fetal environment pt 1 (jo copy)

What size should the CRL be when a heartbeat can be seen?

Greater than 5 mm

When should GSD or MSD be measured?

Early as 5 weeks

How accurate is GSD or MSD?

± 10 days

What is the most accurate way to determine the fetal growth rate (FGR)?

Abdominal circumference

What is the normal measurement for the lateral ventricle?

Less than 10 mm

What is included in the fetal environment?

1. Amniotic fluid

2. Umbilical cord

3. Placenta

4. Uterus

what should we look for in the cervix?

cervical incompetence

What is the normal measurement for cervical length in the third trimester?

how do we measure?

always want it to be over 2.5 cm

• transvaginal from internal to external os

too short of a measurement in the 3rd trimester?

less than 2.5 cm

the myometrium should be __________ to the placenta?

hypoechoic

What are focal uterine contractions?

Muscular contractions that move from cervix towards fundus and can be seen on US

what are Braxton Hicks contractions?

false labor

• move from fundus towards cervix

how to differentiate a fibroid vs focal uterine contraction?

• Focal Uterine Contractions- change size and location during the exam

  • sit in anterior portion of placenta-likely a contraction

• Fibroids remain same size and location throughout the exam

how to differentiate between a fibroid and a subchorionic hematoma?

color Doppler!!!

• fibroid will have some internal flow

• Rescan in a few days: Subchorionic hematoma will become more cystic in appearance.

What are the roles of the placenta?

1. Protection

2. Nutrition

3. Respiration

4. Excretion of waste

5. Storage

6. Hormone secretion

placental functions? (in depth- don’t study)

• Protection: filtering harmful substances out of mother’s blood

• Nutrition: nutrient exchange (mother’s blood—> fetus’ blood)

• Respiration: O₂ and CO₂ exchange (mother’s and fetus’ blood)

• Excretion: metabolic waste transfer (fetus’ blood —> mother’s blood) for processing & excretion by mother’s body.

• Storage: stores carbs, proteins, Ca²⁺, & iron; released to fetal blood as needed.

• Hormone Secretion: produced by syncytiotrophoblast; helps maintain pregnancy.

  • HCG, Estrogens, Progesterone

where does fetal blood enter the placenta?

through umbilical cord

when can placental position and configuration be seen sonographically?

by end of 1st trimester

what is the chorionic villus?

functional unit of placenta

• made up of arteries and veins from embryo and intervillous spaces

what are intervillous spaces?

spaces which fill up with maternal blood

What composes the fetal portion of the placenta?

Chorion frondosum (chorionic plate)

What composes the maternal portion of the placenta?

Decidua basalis of endometrium

When maternal environment is poor, the placenta becomes…

More efficient at nutrient, oxygen, and waste product transfer to protect fetus

(T/F) The placenta has an unlimited ability to compensate for a poor maternal environment.

False; There are limits to placentas ability to compensate

What occurs when stresses exceed the ability of the placenta to compensate?

Placenta is damaged and fetus is at risk of IUGR and fetal demise

During the first trimester, the fetus is designed to develop at a…

Low oxygen state

(T/F) More oxygen is required by embryo as development becomes more complex.

True; By this time, placenta will have developed enough to provide for fetus

What is the normal insertion point of an umbilical cord on the placenta?

Near center

What is a battledore placenta?

umbilical cord inserts near edge of placenta

a= normal insertion; b= battledore insertion

What is another term for battledore placenta?

Marginal insertion

What is the significance of a battledore placenta?

Not clinically significant unless cord is delivered before baby causing cord prolapse (leads to hypoxia and fetal demise)

What is a velamentous placenta?

When umbilical cord branches out into separate vessels before actually entering placenta

a= normal; c= velamentous

What is the significance of a velamentous placenta?

Increased risk of fetal hemorrhage in cases of vasa previa

placentomegaly (thick placenta) causes?

• placental hydrops (edema of placental tissue/ ground glass appearance)

• gestational trophoblastic disease

• Beckwith Wiedemann syndrome

• confined placental mosaicism (abnormal karyotype of placenta, but not of fetus)

thin placenta causes?

• maternal HTN/ pre-eclampsia

• placental infarction

• maternal diabetes (type 1)

• abnormal placental development

The placenta is an…

Endocrine gland

What is the function of the hCG secreted by the placenta?

Secreted during first trimester to keep corpus luteum from degenerating so progesterone levels remain high to maintain pregnancy

What is the function of the estrogen secreted by the placenta?

Secreted during second trimester to help maintain pregnancy and prepare breasts for lactation

What is the function of the progesterone secreted by the placenta?

Secreted during second trimester to help maintain pregnancy and prepare breasts for lactation

When would a translabial scan be performed?

When evaluating for bulging membranes

(T/F) As the pregnancy progresses, the texture of the placenta changes as it matures/ages.

True; It ages, but it DOES NOT age at same rate in every pregnancy

Which maternal conditions or habits are known to accelerate the maturation process of the placenta?

1. Diabetes (Type 1)

2. Pre-eclampsia

3. Hypertension

4. Smoking

Which maternal conditions or habits are known to decelerate the maturation process of the placenta?

1. Gestational diabetes

2. Rh isoimmunization

How is the maturity of the placenta evaluated?

1. Grade 0: Homogenous

2. Grade 1: Small cystic spaces

3. Grade 2: Small cystic spaces with calcifications

4. Grade 3: “Cumulous cloud” and heterogenous appearance with calcifications

What does IUGR mean?

Fetal growth restriction

What is the normal thickness of the placenta at it’s midpoint?

2-4 cm

What is placentomegaly?

When placenta exceeds 5 cm in thickness and is called placenta hydrops

How can the age of the placenta be determined just by looking at the thickness?

