M7U6: AMNIOTIC FLUID

Question 1

What is amnion composed of ?

Answer 1

A single layer of cuboidal epithelial cells

Question 2

What are the primary functions of the amniotic fluid ? (5)

Answer 2

1. Exchange of water and chemicals (electrolytes, nitrogenous compounds, proteins, enzymes, lipids and hormones) between the fetus and maternal circulation
2. Permit proper fetal lung development
3. Stabilization of temperature to protect the fetus from extreme temperature changes
4. Allows fetal movement
5. Serves as a protective cushion for the fetus

Question 3

How is the volume of amniotic fluid regulated ? (3)

Answer 3

1. Production from fetal urine and lung fluid
2. Absorption from fetal swallowing
3. Intramembranous flow

Question 4

What is intramembranous flow of amniotic fluid ?

Answer 4

Absorption of amniotic fluid water and solutes into the fetal blood

Question 5

What is the volume of amniotic fluid at 12 weeks of gestation ?

Answer 5

25-50 mL

Question 6

What is the volume of amniotic fluid at 37 weeks of gestation ?

Answer 6

800-1200 mL

Question 7

When does amniotic fluid formation start in pregnancy ?

Answer 7

The first trimester

Question 8

___ mL of amniotic fluid produced during the first trimester is produced by the ___ and ___ that is derived from the ___

Answer 8

35

Amnion and placenta

Maternal circulation

Question 9

As the gestation progresses in amniotic fluid formation, water and solutes exchange between the fetus and the amniotic fluid through ? (3)

Answer 9

1. Fetal urination
2. Intestinal absorption following fetal swallowing of amniotic fluid
3. Capillary exchange in the pulmonary system alveoli, as the alveoli of the fetal lungs are bathed with amniotic fluid

Question 10

Under formation of amniotic fluid, in the later stages of pregnancy, ___ and ___ play a significant role in the amniotic fluid volume and composition

Answer 10

Fetal swallowing

Urination

Question 11

___ removes water and electrolyte from the amniotic fluid and replaces them through urination with metabolic by-products such as ___, ___, and ___

Answer 11

Fetal swallowing

Urea
Creatinine
Uric acid

Question 12

How is maternal plasma and amniotic fluid exchange similar to fetal swallowing ?

Answer 12

Maternal plasma removed metabolic waste products and replenishes them with water, nutrients, and electrolytes

Question 13

___ is associated with decreased fetal swallowing

Answer 13

Polyhydramnios

Question 14

What is the main diagnosis for polyhydramnios ?

Answer 14

Neural tube defect (NTD)

Question 15

Polyhramnios often indicate fetal distress and congenital malformations in ___ (3)

Answer 15

NTD
rapidly growing fetal edema
Hydrops fetalis

Question 16

Polyhydramnios is secondarily associated with ___ (4)

Answer 16

1. Fetal structure anomalies
2. Cardiac arrythmias (fetal heart failure)
3. Congenital infections
4. Chromosomal abnormalities

Question 17

Polyhydramnios is the term if the amniotic fluid volume exceeds ___ mL

Answer 17

1,200

Question 18

Oligyhydramnios is the term if the amniotic fluid volume is below ___ mL

Answer 18

800

Question 19

___ is associated with increased fetal swallowing

Answer 19

Oligohydramnios

Question 20

Oligohydramnios has a possible indication of ___ (6) resulting in ___ and ___

Answer 20

1. Urinary tract deformities
2. Membrane leakage
3. Donor twin transfusion syndrome
4. Congenital malformation
5. Premature rupture of the amniotic membrane
6. Umbilical cord compression

Decreased heart rate and fetal death

Question 21

What is the ultimate source of amniotic fluid water and solutes ?

Answer 21

Placenta

Question 22

The presence of ___ and ___ is significant because these components serve as biochemical markers to detect NTD

Answer 22

Alpha-fetoprotein

Acetylcholinesterase

Question 23

Once fetal production begins an increase in concentration can be seen in ___ (3)

Answer 23

creatinine
urea
uric acid

Question 24

Once fetal production begins a decrease in concentration can be seen in ___ (2)

Answer 24

glucose

protein

Question 25

In the beginning of fetal production concentrations of these remain unaffected (4)

Answer 25

electrolytes
enzymes
hormones
metabolic end products

Question 26

Describe what may be seen for creatine, urea, glucose, protein, and fern’s test in maternal urine

Answer 26

creatinine: >4 mg/dL; as high as 10 mg/dL
urea: >30 mg/dL; as high as 300 mg/dL
glucose: essentially negative
protein: essentially negative
fern’s test: negative

Question 27

Describe what may be seen for creatine, urea, glucose, protein, and fern’s test in amniotic fluid

Answer 27

creatinine: ≤4 mg/dL
urea: ≤30 mg/dL
glucose: ≤46 mg/dL
protein: 2-8 g/L
fern’s test: positive

Question 28

early antenatal diagnosis of genetic and congenital disorders in fetal gestation (__-__ weeks)

Answer 28

15-18 weeks

Question 29

assess fetal pulmonary maturity later in pregnancy (__-__ weeks)

Answer 29

32-42 weeks