.

• The circulations of the fetus and the mother are separated bythe placental membrane consisting of extrafetal tissues.

Placental circulation• Fetal Placental Circulation

• Maternal placental circulation



Fetal Placental Circulation

• Poorly oxygenated blood leaves the fetusand passes through the umbilical arteries to theplacenta.

• At the site of attachment of the umbilical cordto the placenta, these arteries divide into

several radially disposed chorionic arteries thatbranch freely in the chorionic plate beforeentering the chorionic villi.



• The blood vessels form an extensive arterio-capillary-venous system within the chorionicvilli, which brings the fetal blood extremely closeto the maternal blood.

• There is normally no intermingling of fetaland maternal blood.

• However, very small amounts of fetal blood mayenter the maternal circulation when minutedefects develop in the placental membrane.



• The well-oxygenated fetal blood in the fetalcapillaries passes into thin-walled veins that followthe chorionic arteries to the site of attachment of the umbilical cord.

• They converge here to form umbilical vein

• This large vessel carries oxygen-rich blood to thefetus.



Maternal placental circulation

• The maternal blood in the intervillous space istemporarily outside the maternal circulatorysystem.

• It enters the intervillous space through 80 to 100spiral endometrial arteries in the decidua basalis.

• These vessels discharge into the intervillous

space through gaps in the cytotrophoblastic shell.



• The blood flow from the spiral arteries ispulsatile and is propelled in jetlike fountains

by the maternal blood pressure.

• The welfare of the embryo and fetus

depends more on the adequate bathing

of the branch villi with maternal blood than on any other factor .



• Reductions of uteroplacental circulation result in

fetal hypoxia and IUGR.

• Severe reductions of uteroplacental circulationmay result in fetal death.

• The intervillous space of the mature placentacontains about 150 ml of blood that is

replenished three or four times per minute.



Placental membrane

• The placental membrane separates maternalblood from fetal blood.

• A wide variety of substances freely cross the

placental membrane. Some substances thatcross can be either beneficial or harmful.

• The composition of the placental membranechanges during pregnancy.



A. In early pregnancy, the placental membrane hasfour layers:

• Syncytiotrophoblast

• Cytotrophoblast

• Connective tissue, and• Endothelium of fetal capillaries

Hofbauer cells (large, sometimes pigmented,elliptical cells found in connective tissue) aremost numerous in early pregnancy and havecharacteristics similar to those of macrophages.



B. In late pregnancy,

the placental

membrane has two

layers:

• Syncytiotrophoblast

and

• Endothelium of fetal

capillaries.



FUNCTIONS OF PLACENTA

• The placenta has three main functions

– Metabolism

– Transport of gases and nutrients

– Endocrine secretion



Placental Metabolism

• The placenta, particularly during earlypregnancy, synthesizes glycogen,cholesterol, and fatty acids, which serve

as sources of nutrients and energy for theembryo.

• Many of its metabolic activities are criticalfor its other two major placental activities(transport and endocrine secretion)



Placental Transfer

• Transport across the placental membrane is by one of the

following four main transport mechanisms – Simple diffusion

– Facilitated diffusion

– Active transport

– Pinocytosis (is a form of endocytosis in which smallparticles are brought into the cell which subsequentlyfuse with lysosomes to hydrolyze, or to break down, theparticles)

• Oxygen, carbon dioxide, and carbon monoxide crossthe placental membrane by simple diffusion.

• Amino acids are actively transported across the placentalmembrane and are essential for fetal growth.



Other methods of placental transfer

• RBC can move across through microscopic breaksin the placental membrane

• Transport of cells across the placental membrane

under their own power – Maternal leukocytes and Treponema pallidum.

• Some protozoa such as Toxoplasma gondii infect

the placenta by creating lesions and then cross theplacental membrane through the defects that arecreated.



RBC can move

across through

microscopicbreaks in the

placental

membrane



Nutritional Substances

• Water is transported by simple diffusion.

• Glucose produced by the mother and placenta is quicklytransferred to the fetus by diffusion.

• Among lipids only free fatty acids are transported acrossthe placenta.

• Vitamins cross the placental membrane and are essentialfor normal development.

• Water-soluble vitamins cross the placental membranemore quickly than fat-soluble ones.



Maternal Antibodies

• Passive immunity is conferred upon the

fetus by the placental transfer of maternal

antibodies.

• Gamma globulins, such as the IgG classare readily transported to the fetus by

pinocytosis.



• Maternal antibodies confer fetal immunity tosome diseases such as diphtheria, smallpox,and measles.

• However, no immunity is acquired to pertussis(whooping cough) or varicella (chickenpox)

• Hemolytic disease of the newborn or erythroblastosis fetalis – Rh positive fetus and Rh negative mother.



