Gestational Diabetes with Polyhydramnios

Gestational diabetes with polyhydramnios is glucose intolerance first found in pregnancy with excess amniotic fluid, defined as amniotic fluid index above 24 cm or deepest vertical pocket above 8 cm.

Fetal polyuria driven by hyperglycaemia is the commonest cause, but anomalies and infection must be excluded.

It matters because it raises the risk of preterm labour, malpresentation, cord prolapse and postpartum haemorrhage.

Usually appears after 28 weeks.

Usually responds to better glucose control.

Idiopathic polyhydramnios coexists in some women.

Women have a tense, large abdomen, breathlessness and discomfort, with fundal height more than 3 cm above dates and difficulty feeling fetal parts.

Leg and vulval oedema.

Distant fetal heart.

The approach is ultrasound with glucose review and a search for other causes.

• Ultrasound: amniotic fluid index above 24 cm (moderate 30 to 34.9 cm, severe 35 cm or above) or deepest pocket above 8 cm.
• Detailed anomaly scan and fetal heart scan.
• 75 g oral glucose tolerance test if not done: fasting 5.1 mmol/L or above, 1 hour 10.0 mmol/L or above, 2 hours 8.5 mmol/L or above; capillary glucose profile.
• Indirect Coombs test, syphilis and TORCH serology, full blood count.

The principle is tight glucose control, relief of symptoms and planned delivery.

• Supportive: rest; admit for severe symptoms; counsel on warning signs of labour and cord prolapse; delivery at a facility with neonatal care.
• Pharmacological: start isophane insulin 0.2 units/kg subcutaneous at bedtime and soluble insulin 4 to 6 units subcutaneous before meals, adjusting by 2 units every 3 days; metformin 500 mg oral with meals to 1 g 12-hourly (maximum 2.5 g daily); indomethacin 25 mg oral 6-hourly for up to 48 hours before 32 weeks for severe symptomatic cases with ultrasound review of the ductus arteriosus; betamethasone 12 mg IM twice, 24 hours apart, if delivery is likely before 34 weeks with insulin increased by 25 to 40 percent for 72 hours; oxytocin 10 IU IM after delivery of the baby and infusion 20 IU in 1 litre sodium chloride 0.9 percent at 125 mL/hour for 4 hours to prevent haemorrhage.
• Procedures: amnioreduction by ultrasound guided needle for severe symptoms, removing up to 2 litres at no more than 1 litre every 20 minutes; controlled amniotomy in labour; delivery at 38 to 39 weeks.
• Special groups: neonates feed within 30 minutes, check glucose at 2 to 4 hours, treat glucose below 2.6 mmol/L with dextrose 10 percent 2 mL/kg IV over 10 minutes; check for oesophageal atresia if the baby has frothing at the mouth.
• Red flags: contractions, rupture of membranes, abdominal pain, breathlessness, reduced fetal movements.
• Follow-up: scan every 2 weeks; glucose profile weekly; 75 g oral glucose tolerance test at 6 to 13 weeks postpartum.