Safety of Isophane (NPH) Insulin in Pregnant Patients with Diabetes

Evidence Supporting NPH Insulin Use in Pregnancy

The American Diabetes Association recommends that insulin is the preferred agent for management of both type 1 and type 2 diabetes during pregnancy, with NPH insulin being a safe option 1, 2, 4
None of the currently available human insulin preparations, including NPH insulin, have been demonstrated to cross the placenta, making them safe options for pregnant patients 2, 3

For pregnant individuals with type 1 diabetes, insulin should be used to manage the condition without exception, and either multiple daily injections or insulin pump technology can be used effectively 2, 4, 5
Pregnant individuals with type 1 diabetes have an increased risk of hypoglycemia in the first trimester due to altered counter-regulatory responses 3, 5
For type 2 diabetes in pregnancy, insulin is the preferred treatment, and NPH insulin can be used as part of a basal-bolus regimen or in combination with rapid-acting insulin 2, 6, 7

Early pregnancy is characterized by enhanced insulin sensitivity and lower glucose levels, which may require lower insulin doses, with insulin requirements increasing linearly from around 16 weeks 8
Insulin requirements typically result in a doubling of daily insulin requirements compared to pre-pregnancy, and level off toward the end of the third trimester 8
Insulin requirements drop rapidly with delivery of the placenta 2, 3

Frequent blood glucose monitoring and insulin dose adjustments are necessary throughout pregnancy due to changing insulin requirements 2, 4

Hypoglycemia risk is increased during pregnancy, particularly in the first trimester for those with type 1 diabetes 3

Recommended glucose targets for pregnant women with diabetes include fasting glucose of 70–95 mg/dL, one-hour postprandial glucose of 110–140 mg/dL, and two-hour postprandial glucose of 100–120 mg/dL 8
A target A1C of <6% is optimal during pregnancy if it can be achieved without significant hypoglycemia 8

Pregnant individuals with type 1 or type 2 diabetes should be prescribed low-dose aspirin 100–150 mg/day starting at 12 to 16 weeks of gestation to lower the risk of preeclampsia 2, 3
Referral to a specialized center offering team-based care is recommended when available for pregnant individuals with diabetes 2, 3
Education about hypoglycemia prevention, recognition, and treatment is essential for pregnant patients using insulin and their family members 4