2 cm thick = 20 weeks gestation, 3 cm thick = 30 weeks gestation, etc.

What is a thin placenta?

When placenta measures less than 1.5 cm in thickness

(T/F) IUGR causes placental thinning.

False; IUGR is a RESULT of placental insufficiency which can also cause placental thinning

What is an accessory or succenturiate placenta?

Smaller lobe of placental tissue connected to main placenta by blood vessels but NOT placental tissue

What are the risk factors associated with an accessory or succenturiate placenta?

1. Increased risk of fetal hemorrhage due to vasa previa

2. Increased risk of retained fetal tissue

3. Increased risk of placental infarctions

What is vasa previa?

Prescence of umbilical cord vessels across internal os and cause increased risk of vessel rupture or hemorrhage during delivery due to vessels in membrane not protected by placental tissue (ruptured membranes)

What is considered a normal placental location?

Anywhere as long as it is more than 2 cm away from internal os of cervix

When should the cervix and placental relationship be evaluated for placental previa?

20 weeks

What is placenta previa?

When placenta will come out first in a vaginal delivery due to it’s close proximity to internal os

What is a low-lying placenta?

When inferior margin of placenta is less than 2 cm from internal os

What is a marginal previa?

When inferior margin of placenta comes up to edge of internal os but does not cover any part of it

What is partial previa?

When inferior margin of placenta partially covers internal os

What is complete previa?

When placenta completely covers internal os

What is abnormal placental attachment (MAP)?

When placental tissue has invaded uterine wall beyond decidua basalis to some degree

What are the risk factors associated with abnormal placental attachment (MAP)?

1. History of C-section

2. Placenta previa

What is placenta accreta?

When placental tissue attaches to myometrium, extending just beyond basal endometrium

What is placenta increta?

When placental tissue invades deeply into myometrium but does not perforate uterine wall

What is placenta percreta?

When placental tissue perforates uterine wall and can invade neighboring tissues

What occurs in 90% of cases of placenta percreta?

Hysterectomy required immediately after C-section

What is the sonographic appearance associated with MAP in the second and third trimester?

1. Anterior placental implantation

2. Loss of myometrial clear zone

3. Swiss cheese appearance or multiple vascular lakes

What is the clear zone measurement that indicates accreta?

Less than 1 mm

What is a subchorionic bleed or hematoma?

Collection of blood between chorion and uterine wall that is seen during first trimester and resolves on its own

What is a subamniotic bleed or hematoma?

Collection of blood between amnion and chorion

what is an intraplacental bleed? what is it caused by?

bleeding within placental tissue

caused by:

• intervillous thrombosis

• Kline’s hemorrhage/ intraplacental cavernae

What is a retroplacental bleed or hematoma?

Collection of blood between placenta and uterine wall that causes placental abruption

What is placental abruption?

Separation of basal plate of placenta (maternal) from uterine wall

• uterus hemorrhages into retroplacental space

How is placental abruption classified?

1. Location

2. Presence or absence of vaginal bleeding

• ex: retroplacental/ central and marginal

or classified by degree of separation:

• ex: partial or complete

What is a retroplacental/ central placental abruption?

Separation behind central portion of placenta, away from placenta edge or margin

• often concealed with no vaginal bleeding

What is a marginal placental abruption?

Separation at edge or margin of placenta

• often apparent with vaginal bleeding

What are the risk factors associated with placental abruption/ hemorrhage?

• Maternal hypertension (HTN)

• prior placental abruption

• short umbilical cord

• uterine anomalies

• retroplacental fibroid

• abdominal trauma

• placenta previa

• smoking

• cocaine/ meth use

What is intervillous thrombosis?

Common and not significant hemorrhage that occurs from tears in chorionic villi vessels and results in mixing of maternal and fetal blood

What is placental infarct?

Focal lesion caused by ischemic necrosis due to occlusion of spinal arteries

What is the sonographic appearance associated with acute placental infarct?

Hypoechoic

What is the sonographic appearance associated with chronic placental infarct?

1. Hypoechoic or cystic

2. Calcifications

What are venous lakes or lacunae?

Irregular anechoic spaces located beneath chorionic plate

What is the presence of numerous prominent lakes associated with?

Placenta accreta

What is the most common non-trophoblastic tumor of the placenta?

Chorioangioma

What is chorioangioma?

Benign, vascular tumor similar to hemangioma

What is the significance of the size of a chorioangioma?

1. Small and solitary: Not significant

2. Large and multiple: May cause severe complications including death

What is the sonographic appearance associated with chorioangioma?

1. Well-defined mass

2. Increased vascularity

When is the umbilical cord formed?

Week 7 gestation

What is the original appearance of the umbilical cord?

1. Two umbilical veins

2. Two umbilical arteries

What is the final umbilical cord configuration?

1. One umbilical vein

2. Two umbilical arteries

What is the function of the umbilical vein?

Carries oxygenated blood from placenta to fetus

Where does the umbilical vein enter the fetus?

Umbilicus and runs lateral to left portal vein

What does the umbilical vein connect to?

Enters portal sinus and connects to ductus venosus, bypassing hepatic circulation

After birth, the umbilical vein forms the…

Ligamentum Teres (Round ligament)

After birth, the ductus venosus forms the…

Ligamentum Venosum

What is the function of the umbilical arteries?

Carry partially deoxygenated blood from fetus to placenta

Where do the umbilical arteries arise from?

Internal iliac arteries and run along sides of fetal bladder to umbilicus where they enter umbilical cord

After birth the umbilical arteries form the…

1. Superior vesicle arteries

2. Median umbilical ligaments

What do the superior vesicle arteries supply blood to?

Bladder

What structures do the median umbilical ligaments connect?

Bladder to anterior abdominal wall