What is the recommended approach for insulin management during labor in patients with diabetes?

Insulin Management During Labour

For women with Type 1 or Type 2 diabetes in active labour, switch from subcutaneous insulin to intravenous insulin infusion with concurrent 10% glucose infusion, maintaining blood glucose between 4.0-7.0 mmol/L (72-126 mg/dL), while for gestational diabetes requiring high-dose insulin (≥0.5 units/kg/day), use the same IV protocol, but discontinue all insulin immediately postpartum. 1

Pre-Labour Preparation

Timing and Scheduling

• Schedule diabetic patients early in the surgical/delivery list to minimize fasting time and reduce risk of dehydration, acidosis, and ketosis 2
• Delivery is recommended by 38-39 weeks' gestation to balance stillbirth risk against neonatal complications 1
• Earlier delivery may be indicated with poor glycemic control, hypertensive disorders, abnormal fetal testing, or fetal growth restriction 1

Pre-Delivery Assessment

• Ensure a written protocol from a diabetologist is available before labour begins 2
• Verify the patient's diabetes type (Type 1, Type 2, or gestational) and current insulin regimen 2
• For insulin pump users, prepare a personalized protocol for pump adaptation or transition to IV insulin 1

During Active Labour: Insulin Protocol by Diabetes Type

Type 1 Diabetes

Critical principle: Never interrupt insulin therapy in Type 1 diabetes due to extremely high risk of ketoacidosis, even with only moderately elevated blood glucose levels. 2, 1, 3

• Switch to IV insulin infusion during active labour with concurrent 10% glucose infusion 1
• Monitor capillary blood glucose hourly during labour 2, 4
• Target glucose range: 4.0-7.0 mmol/L (72-126 mg/dL) 1
• Insulin requirements typically decrease to zero during first stage labour but return during active pushing in second stage 1
• For pump users: preferably change to IV insulin, though pump retention is possible with adapted protocol 1
• Monitor for ketosis if glucose control becomes difficult 1

Type 2 Diabetes

• Switch to IV insulin infusion during active labour with concurrent 10% glucose infusion 1
• Often require higher insulin doses than Type 1 patients due to insulin resistance, sometimes necessitating concentrated insulin formulations 1
• Use same glucose monitoring frequency (hourly) and targets as Type 1 diabetes 2, 1
• Insulin rates typically range 0-5 units/hour based on glucose levels 1

Gestational Diabetes

The approach differs dramatically based on insulin requirements during pregnancy:

• High-dose insulin (≥0.5 units/kg/day): Use IV insulin-glucose protocol in 47% of these patients 4
• Diet-controlled or low-dose insulin (<0.5 units/kg/day): Only 8% require IV protocol during labour 4
• Continue hourly glucose monitoring even if not on IV insulin 4
• Target same glucose range: 4.0-7.0 mmol/L (72-126 mg/dL) 1

Glucose Infusion Management

Rationale and Protocol

• Administer 10% glucose infusion alongside insulin to prevent maternal hypoglycemia and ketosis due to fasting and increased energy demands during active labour 1, 3
• Continue glucose infusion throughout second stage labour during active pushing 1
• The glucose infusion provides approximately 6 gm/hour 5

Monitoring Requirements

• Measure capillary blood glucose hourly from induction until delivery 2, 4
• For general anesthesia cases, measure every 30 minutes from induction until fully conscious 2
• Administer ultra-rapid insulin analogue bolus if capillary blood glucose exceeds 10 mmol/L (180 mg/dL) 2

Electrolyte Monitoring: Critical Potassium Management

Insulin stimulates potassium movement into cells, potentially causing life-threatening hypokalemia with IV insulin administration. 6

Monitoring Protocol

• Check baseline potassium level before starting insulin infusion 3
• Ensure normal potassium levels (3.5-5.0 mEq/L) before initiating insulin therapy 3
• Monitor potassium levels every 4-6 hours during labour while on insulin drip 3
• Continue monitoring every 6 hours for 24 hours post-delivery if insulin infusion continues 3
• Untreated hypokalemia can cause respiratory paralysis, ventricular arrhythmia, and death 6