Erythroblastosis fetalis

• The Rh factor in red blood cells (RBCs) isclinically important in pregnancy. If the mother isRh-negative, she will produce Rh antibodies if thefetus is Rh-positive.

• This situation will not affect the first pregnancy, butwill affect the second pregnancy with an Rh positivefetus.

I th d ith Rh iti



• In the second pregnancy with a Rh-positivefetus, a hemolytic condition of RBCs occursknown as Rh-hemolytic disease ofnewborn(erythroblastosis fetalis).

• This causes destruction of fetal RBCs, whichleads to the release of large amounts of bilirubin (a breakdown product of hemoglobin).

• This causes fetal brain damage due to acondition called kernicterus, which is apathologic deposition of bilirubin in the basalganglia.

• This fetal disease ranges from mild to verysevere, and fetal death from heart failure(hydrops fetalis) can occur



If the mother is Rh-

negative, she will

produce Rh antibodies if the fetus is Rh-positive.



In the second pregnancy:

Rh-hemolytic disease of newborn.

▼

▼

This causes destruction of fetal RBCs

▼

▼

release of bilirubin.This causes fetal brain damage

(kernicterus)



• In severe hemolytic disease --- the fetus isseverely anemic and demonstrates totalbody edema (i.e., hydrops fetalis) may leadto death.

• When the disease is moderate or severe,many erythroblasts are present in the fetalblood and so these forms of the disease can

be called erythroblastosis fetalis.

• In these cases, an intrauterine transfusion is

indicate



►Total body edema ------ hydrops fetalis



Diagnosis• The diagnosis of HDN is based on history,

clinical presentation and laboratory findings:

►Clinical presentation :• heart failure with pallor, enlarged liver andspleen, generalized swelling, and respiratorydistress.

• The prenatal manifestations are known ashydrops fetalis; in severe forms this can includepetechiae and purpura.

• The infant may be stillborn or die shortly after birth



►Blood tests done on the newborn baby • D antigen of the Rhesus blood group system typing

• Biochemistry tests for jaundice

• Peripheral blood morphology shows increasedErythroblasts (also known as nucleated red blood

cells)• Positive Coombs test

► USG

►Blood tests done on the mother

• Positive Coombs test

• D antigen of the Rhesus blood group system typing



How to prevent in next pregnancy

• Rho (D) immune globulin (RhoGAM,

MICRhoGAM) is a human immunoglobulin(IgG) preparation that contains antibodiesagainst Rh factor and prevents a maternalantibody response to Rh-positive cells thatmay enter the maternal bloodstream of a Rh-

negative mother.

• This drug is administered to Rh negativemothers within 72 hours after the birth of anRh-positive baby to prevent erythroblastosisfetalis during subsequent pregnancies.

• Rhogam prevents B-cell activation andmemory cells formation.



► ABO blood group system and the D antigen of the Rhesus

blood group system typing are routine prior to transfusion.

►Suggestions have been made that women of child bearing

age or young girls (if Rh-negetive) should not be given a

transfusion with Rh-positive blood to avoid possibles

ensitization.



Waste Products

• Urea and uric acid pass through the placental membraneby simple diffusion and bilirubin is quickly cleared.

• Most drugs and drug metabolites cross the placenta bysimple diffusion, the exception being those with a

structural similarity to amino acids, such asmethyldopa.

• Some drugs cause major congenital anomalies.

• Fetal drug addiction may occur after maternal use of drugs such as heroin/morphine/cocaine and 50 to 75% of these newborns experience withdrawal symptoms.



Infectious Agents

• Cytomegalovirus, rubella and coxsackie

viruses, and viruses associated with variola,

varicella, measles, and poliomyelitis may

pass through the placental membrane andcause fetal infection.



• Microorganisms such as Treponema pallidumthat causes syphilis and Toxoplasma gondii that produces destructive changes in the brain

and eyes also cross the placental membrane

• These organisms enter the fetal blood, often

causing congenital anomalies and/or death of the embryo or fetus.

Pl t E d i O



Placenta as Endocrine Organ

The placenta produces both protein and steroid hormones as

indicated below.A. Human chorionic gonadotropin (hCG) is a glycoprotein hormone that

stimulates the production of progesterone by the corpus luteum.

B. Human placental lactogen (hPL) is a protein hormone that induceslipolysis, thus elevating free fatty acid levels in the mother; it is

considered to be the "growth hormone" of the fetus.

C. Estrone, estradiol (most potent), and estriol are steroid hormonesproduced by the placenta, but little is known about their specificfunctions in either mother or fetus.

