TOG - Polyhydramnios in singleton pregnancies

Question 1

What is the prevalence of aneuploidy in severe polyhydramnios?

Answer 1

10-20%

Question 2

What is the incidence of polyhydramnios?

Answer 2

0.2-3.9%

Question 3

In what % of cases despite investigation does polyhydramnios remain unexplained?

Answer 3

50-60%

Question 4

What is the increase in perinatal mortality and morbidity with unexplained polyhydramnios?

Answer 4

2-5x

Question 5

What is the pattern of amniotic fluid throughout pregnancy?

Answer 5

Increases until 33/40
Plateaus 33-38/40
Then declines

Question 6

What are the general upper limits for AFI and DVP across all gestations?

Answer 6

AFI 25cm

DVP 8cm

Question 7

What are the maternal causes of polyhydramnios?

Answer 7

• Uncontrolled diabetes mellitus (pre-gestational and gestational)
• Rhesus and other blood group isoimmunisation leading to immune hydrops
• Drug exposure, e.g. lithium leading to fetal diabetes insipidus

Question 8

What are the fetal causes of polyhydramnios?

Answer 8

• Structural/congenital malformations
• Chromosomal and genetic abnormalities, e.g. trisomies, Beckwith–Wiedemann syndrome, fetal akinesia-dyskinesia syndrome
• Congenital infections, e.g. toxoplasma, rubella, CMV,
  and parvovirus
• Macrosomia
• Fetal tumours, e.g. teratomas, nephromas, neuroblastoma, and haemangiomas (vascular steal -> cardiac failure)

Question 9

What are the placental causes of polyhydramnios?

Answer 9

Tumours such as chorioangiomas and metastatic neuroblastoma

Question 10

What investigations should be undertaken in polyhydramnios?

Answer 10

• BM/OGTT/HbA1C
• TORCH if signs of fetal infection
• Blood group for RBC antibodies
• Scan for structural anomalies
• Karyotype on individual basis
• ?cx length - ? need steroids

Question 11

When should amniodrainage be considered and what are the risks?

Answer 11

• Symptomatic with resp compromise
• Significant cervical shortening

Risks: 1.5% overall
PTL
Abruption
PROM
Chorioamnionitis
High likelihood of recurrence

Question 12

What is the fetal loss rate with polyhydramnios?

Answer 12

4% rising to 60% if coexisting structural abnormalities

Question 13

What are the rare causes of abnormality when polyhydramnios was deemed to be unexplained antenatally?

Answer 13

• West syndrome (infantile spasms, hypsarrhythmic
  electroencephalogram pattern, and mental retardation)
• Polyuric syndromes such as Bartter syndrome or other genetic syndromes.

Question 14

What specifically needs to be checked neonatally in a pregnancy complicated by polyhydramnios?

Answer 14

Patency of upper GI tract using NG tube