Oligohydramnios

Question 1

What is oligohydramnios

Answer 1

Low level of amniotic fluid during pregnancy

Amniotic fluid index <5th centile for the gestational age

Question 2

What percentage of pregnancy have oligohydramnios?

Answer 2

4.5%

Question 3

Describe how the volume of amniotic fluid changes till term?

Answer 3

Volume of amniotic fluid steadily increases until 33 weeks gestation

Plateaus from 33-38 weeks and then declines

Question 4

What is normal volume of amniotic fluid at term

Answer 4

500ml

Question 5

What is amniotic fluid made of?

Answer 5

Comprised of foetal urine output with small contributions from the placenta and foetal secretions (eg. resp)

Question 6

Describe the cycle of amniotic fluid

Answer 6

Foetus breathes and swallows the amniotic fluid

Gets processed, fills the bladder and is voided and the cycle repeats

Question 7

What causes oligohydramniois

Answer 7

Anything that reduces the production of urine, blocks output from the foetus or rupture of the membranes (allowing the fluid to leak)

Preterm prelabour rupture of membranes
Placental insufficiency 
Renal agenesis
Non-functioning foetal kidneys
Obstructive uropathy 
Genetic/chromosomal abnormalities 
Viral infections

Question 8

How is oligohydramnios diagnosed?

Answer 8

Ultrasound examination

Amniotic fluid index - measuring maximum cord free vertical pocket of fluid in four quadrants of the uterus and adding them together

Maximum pool depth - vertical measurement in any area

Question 9

What is important to enquire about in the history of oligohydramnios

Answer 9

Symptoms of leaking fluid and feeling damp all the time - new urinary incontinence

Question 10

What examinations are required for oligohydramnios

Answer 10

Measure the symphysis fundal height

Perform a speculum examination - pool of liquor seen in the vagina

Question 11

What investigations are required for oligohydramnios

Answer 11

USS - assess for liquor volume, structural abnormalities, renal agenesis and obstructive uropathy
Measure foetal size, small babies result from placental insufficiency which also causes oligohydramnios. May be a rise in pulsitiy index of the umbilical artery doppler in placental insufficiency

Karyotyping - in early and unexplained oligohydramnios

When considering ruptured membranes as a cause of oligohydramnios - IGFBP-1 in the vagina. This protein is found in amniotic fluid and if detected is strongly suggestive of membrane rupture

Question 12

Describe the management of ruptured membranes

Answer 12

If oligohydramnios is due to ruptured membranes, labour is likely to commence within 24-48hrs

In cases of preterm rupture of membranes where labour doesn’t start automatically, induction of labour should be considered around 34-36weeks

A course of steroids should be given to aid foetal lung development and antibiotics to reduce risk of ascending infection

Question 13

Describe management of placental insufficiency

Answer 13

Timing of delivery depends on number of factors

• rate of foetal growth
• umbilical artery and middle cerebral artery doppler status
• cardiotocography

36-37 Week delivery

Question 14

Describe the prognosis of oligohydramnios

Answer 14

Poor in second trimester
Premature rupture of membranes with subsequent premature delivery and pulmonary hypoplasia - significant respiratory distress at birth

Question 15

What is the purpose of amniotic fluid

Answer 15

Allows foetus to move its limbs in utero (exercise) - without this foetus can develop severe muscle contractures