D. Progesterone is a steroid hormone that maintains the endometriumduring pregnancy, is used by the fetal adrenal cortex as a precursor for glucocorticoid and mineralocorticoid synthesis, and is used by the fetaltestes as a precursor of testosterone synthesis.



Placenta and fetal membranes after birth

• The placenta commonly has a discoid shape, with adiameter of 15 to 20 cm and a thickness of 2 to 3 cm.

• It weighs 500 to 600 gm, which is about one-sixth the

weight of the average fetus.

• The margins of the placenta are continuous with theamniotic and chorionic sacs.

Placenta has 2 surfaces:• Maternal Surface of Placenta

• Fetal Surface of Placenta

S thA i



Umbilical

cord

Fetal surface

of placenta

Smooth

chorion

Amnion



Maternal Surface of Placenta

• The characteristic cobblestone appearance of thematernal surface is produced by slightly bulgingvillous areas – cotyledons.

• Placental studies can also determine whether theplacenta is complete.

• Retention of a cotyledon or an accessoryplacenta in the uterus may cause severe uterinehemorrhage.



Fetal Surface of Placenta

• The umbilical cord usually attaches to the fetalsurface of the placenta.

• The chorionic vessels radiating to and from theumbilical cord are clearly visible through thetransparent amnion.

• The umbilical vessels branch on the fetal surface toform chorionic vessels, which enter the chorionic villiand form the arteriocapillary-venous system.



Umbilical Cord



Umbilical Cord• The umbilical cord is the

connecting cord from thedeveloping embryo to theplacenta.

• During prenatal development,the umbilical cord comes fromthe same zygote as the fetus

and normally contains twoarteries (the umbilicalarteries) and one vein (theumbilical vein), buried withinWharton's jelly.



• The umbilical veinsupplies the fetus with

oxygenated, nutrient-rich

blood from the placenta.Conversely, the umbilicalarteries return the

deoxygenated, nutrient-depleted blood.



• The umbilical cord develops from and contains

remnants of the yolk sac and allantois (and istherefore derived from the same zygote as the

fetus).

• It forms by the fifth week of fetal development,

replacing the yolk sac as the source of nutrients for

the fetus.The cord is not directly connected to the

mother's circulatory system, but instead joins theplacenta, which transfers materials to and from the

mother's blood without allowing direct mixing.

• The umbilical cord in a full term neonate is usually



• The umbilical cord in a full term neonate is usuallyabout 50 centimetres long and about 2 centimetresdiameter.

• The umbilical cord is composed of Wharton's jelly, agelatinous substance made frommucopolysaccharides.

• It contains one vein, which carries oxygenated,nutrient-rich blood to the fetus and two arteries thatcarry deoxygenated, nutrient depleted blood away.

• Occasionally, only two vessels (one vein and oneartery) are present in the umbilical cord. This issometimes related to fetal abnormalities, but it mayalso occur without accompanying problems.

• The umbilical cord enters the fetus via theabdomen at the point which will become the



abdomen, at the point which will become theumbilicus (or navel).

• Within the fetus, the umbilical vein continuestowards the transverse fissure of the liver, where itsplits into two.

One of these branches joins with thehepatic portal vein (connecting to its left branch),

which carries blood into the liver.The second branch (known as the ductus

venosus) allows the majority of the incoming blood(approximately 80%) to bypass the liver and flow viathe left hepatic vein into the inferior vena cava,which carries blood towards the heart.

• The two umbilical arteries branch from the internaliliac arteries, and pass on either side of the urinarybladder before joining the umbilical cord.



Postnatal detachment



Postnatal detachment

• Shortly after birth, the reduction in temperaturestarts a physiological process which causes theWharton's jelly to swell and collapse the bloodvessels within.

• This, in effect, creates a natural clamp, halting theflow of blood. This physiological clamping will takeas little as five minutes if left to proceed naturally.

• Within the child, the umbilical vein and ductusvenosus close up, and degenerate into fibrousremnants known as the round ligament of the liver and the ligamentum venosum respectively.



►Part of each umbilical artery closes up (degenerating intowhat are known as the medial umbilical ligaments), while the

remaining sections are retained as part of the circulatorysystem.



• Abnormalities in umbilical Cord andPlacenta



• The attachment of the umbilical cord to theplacenta is usually near the center of thefetal surface of placenta but it may attach atany point.

• Example, insertion of it at the placentalmargin produces a battledore placenta and

its attachment to the fetal membranes is avelamentous insertion of the cord.



If insertion of cord

at the placental

margin-- battledore placenta

►Velamentous placenta



Velamentous insertion of umbilical cord

Velamentous placenta :• is a placenta in

which the umbilical

blood vesselsabnormally travel

through the

amniochorionic

membrane before

reaching the

placenta proper.



• If these blood vessels cross the internalos, a serious condition called vasa previa

exists.

