Insulin in Pregnancy, Labour and After Delivery

Targets, and the Two Documents That Set Them

The tool titrates to the ADA and ACOG figures, which are the ones the Indian national protocol also uses for fasting and 2-hour values. In labour it prints the NICE and JBDS band of 72 to 126, which is what the infusion triggers below are written against, and names the ACOG band beside it.

1. Two Ways to Start Insulin in Gestational Diabetes

• The national protocol, MoHFW 2018. After two weeks of medical nutrition therapy, a 2-hour post-meal reading of 120 or above starts treatment. Human Premix 30/70, one dose 30 minutes before breakfast: 4 units for a post-meal reading of 120 to 160, 6 units for 160 to 200, 8 units above 200. Add 2 units every third day: before breakfast if the post-meal reading is high, before dinner if the fasting reading is high. Metformin 500 mg twice daily, to 2 g, is permitted from 20 weeks. A woman needing more than 20 units a day, or more than 2 g of Metformin, is referred to a higher centre.
• The weight-based approach, ACOG 190 and ADA. Fasting readings above target are answered with bedtime NPH at 0.1 to 0.2 U/kg; post-meal readings above target with Regular or a rapid analogue before that meal, at 1 unit per 10 to 15 g of carbohydrate, or 2 to 4 units to start. A full regimen, where both are high, is 0.7 to 1.0 U/kg/day divided.
• Which to use. The premix start is simple, cheap and works for the woman whose post-breakfast reading is the problem. It fits the fasting reading badly, because the intermediate fraction of a morning dose has gone by 3 a.m., and a fasting glucose that stays high on a morning premix needs the evening dose the protocol adds, or a bedtime NPH.

2. Pre-existing Diabetes: the Requirement Climbs

• ACOG 201 sizes the total by trimester: 0.7 to 0.8 U/kg/day in the first, 0.8 to 1.0 in the second, 0.9 to 1.2 in the third. About half is basal and half prandial. The dose that was right at 20 weeks is short at 30, and a woman whose doses have not been raised since booking is behind.
• A fall in requirement after 36 weeks is not good news. It is one of the signs of placental insufficiency and needs fetal surveillance, not a smaller dose and a note.
• Insulins with pregnancy data: NPH, Regular, Aspart, Lispro and Detemir. Glargine U-100 has observational data in several hundred pregnancies with no signal of harm, and ADA does not require a woman stable on it to change. Degludec, Glargine U-300 and Glulisine have limited data. Oral agents other than Metformin stop; Glibenclamide crosses the placenta and gives more neonatal hypoglycaemia and macrosomia than insulin.
• Hypoglycaemia awareness is lost in the first trimester in Type 1 diabetes, and severe episodes cluster there. The partner is taught glucagon at the booking visit.

3. Antenatal Corticosteroids

• The curve: the glucose rises from the evening of the first dose, peaks on days 2 and 3, and is back to baseline by day 5 or 6. ACOG says to anticipate the increase over five days; it does not give numbers.
• Mathiesen (2002) tested a schedule on the subcutaneous doses: day 1, raise the evening insulin by 25%; days 2 and 3, all doses by 40%; day 4, by 20%; day 5, by 10 to 20%; days 6 and 7, back to the pre-steroid dose. JBDS (2017, updated 2022) expects a 40 to 50% increase over the course, or runs a variable rate intravenous infusion from the first steroid dose with a target of 72 to 140 mg/dL (4 to 7.8 mmol/L) where hourly monitoring can be done.
• The woman not on insulin is monitored four to six times a day for five days. There is no guideline threshold for starting insulin during the course; a reading persistently above 140 is a reasonable one and the tool says so.

4. Labour and the Operation

• JBDS and NICE: hourly capillary glucose from established labour, target 72 to 126 mg/dL. Type 1 diabetes starts the variable rate infusion at established labour. Type 2 and gestational diabetes start it after two consecutive readings above 126. Preparation: 50 units of soluble insulin in 50 mL of 0.9% sodium chloride, 1 unit per mL, with 5% dextrose alongside.
• ACOG 201: 5% dextrose at 100 to 150 mL/h, and Regular insulin intravenously at 1.25 U/h once the glucose exceeds 100, to hold it below 110.
• The national protocol, where there is no syringe pump: Regular insulin added to 500 mL of normal saline, run at 100 mL/h (16 drops a minute), the number of units set by the glucose: none at 90 to 120, 4 units at 120 to 140, 6 at 140 to 180, 8 above 180. Glucose two-hourly. The morning insulin and Metformin are withheld on the day of induction.
• Elective caesarean: insulin as usual the day before, first on the morning list, nothing subcutaneous that morning, and the infusion from about 6 a.m. in Type 1 diabetes or if the glucose is above 126. Emergency caesarean: the question is what long-acting insulin is already in her; a dose given within 12 hours is still working through the operation and recovery with no meal to meet it.
• Tell the paediatric team before the delivery. The neonate feeds within 30 minutes and has a glucose check 2 to 4 hours after birth (NICE). That is arranged before the cord is cut, not after.

5. After the Placenta

• The postpartum test is the action item of the whole admission. MoHFW: a 75 g oral glucose tolerance test at 6 weeks. ADA: 4 to 12 weeks, then every 1 to 3 years for life. About half of women with gestational diabetes develop Type 2 diabetes within a decade, and the window in which that is preventable opens now. A line in the discharge summary asking someone else to arrange it is not an appointment.
• Contraception before the next pregnancy is part of the discharge, because the next pregnancy should begin with an HbA1c below 6.5% and folic acid already started, and that cannot be arranged after conception.

6. What This Tool Does Not Cover

• Diagnosis. The DIPSI test and when to do it are in the Pregnancy Timeline.
• Ketoacidosis. The Ketoacidosis and Hyperosmolar State Pathway, remembering that in pregnancy it is diagnosed at a lower glucose.
• Insulin outside pregnancy. The Inpatient Insulin Protocol for the ward, and Outpatient Diabetes Management for the clinic.
• Insulin pumps, and the obstetric decisions themselves.