Transcript PREGNANT FEMALE 3rd Trimester

PREGNANCY
rd
3
Trimester
PREGNANCY 3rd Trimester
I. Uterine Changes
A. Uterus experiences greatest period of
growth
B. Reaches into epigastric region by 8th
month
C. Endometrium
1. Layer thickens
2. Glands enlarge, may penetrate
myometrium
PREGNANCY 3rd Trimester, con’t…

Location of uterine
fundus by
developmental week
Uterine changes, continued …
D. Myometrium: arranged into three
distinct layers
1. External layer: beneath peritoneum
a. Fibers pass transversely across
fundus
b. converge @ superior angles of
uterus
Uterine changes, continued …
c. Fibers extend onto
1. fallopian tubes
2. round ligaments
3. ovarian ligaments
2. Middle layer:
a. thickest
b. meshwork of random fibers
c. many blood vessels
Uterine changes, continued … Myometrium
3. Inner layer:
a. fibers arranged circularly
b. form cones
1. Apices surround fallopian tubes
2. Fibers form sphincters around
internal ossa of tubes
Uterine changes, continued … Myometrium
4. Smooth muscle fibers hypertrophy
a. >800% (8x) larger
b. muscle fibers undergo mitosis
1. only during pregnancy
2. Lose fibers post-partum
Uterine changes, continued …
D. Wall of uterus thins as pregnancy
progresses
E. Placental “ascension” or “migration”
1. During the last part of the 3rd trimester
2. Differential growth of lower uterine
segment
3. Artifact of development
PREGNANCY 3rd Trimester, con’t…
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Early fetal period
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Middle fetal period
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8-16 weeks
17-30 weeks
Late fetal period
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13-38 weeks
PREGNANCY 3rd Trimester, con’t…
• II. Placental
Changes
• A. Chorionic Plate
• 1. Strong interface visible
• 2. Between amniotic cavity
and fetal surface of placenta
• 3. After 12th menstrual week =
Grade 0, mature placenta
• 4. Placenta attains a diffuse
echogenic pattern
PREGNANCY 3rd Trimester, con’t…
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Normal Mature
Placenta
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Maternal side
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Fetal side
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Microscopic view
Placental Changes, con’t….
• B. Early in 3rd trimester
•
•
•
1. changes occur
2. Detectable
sonographically
3. Grade I changes:
•
30-32
3.8 cm
a. first noted @
weeks
b. Placenta is
Placental Changes, continued …
d. Chorionic plate develops “wavy”
appearance
e. Homogeneous look is lost
f. See increased glands,
calcifications
g. see more scattered echogenic
regions
Placental Changes, continued …
• 2. Grade II changes
•
a. 34-36 weeks
•
b. Chorionic plate
develops
marked
indentations
•
Placental changes, continued…
c. Comma-shaped septa extend
from chorionic plate toward
basalis
d. Placenta becomes more
echogenic
e. Placental “mottling” appears
Placental Changes, continued …
• 3. Grade III
changes: a. 38-40
weeks (3.5 cm)
•
b. Septa extend
thru placenta
•
c. To decidua
basalis
•
d. Divide
placenta into
“cotyledons”
•
e. Calcium
deposits create
Placental changes, continued …
f. May find “cysts” between chorionic
plate and placenta
g. Areas of excessive fibrin
deposition
h. placenta starts deteriorating
i. Venous lakes develop
Placental changes, continued …
C. Thickness gradually decreases
after 32 weeks
D. Growth ceases after 38 weeks
E. Changes normal for senescent placenta
1. At birth: weighs ~ 1 lb
2. Size: ~6-8” diameter
3. Surface area: ~ 16 m2
Pregnancy, 3rd Trimester, con’t…
F. Amount of amniotic fluid
1. Increases during pregnancy
2. May reach one gallon in late 3rd
trimester
PREGNANCY 3rd Trimester, con’t…
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Placental variations
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Succenturiate placenta
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Circumvallate placenta
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Battledore placenta
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Velamentous placenta
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May result in vasa
previa
PREGNANCY 3rd Trimester, con’t…
III.Fetal Structures
A. Fetal Head
1. First visualized at 5-6 weeks
2. After 12 weeks, details can be seen:
a.
b.
c.
d.
Falx cerebri
Ventricles
Thalami
Corpus callosum
Fetal Structures: Fetal head
e.
f.
g.
h.