Immediate Postpartum Management (First 24-48 Hours)

Type 1 Diabetes

Insulin requirements decrease dramatically immediately after placental delivery. 1

• Resume basal-bolus insulin scheme with significant dose reduction: either 80% of pre-pregnancy doses OR 50% of end-pregnancy doses 2, 1
• Never discontinue basal insulin - if electronic syringe is stopped, immediately resume slow insulin if last injection was >24 hours ago 2
• For pump users: restart pump as soon as electronic syringe is stopped 2
• Target blood glucose: 6-8.8 mmol/L (110-160 mg/dL) after vaginal delivery 2
• Use slightly lower targets after cesarean section to support wound healing 2
• Be vigilant for hypoglycemia during breastfeeding due to high metabolic demands 6, 7

Type 2 Diabetes

• Continue insulin at half-dose while awaiting diabetologist advice 2
• Target same blood glucose range: 6-8.8 mmol/L (110-160 mg/dL) 2
• Patients can continue metformin and glibenclamide even if breastfeeding 2
• Monitor for hypoglycemia during breastfeeding 7

Gestational Diabetes

Stop all insulin therapy immediately postpartum - insulin resistance resolves rapidly after placental delivery, making continued insulin unnecessary and potentially dangerous. 8

• Continue monitoring blood glucose before meals and 2 hours after meals for 48 hours 2, 8
• Only restart treatment if:
  • Fasting blood sugar >126 mg/dL (7 mmol/L) OR
  • Post-prandial blood sugar >200 mg/dL (11 mmol/L) 2, 8
• Mandatory diabetologist consultation before reinitiating any treatment 8
• Schedule 75-gram oral glucose tolerance test at 6-12 weeks postpartum (do not use HbA1c) 8

Evidence-Based Outcomes

Neonatal Hypoglycemia Rates

• Using standardized IV insulin-glucose protocol: overall neonatal hypoglycemia rate 7.3% (4.9% in GDM offspring, 10.9% in pre-existing diabetes offspring) 4
• Without protocol: neonatal hypoglycemia rates as high as 48% in Type 1 diabetes and 19% in gestational diabetes 4
• Recent equivalence trial showed permissive control (70-180 mg/dL) had similar neonatal outcomes to tight control (70-110 mg/dL), with 25% vs 29% neonatal hypoglycemia rates respectively 9

Maternal Glucose Control

• Using standardized protocol: maternal hypoglycemia rate was low (6.6% with glucose ≤3.5 mmol/L, only 1.5% ≤3.0 mmol/L) 4
• Only 13.9% of women had blood glucose ≥7.0 mmol/L pre-delivery 4
• Approximately 48% of insulin-dependent patients may not require any insulin during induction despite large antenatal requirements 5

Critical Pitfalls and How to Avoid Them

Life-Threatening Errors

1. Interrupting insulin in Type 1 diabetes: Can rapidly cause ketoacidosis even with moderately elevated glucose 2, 1, 3

   • Prevention: Never stop basal insulin; have standing orders for immediate resumption when IV insulin stops

2. Excessive postpartum insulin dosing: Causes severe hypoglycemia as insulin requirements drop 50-80% after placental delivery 2, 1

   • Prevention: Use predetermined dose reduction protocols (50-80% reduction for Type 1,50% for Type 2)

3. Ignoring hypokalemia risk: IV insulin can cause fatal cardiac arrhythmias 3, 6

   • Prevention: Mandatory potassium monitoring every 4-6 hours during IV insulin infusion

Common Management Errors

1. Inadequate glucose infusion during labour: Leads to maternal hypoglycemia and ketosis despite fasting 1, 3

   • Prevention: Always pair IV insulin with 10% glucose infusion

2. Continuing insulin in gestational diabetes postpartum: Unnecessary and dangerous after placental delivery 8

   • Prevention: Stop all insulin immediately postpartum in GDM; monitor only

3. Using HbA1c for postpartum diabetes screening: Not recommended by guidelines 8

   • Prevention: Use 75-gram OGTT at 6-12 weeks postpartum