Hybrid Closed Loop Insulin Pumps in Pregnancy

Type 1 diabetes mellitus (T1D) presents challenges during pregnancy, labor and delivery, and postpartum.

“They are high-risk pregnancies with a propensity for hypoglycemia and diabetic ketoacidosis,” says Kevin Borst, DO, co-director of Cleveland Clinic’s Endocrine Disorders in Pregnancy Center. “Our endocrinologists work in conjunction with maternal-fetal medicine physicians to manage all aspects of their care.”

Traditionally, pregnant patients with T1D have managed their condition with insulin injections. However, the advent of hybrid closed loop (HCL) insulin pumps, which were approved by the FDA nearly a decade ago, has changed the landscape of care.

“Insulin pump use is now widely accepted as the gold standard of management for pregnant patients with type 1 diabetes,” says Dr. Borst. “There are sensor-augmented pumps and enhanced technologies that enable these patients to meet the required targets for pregnancy.”

Those targets include:

• Hemoglobin A1c (HbA1c) levels close to 6% going into a pregnancy
• Fasting blood glucose of less than 90 mg/dL
• A two-hour after meal blood glucose target of less than 120 mg/dL

HCL therapy in pregnancy

Hybrid closed loop pumps, also known as automated insulin delivery systems, rely on algorithms that respond to real-time glucose sensor levels, then automatically modulate insulin delivery.

“The pumps buffer patients from a lot of the variability that happens with type 1 diabetes,” says Dr. Borst. “There are many things that can influence a person’s blood sugar, especially during pregnancy. Even if patients do everything right, it’s hard to account for changes in their hormones, activity and stress.”

Dr. Borst cites several studies indicating that the use of insulin pumps during pregnancy is safe and effective:

A 2014 article in the journal Diabetologia presented one of the first studies to suggest insulin pump use was beneficial in pregnancy. It concluded that insulin pump use is associated with better glycemic control without increased risk of severe hypoglycemia or diabetic ketoacidosis.

A 2023 article in the New England Journal of Medicine presented the first landmark study comparing standard insulin therapy to HCL therapy in pregnancy. Among the key results, more than four times as many participants in the closed loop group achieved the goal of 70% in pregnancy-specific target glucose range compared to standard insulin therapy.

A 2024 article in The Lancet: Diabetes & Endocrinology examined whether people with well controlled diabetes going into pregnancies would benefit from the use of hybrid closed loop therapy. The study found that advanced HCL demonstrates multiple secondary benefits, including improved overnight time in the target range, reduced risk of hypoglycemia, decreased risk of hypoglycemia unawareness and improved patient satisfaction.

Case study

The majority of Dr. Borst’s practice is dedicated to management of pregnant women with endocrine disorders, including T1D. During Cleveland Clinic’s Annual Diabetes Day, which provides up-to-date reviews of management strategies and research on the complications of diabetes, he shared a case study highlighting HCL use during pregnancy.

The 30-year-old patient, who was pregnant for the first time, presented at seven weeks gestation. She was first diagnosed with T1D at age 17, and had no known complications, but she was not up to date with screening. Her HbA1c before her first visit with Dr. Borst was 7.7%.

The patient’s therapy regimen was Lantus 30 units qam and Novolog 1 unit per 6 grams of carbohydrates + scale. She checked her blood glucose five to six times daily, and it ranged between 45 mg/dL to 265 mg/dL.

Dr. Borst switched the patient to HCL therapy using Humalog (insulin lispro) with a t:slim X2™ with Control IQ™ Technology pump.

“Traditionally, patients aren’t placed on an insulin pump this early in pregnancy,” says Dr. Borst. “But I felt very comfortable doing so at a center like ours where we have access to diabetes educators, a team of endocrinologists and other resources.”

During the patient’s first week on the HCL pump, her average daily glucose was 119 mg/dL. During week 36 of her pregnancy, her average daily reading was 120 mg/dL.

The patient delivered a healthy boy (spontaneous vaginal delivery) at 37 weeks gestation. Immediately following delivery, her postpartum HCL pump settings were reduced to initial first trimester settings.

“Patients are typically on a huge amount of insulin at the end of their pregnancies,” says Dr. Borst. “As soon a they deliver the baby, their insulin requirements usually drop by 50% or more, and they need to adjust their settings accordingly.”

He also stresses the importance of monitoring and adjusting HCL therapy settings if patients plan on nursing their babies, which can reduce blood sugar levels.

Dr. Borst’s patient remained on the hybrid closed loop pump postpartum and continues to do well, he says.

“Advanced hybrid closed loop insulin pumps are advantageous in patients with type 1 diabetes,” says Dr. Borst. “There has been a spectrum of better outcomes across the board, and the therapy should be considered in young women with type 1 diabetes who are anticipating pregnancy.”