• In vasa previa, if one of the umbilical blood

vessels ruptures during pregnancy, labor,

or during delivery, the fetus will bleed todeath.



►Blood vessels may be lodged between the fetus

and the entrance to the birth canal.

►The unprotected vessels may rupture at any time

during pregnancy, causing fetal hemorrhage and

death.

Circumvallate placenta



• Is a placenta with a dense ring around the periphery

produced by excessive growth of the surrounding tissueof the uterus.

• Circumvallate placenta is thought to result from deepimplantation of the placenta into the decidua. Because of

this excessive implantation, the placenta covers morethan half of the fetal sac.

• The placenta reduces this excessive covering to thenormal one-fourth(15-30%=1/6th-1/4th) by separating from

the uterine wall, with the resultant back folding of theplacenta and fetal membranes towards the chorionicsurface.



Circumvallate placenta :

is a placenta with a

dense ring around

the peripheryproduced by

excessive growth of

the surrounding

tissue of theuterus.



►Circumvallate placenta is thought to result from deepimplantation of the placenta into the decidua.

►Because of this excessive implantation, the placenta coversmore than half of the fetal sac. The placenta reduces this

excessive covering to the normal one-fourth by separating

from the uterine wall, with the resultant back folding of the

placenta and fetal membranes towards the chorionic surface.



Complications : are rare but may cause

• Bleeding (usually painless)

• Severe intermittent uterine contractions

Placenta previa



• occurs when the placenta attaches in the lower partof the uterus, covering the internal os.

►The placenta normally implants in the posteriorsuperior wall of the uterus.

• Because the placenta blocks the cervical opening,delivery is usually accomplished by cesareansection.

• This condition is clinically associated with repeatedepisodes of bright red vaginal bleeding.



►Uterine (maternal) blood vessels rupture during the later part

of pregnancy as the uterus gradually dilates.

►The mother may bleed to death, and the fetus will also beplaced in jeopardy because of the compromised blood supply.

►Because the placenta blocks the cervical opening, delivery is

usually accomplished by cesarean section.



Placental abruption



• occurs when a

normally implantedplacenta prematurelyseparates from the

uterus before deliveryof the fetus.

• It is associated withmaternal hypertension.



Symptoms:Placental abruption can begin anytime after 20 weeks of pregnancy.

Classic signs and symptoms of placental abruption include:

• Vaginal bleeding

• Abdominal pain

• Back pain

• Uterine tenderness

• Rapid uterine contractions, often coming one right after another

► Abdominal pain and back pain often begin suddenly. The amount of vaginal bleeding canvary greatly, and doesn't necessarily correspond to how much of the placenta hasseparated from the inner wall of the uterus. It's even possible to have a severe placentalabruption and no visible bleeding.



►if left untreated, placental abruption puts both mother and

child in jeopardy.

►Placental abruption is an emergency, requiring immediate

medical attention.



Placental accreta



• an abnormally deepattachment of the

placenta, through the

endometrium and into

the myometrium.



• There are three forms of placenta accreta,

distinguishable by the depth of penetration.

• occurs when there is abnormal adherence of thechorionic villi to the uterine wall with partial or

complete absence of the decidua basalis.

• The most common form of placenta accreta is aninvasion of the myometrium which does not penetrate

the entire thickness of the muscle. This form of thecondition accounts for around 75-78% of all cases,and has no name other than placenta accreta.



There are two further variants of the condition:

• Placenta increta occurs when the placenta further extends into the myometrium and happens inaround 17% of all cases.

• Placenta percreta, the worst form of the conditionand occurring in 5-7% of cases, is when theplacenta penetrates the entire myometrium to the

uterine serosa (invades through entire uterinewall).

• This variant can lead to the placenta attaching toother organs such as the rectum or bladder .



►Causes of placenta accreta:• The specific cause of placenta accreta is unknown, but related to

placenta previa and previous cesarean deliveries.

►Diagnosis• Ultrasound

►Treatment• Unfortunately there is nothing which can be done to prevent it and

there is little that can be done for treatment once placenta accreta hasbeen diagnosed.If placenta accreta has been diagnosed- monitor pregnancy withthe intent of scheduling a delivery and surgery (CS), sometime

requires hysterectomy.

►Complication:• premature delivery

• bleeding during the third trimester



Succenturiate placenta



• is a placenta consisting of small accessorylobes completely separate from the main

placenta.

• Care must be taken to assure that theaccessory lobes are eliminated in the

afterbirth.



►►Care must be taken to assure that the accessory lobes

are eliminated in the afterbirth.



