Placenta

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Placenta
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Placenta Development

• Placenta
• Serves to protect the embryo as well as provide
  nutrition, respiration, and excretion
• Responsible for metabolism transfer of
  nutrients, wastes, antibodies, hormones
• Drugs infections can cross placenta

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Placenta Development

• Develops from fetal chorion maternal
  endometrium
• Visualized at 8 to 10 weeks as a focal
  homogeneous hyperechoic thickening
• Fetal surface of placenta is smooth umbilical
  cord is attached near center

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Developing Placenta
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Developing Placenta
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Placenta Hormone Production

• Human Chorionic gonaditrophin (HCG)
• Prolactin
• Estrogen
• Progesterone

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Evaluate the Placenta

• Reasons why we look at placenta
• R/O placenta previa
• R/O placenta abruption
• Localization prior to amniocentesis
• Placental aging
• Localization for CVS

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Maternal Circulation

• The maternal (irregular lobular surface) surface
  of the placenta (basilar plate - decidua basalis)
  is divided into cotyledons, which can be thought
  of as divisions of the placenta
• Cotyledons - 10-38 functional lobes composed of
  maternal sinusoids and chorionic villous
  structures.
• These cotyledons are formed by growth of septa
  from the maternal endometrium into the placenta.

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Maternal Circulation

• Each cotyledon contains maternal arterioles which
  supply a pool of oxygenated blood into the
  intervillous space which is found within the
  placental lobules.
• This intervillus space is formed by the villi
  projections of the trophoblastic cells. These
  trophoblastic cells serve as the fetal
  capillaries.

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Maternal Circulation

• Both maternal and fetal Blood flows over the
  chorionic villi in the intervillous spaces. This
  allows for exchange of oxygen nutrients.
• This is the site of fetal-maternal exchange
• These fetal capillaries join into one fetal vein,
  the umbilical vein, which feeds oxygenated blood
  to the fetus.
• After the blood circulates through the fetus the
  deoxygenated blood exits the fetus via the two
  umbilical arteries.

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Maternal Circulation

• The two umbilical arteries break down into much
  smaller arteries in the placenta where the blood
  becomes oxygenated again.
• Maternal blood reenters the maternal circulation
  via basilar, subchorionic, interlobar, and
  marginal veins (all which are maternal veins).
• The rate of uteroplacental flow increase from 50
  cc/min. at 10 wks to 500-600 cc/min. at term.

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Maternal Circulation Review

• Maternal Circulation
• Placenta
• Cotyledons
• Maternal arterioles
• Pool of oxygenated blood
• Intervillous space
• Fetal capillaries
• Fetal vein

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Placenta Vascularity
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Placenta Vascularity
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Fetal Circulation

• Oxygenated blood from the single umbilical vein
  enters the fetal portal system through the
  umbilical portion of the left portal vein.
• From the left portal vein the blood has two
  routes it can go through
• Blood can go through the fetal liver and enter
  the IVC through the hepatic veins
• Or the blood can pass through the ductus venosus,
  which bypasses the liver circulation and enters
  the hepatic veins draining into the IVC.

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Fetal Circulation

• The blood then goes from the left hepatic vein to
  the IVC into the right atrium.
• A small portion of blood from the right atrium
  goes to the right ventricle to the lungs via the
  pulmonary arteries.
• But even most of this blood is shunted away from
  the lungs and goes into the ductus arteriosus
  that shunts blood directly into the descending
  aorta for systemic circulation
• After birth the ductus arteriosus constricts and
  permanently closes becoming the ligamentum
  arteriosum
• , however, the majority of the blood is shunted
  to the left atrium via the Foreman of ovali

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Fetal Circulation

• The majority of blood in the right atrium goes to
  the left atrium via the foreman ovali, which is a
  hole between the right and left atrium.
• The blood now goes from the left atrium to the
  left ventricle to the aorta
• Most of the blood then returns to the placenta
  via two umbilical arteries this is deoxygenated
  blood.
• Some blood does remain to circulate within the
  fetus

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Review of Fetal Circulation

• 1. Umbilical vein (oxygenated blood)
• 2. Umbilical portion of hepatic portal
• 3. Left portal
• 4. Ductus venous
• 5. Left hepatic vein
• 6. IVC (Rt. Atrium, Lung's, Rt. Ventricle,
  

• 7. Foramen ovali
• 8. Lt. atrium 9. Lt. ventricle
• 10. Aorta
• 11. Two umbilical arteries

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Fetal Circulation
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Placenta

• A placenta is graded according to the following
• The amount and pattern of echogenic densities
  within the placenta
• The changes in the chorionic plate
• Chorion Plate This is the fetal surface- the
  interface between the amniotic fluid the
  placenta

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Placenta (image)
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Placenta

• Calcific deposits can occur in the substance of
  the placenta throughout pregnancy
• There is an increased incidence of placental
  calcification with lower parity and higher
  gestational age
• Calcific deposits generally occur along the septa
  and in the basalar plate

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Grade 0 Placenta (Diaphragm)
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Grade 0 Placenta

• Grade 0
• The chorionic plate is smooth, straight, and well
  defined
• The placenta has a homogeneous texture
• There are no focal densities seen in the basal
  layer
• Grade 0 placentas are usually seen in the first
  and second trimester, prior to 28 weeks

