Amniotic fluid disorders — structured SAQ (15 marks)

(a) Definition and grading (3 marks)

• Definition — polyhydramnios in a singleton is a deepest vertical pocket of 8 cm or more, or an amniotic fluid index of 24 cm or more (SMFM #46). By true volume it is over 2000 mL. (1.5 marks)^[1][2]
• This finding — DVP 11 cm, AFI 29 cm meets both criteria; this is mild polyhydramnios (AFI 25 to 30 cm, DVP 8 to 11 cm). (1 mark)^[2]
• Method note — state that you measured the single deepest pocket for surveillance rather than the AFI, because the AFI over-diagnoses oligohydramnios and drives interventions without outcome benefit. (0.5 marks)^[3]

(b) Structured workup (4 marks)

One mark per element, maximum four. ^[1]

• Confirm and re-scan — senior sonographer; re-measure the deepest pocket with colour Doppler off (colour labels 37% of normal volumes as oligohydramnios; the same caution applies to over-calling polyhydramnios).^[2]
• Detailed anatomy scan — look for the swallowing failure (gastrointestinal obstruction such as duodenal or oesophageal atresia, CNS lesion such as anencephaly), hydrops and structural anomaly.^[1]
• Maternal diabetes — repeat the 75 g oral glucose tolerance test (or review HbA1c); polyhydramnios can be the first sign of late-onset gestational diabetes.^[1]
• Infection and alloimmunisation — maternal TORCH and parvovirus serology; indirect Coombs / antibody screen. If a structural anomaly or growth restriction is found, offer chromosomal microarray (SMFM #52).^[4]

(c) Management — SMFM #46 (5 marks)

Name the two interventions to avoid AND the amnioreduction indication for full marks. ^[1]

• Mild idiopathic polyhydramnios — no antenatal fetal surveillance is required (GRADE 2C); labour should be allowed to occur spontaneously at term; induction, if planned, not before 39 weeks; mode of birth by usual obstetric indications (GRADE 1C).^[1]
• Amnioreduction — recommend only for severe maternal discomfort, dyspnoea, or both, in the setting of severe polyhydramnios (GRADE 1C). This woman is asymptomatic with mild disease, so amnioreduction is not indicated.^[1]
• Indomethacin — should not be used for the sole purpose of decreasing amniotic fluid in polyhydramnios (GRADE 1B); ductus arteriosus concern after 32 weeks and lack of proven benefit.^[1]
• Severe polyhydramnios — recommend birth at a tertiary centre because of the significant possibility of a fetal anomaly (GRADE 1C).^[1]

(d) Maternal complications and intrapartum preparation (3 marks)

• Complications (1 mark per pair, max 3) — malpresentation; preterm prelabour rupture of membranes and cord prolapse; placental abruption (sudden decompression); preterm birth; postpartum haemorrhage from an overdistended, atonic uterus.^[1][2]
• Intrapartum preparation — plan an active third stage and have uterotonics ready (the uterus that has held excess fluid does not clamp down); anticipate malpresentation and the need for theatre access.^[1]