Blood circulation : Adult



Circulatory System of the Fetus



Fetal circulation involves three shunts: O2-DO2

• Ductus venosus

• Ductus arteriosus, and

• Foramen ovale



• A. Highly oxygenated and nutrient-enriched bloodreturns to the fetus from the placenta via the leftumbilical vein. (Note: Highly oxygenated blood iscarried by the left umbilical vein, not by an artery asin the adult.)

• Some blood percolates through the hepatic

sinusoids; most of the blood bypasses thesinusoids by passing through the ductus venosus and enters the inferior vena cava (IVC).



• From the IVC, blood enters the right atrium,where most of the blood bypasses the rightventricle through the foramen ovale to

enter the left atrium.

• From the left atrium, blood enters the leftventricle and is delivered to fetal tissues via

the aorta.



B. Poorly oxygenated and nutrient-poor fetal

blood is sent back to the placenta via rightand left umbilical arteries.

• C. Some blood in the right atrium enters the

right ventricle.

• Blood in the right ventricle enters the

pulmonary trunk, but most of the bloodbypasses the lungs through the ductus

arteriosus.



• Fetal lungs receive only a minimal amount of blood for growth and development; the blood

is returned to the left ventricle via pulmonary

veins.

• Fetal lungs are not capable of performing

their adult respiratory function because they

are functionally immature and the fetus is

underwater (amniotic fluid). The placenta

provides respiratory function.



Amnion



• The amnion is a membrane building theamniotic sac that surrounds and protects anembryo.

• The thin but tough amnion forms a fluid-filled,membranous amniotic sac that surrounds theembryo and fetus.

• The primary function of this is the protectionof the embryo for its development.



intraentbryortic mesoderm

Amniotic Fluid



• Amniotic fluid plays amajor role in fetal growthand development.

• It is derived from thematernal tissue bydiffusion across the

amniochorionic membranefrom decidua perietalis.



• Before keratinization of skin occurs, thea major pathway for passage of water and

solutes in tissue fluid from the fetus to the

amniotic cavity is through the skin.

• Thus, amniotic fluid is similar to fetal tissue fluid.



• Beginning in the eleventh week, the fetuscontributes to the amniotic fluid by excreting urine into the amniotic cavity.

• By late pregnancy about a half-liter of urine isadded daily

• The volume of amniotic fluid normally increasesslowly, reaching about 30 ml at 10 weeks, 350 ml at20 weeks, and 700 to 1000 ml by 37 weeks.



• The water content of amniotic fluidchanges every 3 hours

• Amniotic fluid is swallowed by the fetusand absorbed by the fetus's respiratory

and digestive tracts.

Significance of Amniotic Fluid



• Permits symmetrical external growth of theembryo and fetus.

• Acts as a barrier to infection.

• Prevents adherence of the amnion to the embryo

and fetus.

• Cushions the embryo and fetus against injuries by

distributing impacts the mother receives.



• Helps control the embryo's body temperatureby maintaining a relatively constanttemperature.

• Enables the fetus to move freely, therebyaiding muscular development in the limbs.

• Is involved in maintaining homeostasis of fluid and electrolytes.

Composition of amniotic fluid



• About 99% of the fluid in the amniotic cavityis water.

• Remaining 1% is desquamated fetal epithelialcells, organic and inorganic salts.

• Half the organic constituents are protein

(alpha-fetoprotein); the other half consists of carbohydrates, fats, enzymes, hormones, andpigments.



• As pregnancy advances, the composition of theamniotic fluid changes as fetal excreta ( meconium

[fetal feces] and urine) are added.

• Because fetal urine enters the amniotic fluid,

studies of fetal enzyme systems, amino acids,

hormones, and other substances can be conducted

on fluid removed by amniocentesis.



• Studies of cells in the amniotic fluid permit

diagnosis of the sex of the fetus and detection of fetuses with chromosomal abnormalities such as intrisomy 21, the Down syndrome

• High levels of alpha-fetoprotein (AFP) in the amnioticfluid usually indicate the presence of a severeneural tube defect (e.g., anencephaly)

• Low levels of AFP may indicate chromosomalaberrations such as trisomy 21.

Amniotic fluid volume

• Diagnosis is made by ultrasound measurement of the



g yamniotic fluid index.

• Amniotic fluid index (AFI) is a rough estimate of theamount of amniotic fluid and is an index for the fetalwellbeing.

• AFI is the score given to the amount of amniotic fluidseen on pregnant uterus by ultrasound.

• An AFI between 8-18 is considered normal.

• An AFI < 5-6 is considered as Oligohydramnios

• An AFI > 20-24 is considered as Polyhydramnios



Disorders of Amniotic fluid volume



Oligohydramnios: deficiency of amniotic fluid.

Polyhydroamnios : an excess of amniotic fluid.



Oligohydramnios : is a condition in pregnancycharacterized by a deficiency of amniotic fluid.