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Grade 0 Placenta
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Grade 0 Placenta
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Grade 0 Placenta
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Grade 0 Placenta
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Grade 1 (Diaphragm)
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Grade I Placenta

• Characteristic undulations (indentation) of the
  chorionic plate
• Spotlike densities dispersed through out the
  placental tissue (calcium deposits)
• The basal layer is regular
• A Grade I placenta may appear as early as 14
  weeks, but it is most commonly seen between 30-34
  weeks and may persist until term

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Placenta Grade 1
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Placenta Grading (Grade l)
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Grade I Placenta

• Few scattered calcifications

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Grade II (Diaphragm)
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Grade II Placenta

• Chorionic plate develops more marked indentations
• The placental substance is incompletely divided
  by linear or comma shaped echogenic densities
• Increase in the echogenic densities in the
  placental substance
• The basal layer also contains linear echogenic
  densities
• Indentations extending into the placenta but not
  to the basal layer
• Does not usually appear until after 30 weeks

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Grade II Placenta (undulations)
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Placental Clacifications (Grade II Placenta)
Calcifications are seen in aging placentas
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Grade II Placenta
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Grade III Placenta (Diaphragm)
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Grade III Placenta

• The chorionic plate appears interrupted by
  echogenic indentations that extend to basal layer
• The placental substance is divided by these septa
  and may contain anechoic or hypoechoic regions
• Irregular echogenic areas throughout placenta
• Usually not seen until 35 weeks
• Found in 30 of term placentas

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Grade III Placenta

• Echogenic foci along the basilar plate are more
  prominent
• Basal stripling - linear arrangement of echogenic
  calcifications along the basilar plate, usually
  not seen prior to 34 wks
• Can be seen in the third trimester near term
• Prominent calcifications scattered throughout the
  placenta and along the basalar plate

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Grade III Placenta Cotelydons
                                                
 ltgt
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Grade III Placenta Cotelydons
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Grade III Placenta Cotelydons
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Placenta Grading Review (Grade 0-I)

• Grade 0
• No calcifications are seen, usually seen prior to
  28 weeks
• Grade 1
• Scattered calcifications are seen
• (Usually seen between 30-34 weeks)
• Can be seen prior to this and not be considered
  abnormal

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Placenta Grading Review (Grade II-III)

• Grade II
• Basal calcifications are seen
• 45 of placentas go to grade II
• More commonly seen over 30wks
• Grade III
• Basal and interlobar septal calcifications are
  seen
• Found in 30 of term placentas
• Not usually seen prior to 35 wks

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Reasons the Placenta Ages to Quickly

• Hypertension - most common
• Smoking
• Sickle cell anemia
• Drug abuse

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Reasons for Delayed Placenta Aging

• Rh sensitization
• Maternal diabetes
• Twins

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Placenta Thickness

• 4-5 cm is a normal placental thickness.
• The placenta increases in thickness until 33
  weeks of gestation, after that its thickness
  gradually decreases
• Anything greater than 6-7 cm or less than 4 cm is
  abnormal
• A mature placenta weighs 500 - 600 grams and is
  16-20 cm in length

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Reasons for a Thickened Placenta

• RH sensitization
• Maternal intrauterine infections
• Maternal diabetes
• Maternal anemia
• Feto-maternal hemorrhage
• Non-immune hydrops
• Chromosomal abnormalities
• Uterine contraction

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Reasons for a Thin Placenta

• Preeclampsia
• Placental infarction
• Intrauterine infections
• Chromosomal abnormalities
• As a general rule of thumb, after 23 weeks the
  placenta should be no thinner than 1.5 cm or no
  thicker than 5.0 cm

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Placenta

• Myometrium
• The muscle that forms the wall of the uterus.
• A contraction in the myometrium of the placenta
  can cause it to appear thick or bulbous

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Placenta

• Erythroblastosis fetalis
• A form of fetal anemia in which the fetal red
  cells are destroyed by contact with a maternal
  antibody that is produced by the mother in
  response to a previous pregnancy
• Severe fetal heart failure results

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Placental Position

• Usually the placenta location is mid to fundal in
  the uterus which reflects the site of
  implantation.
• Placenta positions
• 1. Posterior
• 2. Anterior
• 3. Lateral-right or left
• 4. Fundal
• 5. Combination

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Placenta Positions

• Ultrasound Findings
• An over distended bladder focal uterine
  contractions are the two most common technical
  factors responsible for a false-positive
  diagnosis by ultrasound

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Placenta Migration

• The placenta is seen as a definite structure by
  10-12 weeks and reaches its final location by 4
  months
• This term is used to describe the apparent shift
  in the placental position early in pregnancy
  prior to 16wks.
• The placenta appears to be move from the cervical
  to the fundal portion of the uterus.

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Demonstrating the Lower Uterine Segment (LUS)

• 1. Demonstrate with a full bladder to R/O
• a. placenta previa
• b. complete previa
• If the placenta extends into the LUS, empty the
  bladder because there may be a placenta previa.
• Only with an empty bladder can you be sure the
  cervix isn't falsely being lengthened by the
  bladder being over distended. (Sagittal)

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LUS

• Show that the placenta lies to one side of the
  cervix. (Transverse)
• It may be hard to demonstrate with a cephalic
  presentation.

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LUS
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Translabial
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Translabial ultrasound
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TRANSLABIAL
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TRANSLABIAL
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Transvaginal