Oligo/Polyhydramnios

Question 1

Oligohydramnios causes (mnemonic):

Answer 1

DRIPPPPC

• Demise
• Renal abnormality
• IUGR
• Premature rupture of membranes
• Post dates baby
• Potter sequence
  o bilateral renal agenesis + pulmonary hypoplasia
• Pre-eclampsia
• Chromosomal abnormality

Question 2

A 28 year old G2P1 presents to the antenatal clinic in her second trimester to follow up on the results of the ultrasound scan done recently. The diagnosis of polyhydramnios is confirmed.

Which of the following is a risk factor for polyhydramnios?

A. Foetal renal agenesis

B. Post-term gestation

C. Premature rupture of membranes

D. Oesophageal atresia

E. Intrauterine growth restriction

Answer 2

D. Oesophageal atresia

Polyhydramnios is a condition whereby there is an abnormally large level of amniotic fluid during pregnancy. The amniotic fluid index needs to be above 95th percentile which is thought to be >2-3 L of amniotic fluid. It can be caused by any condition that prevents the foetus from swallowing such as oesophageal atresia and CNS abnormalities.

Other risk factors include viral infections, twin-to-twin transfusion syndrome, maternal diabetes, and more. The diagnosis is made through ultrasound scan. Severe and persistent polyhydramnios is associated with increased perinatal mortality leading to congenital malformations, malpresentation, and an increased likelihood of preterm labour as well as a higher incidence of postpartum haemorrhage as the uterus has to contract further to achieve haemostasis

Question 3

Amniotic fluid index: Abnormalities cut-offs:

Answer 3

A normal amniotic fluid index is 5 cm to 25 cm using the standard assessment method.

-Less than 5 cm is considered oligohydramnios
-greater than 25 cm is considered polyhydramnios.

Question 4

polyhydramnios causes (mnemonic):

Answer 4

Causes of polyhydramnios can be due to excessive production of amniotic fluid or insufficient removal of amniotic fluid.

1. Excess production can be due to increased foetal urination:

Maternal diabetes mellitus
Foetal renal disorders
Foetal anaemia
Twin-to-twin transfusion syndrome

2. Insufficient removal can be due to reduced foetal swallowing:

Oesophageal or duodenal atresia
Diaphragmatic hernia
Anencephaly
Chromosomal disorders

ADAMTSDEF
-anencephaly
-diabetes
-aneuploidy
-monozygotic twins
-tumour (choriocarcinoma)
-spina bifida
-duodenal atresia
-esophageal atresia
-facial clefts

(TTP occurs in pregnancy: mutation of ADAMTS13 protein: metalloproteinase)

Question 5

complications (maternal and foetal) of polyhydramnios:

Answer 5

Maternal complications

1. Maternal respiratory compromise due to increased pressure on the diaphragm
2. Increased risk of urinary tract infections due to increased pressure on the urinary system
3. Worsening of other symptoms associated with pregnancy such as gastro-oesophageal reflux, constipation, peripheral oedema and stretch marks
4. Increased incidence of caesarean section delivery
5. Increased risk of amniotic fluid embolism (although this is rare)

Foetal complications

1. Pre-term labour and delivery
2. Premature rupture of membranes
3. Placental abruption
4. Malpresentation of the foetus (the foetus has more space to “move” within the uterus eg breech presentation)
5. Umbilical cord prolapse (polyhydramnios can prevent the foetus from engaging with the pelvis, thus leaving room for the cord to prolapse out of the uterus before the presenting part)

Question 6

treatment of polyhydramnios:

Answer 6

Treatment includes management of any underlying causes (e.g. in maternal diabetes) and amnio-reduction in severe cases.