Polyhydramnios

Question 1

Definition

Answer 1

An abnormally large volume of amniotic fluid and It can be classified as mild, moderate and severe.

SDP ≥8cm
AFI ≥25

Mild: 8-11cm
Moderate: 12-15cm
Severe: >16cm

Question 2

Incidence

Answer 2

affects 1% of pregnancies.

Question 3

Causes

Answer 3

• Fetal causes:
o Congenital abnormalities such as oesophageal or duodenal atresia, renal defects, neuromuscular or neurological abnormality.
o Genetic disorders
o Multiple pregnancies
o Congenital infections (parvovirus, rubella, toxo, CMV, syphilis)
o Haematological conditions e.g. rhesus autoimmunisation causing fetal hydrops

• Maternal causes:
o Diabetes
o Hypercalcaemia
o Substance misuse or medications e.g. lithium

• Placental e.g. placental tumours
• Idiopathic (50-60%)

Question 4

If polyhydramnios detected, which investigations should be performed?

Answer 4

1. Detailed anomaly scan
   The anomalies most commonly missed are tracheoesophageal fistula, cardiac septal defects and cleft palate. The prevalence of aneuploidy in fetal anomalies was found to be 10% in a large study.
2. Exclude maternal gestational diabetes with an oral glucose tolerance test
3. If fetal anaemia or fetal hydrops suspected, exclude:
   • Immunological causes (maternal blood group, Rhesus factor, screening for red cell antibodies)
   • Fetomaternal haemorrhage (Kleihauer)
   • Acute Parvovirus infection
   • Haemoglobinopathy
   • TORCH screens are not indicated for women who have polyhydramnios with an otherwise normal ultrasound scan given the low prevalence of TORCH infections and the limited implications on management.

Question 5

When to refer to MFM?

Answer 5

• Suspected fetal anomaly
• Small for gestational age fetus
• Severe or worsening polyhydramnios
• Hydrops
• If severe symptoms: for consideration of therapeutic amniocentesis or amniodrainage before 37 weeks..

Question 6

Antenatal management of polyhydramnios

Answer 6

• No randomised trials have evaluated whether pregnancies complicated by idiopathic polyhydramnios benefit from any method of antenatal surveillance, therefore no additional monitoring is required.
• There is not enough evidence to develop recommendations regarding the timing of delivery. An individualised assessment by the SMO is advised. Patients’ symptoms, preferences and risks of cord prolapse or other complications (e.g. remote locations) must be considered.
• Where a cause has been identified, antenatal surveillance to be directed accordingly

Question 7

Maternal complications from polyhydramnios

Answer 7

• Increasing discomfort, breathlessness and pain
• Risk of cord prolapse
• Malposition
• Prelabour rupture of membranes
• Postpartum haemorrhage
• Preterm labour
• Placental abruption after rupture of membranes
• Higher rates of caesarean section

Question 8

Fetal complications from polyhydramnios

Answer 8

Higher risk of:

• lower apgar scores,
• admission to the neonatal unit,
• higher birthweight
• 2-5 fold increased risk perinatal mortality

Question 9

What advice should be given to women with polyhydramnios?

Answer 9

Counseled re risks of:
preterm labour, cord prolapse, placental abruption, malpresentation, PPH, and fetal abnormality (mainly in severe cases and when associated to other scan findings).

Patients should also be advised that if they have prelabour rupture of membranes they should present immediately for assessment. Women to be informed about knee-chest positioning in the event that membranes rupture.