Fetal Physiology

Question 1

Describe the chorion (3)

Answer 1

• First membrane to form
• Contains amnion, embryo, and yolk sac
• Chorion villi - form fetal portion of placenta

Question 2

Describe the amnion (2)

Answer 2

• Closest to fetus - contains amniotic fluid for protection
• Adheres to chorion

Question 3

What are the functions of amniotic fluid? (4)

Answer 3

• Protects fetus
• Maintains temperature
• Promotes musculoskeletal development
• Prevents fetus from adhering to membranes

Question 4

What is contained in the amniotic fluid? (3)

Answer 4

• Fetal cells (basis for amniocentesis)
• Vernix caseosa
• Lanugo

Question 5

How is the amount of amniotic fluid measured?

Answer 5

Ultrasound (AFI - amniotic fluid index)

Question 6

How much amniotic fluid is present at 40 weeks?

Answer 6

700 - 1000 mL

Question 7

Amniotic fluid is initially secreted by the ______

Answer 7

Trophoblast

Question 8

When does fetal urination occur?

Answer 8

23 weeks

Question 9

Amniocentisis allows for evaluation of ______ in preterm labor

Answer 9

Fetal lung maturity

Question 10

Surfactant / albumin ratio of ______ indicates that fetal lungs are mature

Answer 10

> 55

Question 11

Lecithin / sphingomyelin ratio of ______ indicates that fetal lungs are mature

Answer 11

2:1

Question 12

Lecithin / sphingomyelin surfactant allows for ______

Answer 12

Alveolar expansion

Question 13

What is the most important factor of fetal development?

Answer 13

Fetal lung maturity

Question 14

A sudden gush of fluid is suggestive (but not definitive) of ______

Answer 14

Ruptured membranes

Question 15

What can cause a false positive in a ruptured membrane test?

Answer 15

Bloody show / lubricant

Question 16

Describe the test used to determine ruptured membranes (2)

Answer 16

• Vaginal secretions are acidic - turn nitrazine paper YELLOW (membranes intact)
• Amniotic fluid is basic - turns nitrazine paper BLUE (membranes ruptured)

Question 17

What factors confirm ruptured membranes? (3)

Answer 17

• Steady leakage of amniotic fluid
• Pooling of nitrazine positive fluid seen via speculum exam
• Ferning (dried amniotic fluid crystals) upon microscopic exam of fluid

Question 18

Presence of how much fluid is considered polyhydraminos?

Answer 18

> 2000 cc

Question 19

What are the possible causes of polyhydramnios? (2)

Answer 19

• Esophageal atresia - fetus can’t swallow fluid
• Twins - greater fluid volume needed

Question 20

Presence of how much fluid is considered oligohydramninos?

Answer 20

< 400 cc

Question 21

What are the possible causes of oligohydramnios? (3)

Answer 21

• Fetal hypoxia - decreased renal blood flow / urine volume
• Postdated placenta - dehydration causing decreased urine
• Potter’s syndrome - decreased kidney function / urine volume

Question 22

When is the umbilical cord formed?

Answer 22

5 weeks

Question 23

Describe the composition of the umbilical cord

Answer 23

• 2 umbilical arteries
• 1 umbilical vein

Question 24

The umbilical arteries carry ______ blood

Answer 24

Deoxygenated

Question 25

The umbilical vein carries ______ blood

Answer 25

Oxygenated

Question 26

Umbilical vessels are surrounded by ______

Answer 26

Wharton's jelly - protects vessels from compression

Question 27

What is ductus venous?

Answer 27

A temporary blood vessel that connects the umbilical vein to the inferior vena cava in the fetus

Question 28

What is foramen ovale?

Answer 28

A temporary hole between the atria that allows blood to bypass the fetal lungs

Question 29

What is the pathway of fetal circulation?

Answer 29

Ductus venous --> inferior vena cava --> right atrium --> foramen ovale --> left atrium

Question 30

Fetal CO2 is excreted into the ______

Answer 30

Maternal blood stream

Question 31

Where does the highest available oxygen concentration travel to in the fetus?

Answer 31

Brain / heart - lesser amounts to abdominal organs / lower body

Question 32

What is a true knot?

Answer 32

A knot in the umbilical cord

Question 33

What is nuchal cord?

Answer 33

Umbilical cord wrapped around the fetal neck

Question 34

What are the purposes of the placental membrane? (2)

Answer 34

- Separates maternal and fetal blood - CANNOT be mixed - Allows for exchange of gases, nutrients, and electrolytes

Question 35

What hormones are produced by the placenta? (4)

Answer 35

- Progesterone - Estrogen - hCG - human chorionic gonadotropin - hPL - human placental lactogen

Question 36

What are the functions of progesterone? (2)

Answer 36

- Facilities implantation - Decreases uterine contractility

Question 37

What is the function of estrogen?

Answer 37

Stimulates enlargement of breasts / uterus

Question 38

What is the function of hPL?

Answer 38

Promotes fetal growth by regulating glucose available to fetus

Question 39

When does the placenta become fully functional?

Answer 39

8 - 10 weeks

Question 40

Placental function depends on ...

Answer 40

Adequate maternal BP to supply circulation

Question 41

How can optimal circulation be achieved during pregnancy?

Answer 41

Lying on the left side

Question 42

What is the normal size of the placenta?

Answer 42

- 15 - 20 cm diameter - 2 - 5 cm thick

Question 43

What is the average weight of the placenta?

Answer 43

500 grams

Question 44

Describe chorioamnionitis (2)

Answer 44

- Infection of the membranes (chorion and amnion) - Vasoactive prostaglandins interfere with placental perfusion