►It is typically caused by fetal urinary tract

abnormalities such as• Bilateral renal agenesis

• Fetal polycystic kidneys or

• Genitourinary obstruction• Uteroplacental insufficiency.



• Bilateral renal agenesis is the uncommonand serious failure of both a fetus' kidneys

to develop during gestation.

• The absence of kidney results in the

absence of amniotic fluid after 12-13

weeks. Therefore, oligohydramnios

causes the pulmonary hypoplasia (an

incomplete development of the lungs) .



• Polycystic Kidney Disease (PKD) is a hereditary

disorder that causes fluid-filled cysts to formin the kidneys.

• Damage to the kidneys is caused by theenlarging cysts.



Complications of oligohydramnios• Fetal abnormalities like pulmonary

hypoplasia

• Facial and limb defects due to fetal

compression by the uterine wall• Compression of umbilical cord is also a

serious complication.



• Polyhydramnios (polyhydramnion,hydramnios) : an excess of amniotic fluid in theamniotic sac.

• It is seen in 0.5 to 5% of pregnancies.

• It is typically diagnosed when the amniotic fluidexceeds 2500 mL (normal= 700 to 1000 ml)

• The opposite to polyhydramnios isoligohydramnios, a deficiency in amniotic fluid.



• About 20% of cases are due to maternal diabetesmellitus, which causes fetal hyperglycemia andresulting polyuria (fetal urine is a major source of

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amniotic fluid).

• About another 20% of cases are associated with fetalanomalies that impair the ability of the fetus to swallow(the fetus normally swallows the amniotic fluid). Theseanomalies include :

• Gastrointestinal abnormalities such as esophagealatresia, duodenal atresia, and tracheoesophagealfistula .

• chromosomal abnormalities such as Down's syndromeand Edwards syndrome (which is itself often associatedwith GI abnormalities)



• Neurological abnormalities such as anencephaly(which impair the swallowing reflex)

• Twin pregnancy

• It can also be caused by some systemic medicalconditions in the mother, including cardiac or kidney problems.

• However, it should be reported that in 60-65%cases of polyhydramnios, the causes areunknown .



Elevated AFP levels are associated with



• Neural tube defects (e.g., spina bifida or anencephaly)

• Omphalocele

• Esophageal and duodenal atresia (which

interfere with fetal swallowing).

Reduced AFP levels are associated with

• Down syndrome.



Spina bifida is a neural tube defect caused by the

failure of the fetus's spine to close properly during the

first month of pregnancy (incomplete closure of the

NT)

►The most common location of the malformations is

the lumbar and sacral areas.



Anencephaly is a cephalic disorder that results from a neural

tube defect that occurs when the cephalic (head) end of theneural tube fails to close, usually between the 23rd and 26th

day of pregnancy, resulting in the absence of a major portion

of the brain, skull, and scalp.



Omphalocele : Type of abdominal wall defect in which theintestines, liver, and other organs remain outside of theabdomen in a sac because of a defect in the development of the muscles of the abdominal wall.

Amniocentesis

• Amniocentesis (also referred to as amniotic fluidtest or AFT) is a medical procedure used in



test or AFT), is a medical procedure used in

prenatal diagnosis of chromosomal and fetalabnormalities, in which a small amount of amnioticfluid, which contains fetal tissues, is extracted fromthe amnion or amniotic sac and the fetal DNA isexamined for genetic abnormalities.

• Amniocentesis is most safely performed after the14th-18th week of pregnancy.

Complications :

• Injury/trauma to the fetus

• Infection of the amniotic sac from the needle

• Serious complications can result in miscarriage



AFP = 0.8 to 2.3 (normal)If <0.8 -------------------------- DSIf >2.8 --------------------------- NTD



Disturbance in Neurulation may result in severe abnormalities of brain andspinal cord-----NTD



In case of Down syndrome

▪Low AFP (<0.8)

▪High HCG

▪High estriol

These are known as triple markers for Trisomy 21.



• Changes of uterus during pregnancy• Parturition



20 weeks

Parturition



• Parturition is the process during which thefetus, placenta, and fetal membranes are

expelled from the mother's reproductive tract.

• Labor is the sequence of involuntary uterine

contractions that result in dilation of the uterine

cervix and expulsion of the fetus andplacenta from the uterus.



• Dilatation : 20-14 hrs – The first stage of labor begins when regular

painful contractions of the uterus occur less

than 10 minutes apart.

– The first stage of labor ends with complete

dilation of the cervix and is the most time

consuming stage of labor.



• Expulsion: 1-2 hrs – The second stage of labor, begins when the

cervix is fully dilated and ends with delivery of

the baby.