Septum pellucidum
Lateral fissure
Midbrain
Basilar artery
i. Cerebral
hemisphere
j. cerebellum
8.0 mm
6 months
10.5 mm
9 months
PREGNANCY 3rd Trimester, con’t…
B. Fetal Thorax
• 1. Heart: evaluation
after 10-12 weeks
• a. Four chambers: “4
chambers @ 4 months”
• b. Ventricular diameter:
34-41 weeks
• c. Aorta: early on with
Doppler
Endocardial Cushion: green
Fetal Thorax, Con’t…
2. Lungs:
a. no clear
boundaries between
lungs, diaphragm, and
liver
b. unless fluid
intervenes
3. Diaphragm:
usually visible
Fetal structures, continued …
C. Abdomen
1. Stomach
a. upper left quadrant
b. by 12-15 weeks
2. Fluid in small intestine
by 2nd trimester
3. Descending colon
a. seen in late 3rd trimester
b. filled with fluid and meconium
G.I. Tract
development at
3-4 months
Fetal structures, Abdomen, cont…
4. Umbilcal vein
a. visible in area of umbilicus
b. coursing superior and
posterior to portal sinus (vein)
5. Liver:
a. in upper right quadrant
b. with hepatic & portal veins
c. largest organ by 8 weeks
Fetal structures, continued …
D. Pelvis &
retroperitoneum
1. Kidneys: seen @
15-20 weeks
2. Urinary Bladder:
a. seen @ 13-15 weeks
b. in 3rd trimester, urine-filled
6 weeks
7 weeks
9 weeks
Fetal structures, continued …
E. Other structures
1. Skeletal components
a. Axial skeleton
b. Long bones
2. Extremities
3. Genitalia by 10 weeks (+/-)
IV. FETAL CIRCULATION
A. General
1. Ovum and yolk sac provide
initial nutrients to embryo
2. Other means must develop
early on
FETAL CIRCULATION, CON’T…
3. Blood vessel and blood formation
a. begin15-16 days after
fertilization
b. in mesoderm of yolk sac,
body stalk, chorion
4. Cardiovascular system first
to develop
Fetal circulation, continued …
5. Blood flow begins end of
the third week
6. Heart beat begins about 22 days
7. REMEMBER:
a. fetus is totally dependent on outside
source for oxygen, nutrients, and
waste disposal.
b. This source is the placenta
Fetal circulation, continued …
B. Course of blood through fetal circulation
1. Always begin at placenta
2. Vessels named with respect to fetus
3. Blood leaves placenta via umbilical or
placental vein (+ O2 blood)
Fetal circulation, continued …
4. Travels in umbilical cord
a. Through umbilicus
b. Into baby’s body
5. Ascends along falciform ligament
a. To inferior surface of liver
b. Here, enters liver
Fetal Circulation
Umbilical Vein
Fetal circulation, continued …
6. At porta hepatis, umbilical vein divides:
a. Portal vein: carries blood
through liver  hepatic
veins  IVC
b. Ductus venosus: goes
directly to IVC
Fetal Circulation
Ductus
Venosus
Portal Vein
Fetal Circulation, continued …
7. Blood in IVC is –O2 blood, and is
a. mixes with +O2 blood from hepatic
veins, ductus venosus
b. is now “mixed” blood
8. IVC enters right atrium
Fetal Circulation
IVC
Fetal Circulation, continued …
a. some blood follows post-partum
path
b. Most blood is diverted
1. by valve of IVC (Eustachian
valve)
2. through foramen ovale into
left atrium
Fetal Circulation, con’t…
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Foramen Ovale
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Eustachian Valve
Fetal Circulation, continued …
9. From left atrium:
a. blood is pumped to left ventricle
b. out the aorta
c. throughout systemic circulation
Fetal Circulation, continued …
10. Blood from head and upper extremities
a. returns to right atrium via SVC
b. mixes with blood from IVC
11. Blood to lower body
a. passes from aorta common
iliac arteries
internal iliac
arteries
Fetal Circulation
SVC
IVC
Common Iliac
Arteries
Umbilical
Arteries
Fetal Circulation, continued …
12. Fetal lungs are non-functional
a. require minimal blood supply
b. shunt is present between
pulmonary artery and aorta
c. ductus arteriosus: by-passes
lungs
Fetal Circulation, con’t…
Ductus Arteriosus
Fetal Circulation, continued
13. Vessels in
umbilical cord
a. single large
vein
b. two smaller
arteries
Fetal circulation, continued …
14. Recap of fetal circulation:
a. Oxygenated blood carried by
1. umbilical vein
2. portal vein
3. ductus venosus
Fetal circulation, continued …
b. Placenta is:
1. Fetal organ of respiration,
nutrition & excretion
2. Most blood from placenta
a. goes thru liver
b. before entering IVC
Fetal circulation, continued …
c. Eustachian Valve
1. directs most blood from IVC
to left atrium
2. directs blood from SVC to right
ventricle
Fetal circulation, continued …
d. Blood from umbilical vein, IVC
1. go from L.A. to L.V. to aorta
2. then mostly to head, upper
extremities
e. Descending aorta contains mixed
blood
Fetal Circulation
Descending Aorta
Fetal circulation, con’t…
C. Changes in Cardiovascular System
at Birth
1. After pulmonary respiration begins
a. the ductus arteriosus constricts
b. blood flows to lungs
Fetal circulation, con’t…
2. More blood returns to left atrium
a. flow thru foramen ovale stops
b. Seals to become fossa ovalis
3. Ductus arteriosus
a. fills with fibrous C.T.
