IN THE NAME OF GOD

PLACENTA DR.E. ZAREAN

Zygote

Pregnancy: Level 1 Fertilisation Cell division Next slide

First week

Fertilisation Cell division Wafted along Fallopean tube into uterus (or Oviduct)

Cleavage and blastocyst formation: This cleavage starts within 24 hours of fertilization and occurs nearly every 12 hours repeatedly The resultant 16 cells mass is called morula which reaches the uterine cavity after about 4 days from fertilization.

Cleavage and blastocyst formation: A cavity appears within the morula converting it into a cystic structure called blastocyst. The cells become arranged into an : Inner mass (embryoblast) which will form all the tissues of the embryo, and an Outer layer called trophoblast which invade the uterine wall.

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).

blastocyst Endometrium Next slide

Wafted along Fallopean tube Implantation in uterine wall Fertilisation Cell division Wafted along Fallopean tube Implantation in uterine wall Secretory duct Capillary Endometrium Trophoblast Uterine epithelium Embryo Yolk sack Blastocoel Blastocyst Next slide

Placenta formation Lacunae form within synctiotrophoblast--maternal blood fills these spaces Vili form with embryonic capillaries down middle

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.

After implantation, the trophoblast differentiates into 2 layers: Chorion: After implantation, the trophoblast differentiates 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.

Chorion: 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: 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.

Primary villous Secondary villous

Transverse section of tertiary villous

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.

Functions of the placenta Fertilisation Cell division Wafted along Fallopean tube Implantation in uterine wall Formation of placenta Functions of the 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 Next slide

Hormonal control of pregnancy Phase 1 Corpus luteum Oestrogen and progesterone Stimulated by luteinising hormone (LH) from pituitary Next slide

Hormonal control of pregnancy Phase 2 Trophoblast and early placenta Produces human chorionic gonadotrophin (hCG) This has LH like effects on corpus luteum hCG is a peptide hormone Basis 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 Next slide

Hormonal control of pregnancy Phase 3 The placenta becomes the dominant source of oestrogen and progesterone Also secretes human chorionic gonadotrophin human placental lactogen Next slide

Blood levels of hormones during gestation, 40 weeks Progesterone hCG Oestrogen hPL Blood concentration Next slide End lastperiod Parturition

Progesterone hCG Oestrogen hPL Blood concentration 0 10 20 weeks 30 40

Next slide

Placenta formation Villi bathed in maternal blood in lacunae--exchange of nutrients, O2, CO2 After 13 weeks, full placenta--pancake-shaped organ.

Placental Abnormalities Abnormalities of the Membranes Umbilical cord Abnormalities

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

Clinical significance 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

Clinical significance Abnormality Definition Clinical significance 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

Clinical significance 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

Clinical significance Abnormality Definition Clinical significance 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

Placental Abnormalities Placental calcification

Placental Abnormalities -Tumors of the Placenta- Gestational Trophoblastic Disease Chorioangioma(Hemangioma) Tumors Metastatic to the Placenta Embolic Fetal Brain Tissue

Placental Abnormalities -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

Chorioangioma (Hemangioma)

Abnormalities of the Membranes Meconium Staining Chorioamnionitis Other Abnormalities

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 .

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 .

Abnormalities of the Membranes - Meconium Staining - 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 23

Abnormalities of the Membranes - Meconium Staining - 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

Abnormalities of the Membranes -Other 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

Umbilical Cord Abnormalities Length : appreciable variation, extremes range - no cord(achordia) ~ lengths<300cm - mean length : 37cm - excessively long cords : ≥ 70cm ( ≥2 SD )

Umbilical Cord Abnormalities 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

Umbilical Cord Abnormalities 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

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

Umbilical Cord Abnormalities Abnormalities of Cord insertion : usually inserted at or near the center of the fetal surface of the placenta Furcate insertion Marginal insertion Velamentous insertion Vasa Previa

Umbilical Cord Abnormalities Anomalities 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

Umbilical Cord Abnormalities Abnormalities of Cord insertion 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

Umbilical Cord Abnormalities Abnormalities of Cord insertion 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%

Umbilical Cord Abnormalities Abnormalities of Cord insertion 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%

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)

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%

Umbilical Cord Abnormalities Torsion and Strictures 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

Placental Abnormalities - Abnormal Shape or Implantation- Circumvallate(left) and cricummarginate(right) variaties of extrachorial placentas

Placental Abnormalities - Abnormal Shape or Implantation- Anomaly of Placental site

Velamentous Insertion

Vasa previa Internal cx os