– As soon as the fetus is outside the mother, it

is called a newborn infant or neonate



• The placental stage: 30 mins – The third stage of labor, begins as soon as the

neonate is born and ends when the placenta and

membranes are expelled.

– Retraction of the uterus and manual compression

of the abdomen reduce the area of placental

attachment.



Stage2: delivery of the newborn



• Recovery: 1-2 hrs – The fourth stage of labor, begins as soon as theplacenta and fetal membranes are expelled

– This stage lasts about 2 hours

– The myometrial contractions constrict the spiralarteries that supplied blood to the intervillous space

– These contractions prevent excessive uterinebleeding.



Multiple Pregnancies

Multiple Pregnancies



• A multiple birth occurs when more than onefetus is carried to term in a single pregnancy.

• Different names for multiple births are used,depending on the number of offspring.

• Common multiples are two and three, knownas twins and triplets.



Terminology

►Terms used for the order of multiple births are largelyderived from the Latin names for numbers



derived from the Latin names for numbers.

►Two offspring (twins) is the most common form,

nine (nonuplets) or more being the rarest.

• Two offspring – twins

• Three offspring – triplets• Four offspring – quadruplets

• Five offspring – quintuplets

• Six offspring – sextuplets

• Seven offspring – septuplets• Eight offspring – octuplets

• Nine offspring – nonuplets

Causes and frequency

• In general, twins occur naturally at approximately



g , y pp y

the rate of 1/89 births.

• However, for reasons that are not yet known, theolder a woman is the more likely she is to have a

multiple birth naturally.

• It is thought that this is due to the higher level of follicle-stimulating hormone that older women

sometimes have as their ovaries respond moresluggishly to FSH stimulation.



Certain factors appear to increase the likelihood



Certain factors appear to increase the likelihoodthat a woman will naturally conceive multiples.These include:

• mother's age — women over 35 are more likelyto have multiples than younger women.

• mother's use of fertility drugs — approximately35% of pregnancies arising through the use of fertility treatments such as IVF involve more than

one child.



Risks of multiple pregnancies : • Premature birth and low birth weight

• Cerebral palsy: is more common among multiple births thansingle births.



single births.

►CP refers to any one of a number of neurological disordersthat appear in infancy or early childhood and permanentlyaffect body movement and muscle coordination.

• Incomplete separation of embryo : Multiples may becomemonochorionic, sharing the same chorion, with resultant riskof twin-to-twin transfusion syndrome.

• Mortality rate (stillbirth): Multiples are also known to have ahigher mortality rate. It is more common for multiple births tobe stillborn (when fetal death occurs after 20 weeks of pregnancy).



Twin transfusion syndrome characterized by arteriovenousshunt at a shared placental cotyledon in diamniotic

monochorionic twins.



• It has been observed that if the firstbornare twins, a repetition of twinning or some

other form of multiple birth is about fivetimes more likely to occur at the next

pregnancy than in the general population.



• Hence these twins are no more genetically



Hence, these twins are no more geneticallyalike than siblings born at different times.

• Dizygotic twins have two placentas, two

amniotic sacs, and two chorions (i.e., adiamnionic-dichorionic membrane).

• Development of DZ twins



Development of DZ twins

– Show hereditary tendency

– May be of same or different sex

– DZ twins always have two amnions and two

chorions, but the chorions and placentas may

be fused

– Genetically not alike

http://upload.wikimedia.org/wikipedia/commons/a/a9/Being_a_twin_means_you_always_have_a_pillow_or_blanket_handy.jpg



Fraternal twin sisters taking a nap. Twins, the most common

kind of multiple birth among humans, occur in about 1 out of

every 80 pregnancies.

Monozygotic (identical) twins

• Monozygotic twins result from the

http://upload.wikimedia.org/wikipedia/commons/a/a9/Being_a_twin_means_you_always_have_a_pillow_or_blanket_handy.jpg



yg

fertilization of one secondary oocyte by one

sperm.

• The resulting zygote forms a blastocyst in

which the inner cell mass (embryoblast) splitsinto two.

• Hence, these twins are genetically identical.

– Genetically and physically alike

– Same sex



– In 65% of cases, monozygotic (identical) twins have one



, yg ( )

placenta, two amniotic sacs, and one chorion (i.e., a

diamnionic monochorionic membrane).

– Uncommonly, MZ twins with two amnions, two chorions,

and two placentas that may or may not fuse can occur

– So it is impossible to determine from the membranesalone whether the twins are MZ or DZ.



Conjoined (Siamese) twins

• Conjoined twins form exactly like



monozygotic twins except that the inner cellmass (embryoblast) does not completely split.

• Hence, two embryos form, but they are joinedby tissue bridges at various regions of the

body (e.g., head, thorax, or pelvis).