b. becomes ligamentum arteriosum
Fetal circulation, con’t…
4. Cutting umbilical cord causes vessels
to collapse, seal
a. Umbilical vein
b. Ductus venosus
ligamentum teres hepatis
ligamentum venosum
c. Proximal umbilical arteries
d. Distal umbilical arteries
ligaments
internal iliac arteries
lateral umbilical
Fetal Vessels: Postnatal Changes
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Ligamentum arteriosum
Fossa ovalis
Ligamentum venosum
Ligamentum teres
hepatis
Lateral umbilical
ligaments
Fetal circulation, con’t…
Patent
Urachus
D. Urachus (median
umbilical ligament)
1. Obliterated remains of allantois
2. Attaches urinary bladder to
abdominal wall
3. Can form urachal cyst (rare)
Urachal
Cyst
Fetal circulation, con’t…
3. Passes superiorly from apex of
bladder to umbilicus
4. Composed of fibrous C.T. and
smooth muscle
5. Lies between umbilical
ligaments
V. THIRD TRIMESTER BLEEDING
A. Abruptio Placentae (Placental abruption):
1. Premature separation of a normally
implanted placenta
2. May be mistaken for placenta previa
3. May be only a few mm separation
or a complete detachment
Third trimester bleeding, con’t.
4. Retroplacental bleeding occurs
5. May be external or concealed
6. Signs and symptoms vary
a. depends on degree of
separation
b. amount of blood loss
Third Trimester Bleeding, continued …
B. Placenta Previa:
1. Placenta implants over internal
os of cervix
2. Occurs in 1:200 cases
3. False positive rate of 10%
Placenta Previa
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Marginal Previa
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Partial Previa
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Complete Previa
Third Trimester Bleeding, continued …
4. Symptoms:
a. sudden painless vaginal
bleeding
b. in late third trimester
c. Followed by painless massive
bright red bleeding
Third Trimester Bleeding, continued …
5. May be mistaken for abruptio
placentae
6. Ultrasound is diagnostic modality
Third trimester bleeding, continued …
C. Rh Incompatibility: [erythroblastosis
fetalis, hemolytic disease of the newborn
(HDN)]
1. lysis of fetal RBC’s
2. due to Rh- isoimunization
3. Rh- multiparous female
4. Rh+ father and fetus
Third trimester bleeding, continued …
5. Leads to:
a. hemolysis of fetal RBC’s
b. anemia of fetus
c. congestive heart failure
d. may cause jaundice
Erythroblastosis Fetalis, continued …
3. Caused by transplacental
transmission of maternal anti-Rh
antibodies (Ab)
a. All cells contain antigens on cell
membranes, so….
b. All RBC’s contain antigens cell
membranes
Erythroblastosis Fetalis, continued …
c. ABO Antigens (Ag):
1. type A has A antigens
2. Type B has B antigens
3. type AB has both A & B
4. type O has neither Ag
d. Rh: Rh+ has antigen
Rh- lacks antigen
(ABO & Rh: major antigens involved in antibody incompatibility)
Erythroblastosis Fetalis, continued ….
4. At birth, baby’s blood may mix
with mom’s (~40%)
5. Mom makes antibodies to Rh+
6. During succeeding pregnancies,
antibodies cross placenta
7. Cause baby’s blood to agglutinate
Erythroblastosis Fetalis, continued …
9. Rhogam
a. antibody formation may be prevented:
“fools” mom’s immune system
b. Rhogam given within 72
hours after fetus “leaves”
c. Currently, Rhogam given to all
Rh- moms every trimester
Twinning mechanisms and Placentation
Full-term Pregnancy