Oligo/Polyhydramnios

Question 1

What makes up the amniotic fluid?

Answer 1

80% filtrate of maternal plasma

20% fetal - changed by swallowing, urination

Question 2

What is the amniotic fluid index? How is it calculated?

Answer 2

• Measurement of amniotic fluid

- Measure the deepest pocket of amniotic fluid (in cm) in 4 quadrants and add them together

Question 3

What is the AFI criteria for Oligohydramnios?

Answer 3

• AFI < 5cm

- Or if the single deepest pocket is under 2cm

Question 4

What is the AFI criteria for Polyhydramnios?

Answer 4

• AFI > 25cm

- OR if the single deepest pocket is > 8cm

Question 5

What are maternal causes of Oligohydramnios?

Answer 5

Think that 80% of fluid comes from maternal plasma. Anything lowering volume or placental blood flow can cause it

• Placental insufficiency
• ACEI

Question 6

What are fetal causes of Oligohydramnios?

Answer 6

• Think things that would affect fetal urination, which provides 20% of amniotic fluid
• Renal agenesis
• UTI
• Obstruction
• Chronic hypoxia (blood shunted away from kidney to brain)
• Rupture of membranes

Question 7

What are maternal causes of Polyhydramnios

Answer 7

Type I DM - affects chorioamniotic flow

Question 8

What are fetal causes of Polyhydramnios?

Answer 8

• Chromosomal anomaly
• Respiratory (Lung malformation) - can’t keep fluid in lungs
• GI
  a) Duodenal atresia
  b) Tracheoesophageal fistula
  c) Facial abnormality that interferes with swallowing

Question 9

Why do congenital malformations occur in oligohydramnios?

Answer 9

• Amniotic Band Constriction
• Fetus not supported by fluid and fibrous amniotic bands entrap fetal limbs and/or digits
• Facial deformities can occur as well due to lack of support from amniotic fluid