Other Types of Multiple Birth



• Triplets may be derived from: – one zygote and be identical

– Two zygotes and consist of identical twins

and a singleton (a set with exactly one element)

– Three zygotes and be of the same sex or of

different sexes.



Identical triplets like these three sisters occur when a singlefertilized egg splits in two and then one of the resulting two

eggs splits again.

Superfecundation • Fertilization of two or more oocytes at different times.



• Superfecundation is the fertilization of two or moreova from the same cycle by sperm from separateacts of sexual intercourse.

• The term is also sometimes used to refer to theinstances of two different males fathering fraternaltwins, though this is more accurately known asheteropaternal superfecundation.

• DZ human twins with different fathers have beenconfirmed by genetic markers.



Superfecundation is the fertilization of two or more ova fromthe same cycle by sperm from separate acts of sexualintercourse.

• Superfecundation most commonly happens within hoursor days of the first instance of fertilization with ovareleased during the same cycle.

• There is a small time window when eggs are able to be



fertilized. Sperm cells can live inside a woman’s body for 4 –5 days. Once ovulation occurs, the egg remains viablefor 12 –48 hours before it begins to disintegrate. Thus, thefertile period can span 5 –7 days.

• Ovulation is usually suspended during pregnancy toprevent further ova becoming fertilized and to helpincrease the chances of a full term pregnancy. However, if an ovum is released after the female was alreadyimpregnated when previously ovulating, there is a

chance of a second pregnancy—albeit at a different stageof development. This is known as superfetation.

Preeclampsia and eclampsia

P l i i h dd d l f



• Preeclampsia is the sudden development of maternal hypertension (>160/110 mm Hg), edema (hands and/or face), and proteinuria (>5 g/24 hr)usually after week 32 of gestation (thirdtrimester).

• Eclampsia includes the additional symptom of convulsions.



• The pathophysiology of preeclampsia involvesa generalized arteriolar constriction that impactsthe brain (seizures and stroke), kidneys (oliguriaand renal failure), liver (edema), and small bloodvessels.

Ri k f i l d



Risk factors includeNulliparity

Diabetes

Hypertension

renal disease

twin gestation

Treatment of severe preeclanapsia involvesmagnesium sulfate (for seizure prophylaxis)and hydralazine (blood pressure control).

• once the patient is stabilized, delivery of the fetusshould ensue immediately.



Prenatal Diagnostic Procedures

• Prenatal diagnosis is indicated in about 8% of all

i P t l di ti d i l d th



pregnancies. Prenatal diagnostic procedures include thefollowing:

1. Ultrasonography : is commonly used to date apregnancy, to diagnose a multiple pregnancy, toassess fetal growth, to determine placenta location,to determine the position and lie of the fetus, todetect certain congenital anomalies, and to monitor needle or catheter insertion during amniocentesisand chorionic villus biopsy.

• Optimal gestational stage for identification of fetalanatomic structural anomalies is 18 to 20 weeks.



2. Amniocentesis : is a transabdominal sampling of

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amniotic fluid and fetal cells. Amniocentesis is performed at weeks 14-18 and is indicated

in the following situations:

• the woman is over 35 years of age

• a previous child has a chromosomal anomaly

• one parent is a known carrier of a translocation or inversion

• one or both parents are known carriers of an X-linked

recessive or • autosomal recessive trait; or

• there is a history of neural tube defects.

The sample obtained is used in the following studies:

Al h F i i d di l b d f



• Alpha -Fetoprotein assay is used to diagnose neural tube defects.

• Spectrophotometric assay of bilirubin is used to diagnosehemolytic disease of the neworn (i.e., erythroblastosis fetalis) dueto Rh-incompatibility.

• Lecithin-sphingomyelin (L/S) ratio and phosphatidylglycerol assay are used to determine lung maturity of the fetus.

• DNA analysis: A wide variety of DNA methodologies are available

(e.g., karyotype analysis, Southern blotting, and RFLP analysis[restriction fragment length polymorphism]) to diagnosechromosomal abnormalities and single-gene defects.

3. Chorionic villus biopsy : is a transabdominal

t i l li f th h i i illi



or transcervical sampling of the chorionic villito obtain a large amount of fetal cells for DNA

analysis.

Chorionic villus biopsy is performed at weeks

6-11 (i.e., much earlier than amniocentesis),

thereby providing an early source of fetal

cells for DNA analysis.



4 Percutaneous umbilical blood sampling



4. Percutaneous umbilical blood sampling(PUBS) is a sampling of fetal blood from

the umbilical cord (from umbilical vein).

• It is performed after 20 weeks for fetal

karyotyping, IgM antibody detection, blood

typing and intrauterine BT.

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