Closed-loop Insulin Delivery In Type 1 Diabetes Pregnancies (CIRCUIT)

This trial will assess the efficacy of the Tandem t:slim X2 insulin pump with Control IQ technology compared with standard insulin delivery plus CGM in pregnant women with type 1 diabetes.

Pregnant women with type 1 diabetes (T1D) require normal or near normal glucose in order to reduce the risks of birth defects, stillbirth, increased birthweight, neonatal hypoglycemia, neonatal death, preterm delivery and preeclampsia. Reducing maternal glucose is extremely difficult due to an increased risk of maternal hypoglycemia. Only 14% of T1D pregnancies achieve pregnancy guideline recommended glucose control, leading to complications related to high maternal glucose exposure in roughly half of newborns.

Maintaining recommended maternal glucose levels during pregnancy reduces the risk of adverse neonatal outcomes to those similar in pregnancies unaffected by T1D. Most insulin pumps in use today are open-loop systems, which means that the user must program the pump to deliver a pre-set amount of insulin. These insulin delivery methods (MDI and open-loop pumps) are usually inadequate to achieve the optimal glucose control necessary for T1D pregnancies and they impart a large time, effort and emotional burden.

Closed-loop systems have been found to be effective in improving glucose control outside of pregnancy when studied in children and adults. A new hybrid closed-loop system, the Tandem t:slim X2 insulin pump with Control IQ technology, recently became commercially available. Trials have demonstrated the efficacy of the Control IQ algorithm for non-pregnant adults and children. Pregnant women were not included in these trials.

The investigators propose the first randomized controlled trial to evaluate the Tandem t:slim X2 insulin pump with Control IQ technology versus standard insulin delivery (MDI or pump) and CGM in pregnant women with T1D. In this trial, the investigators will assess the efficacy of the Tandem t:slim X2 insulin pump with Control IQ technology compared with standard insulin delivery plus CGM in pregnant women with type 1 diabetes.

We are grateful to Tandem Diabetes Care and Dexcom for in-kind donations to this investigator initiated study.

Eligibility Criteria:
Inclusion Criteria:

* Between 18 and 45 years of age (inclusive)
* A diagnosis of type 1 diabetes, as defined by Diabetes Canada, for at least 12 months
* A viable singleton pregnancy confirmed by ultrasound, less than 14 weeks gestation
* Currently on intensive insulin therapy (≥ 3 injections, or Continuous subcutaneous insulin infusion (CSII)
* Willingness to use the study devices throughout the trial
* A1c ≥ 6.2% and \<10% measured any time during pregnancy prior to enrollment
* Able to provide informed consent
* Have access to email

Exclusion Criteria:

* Non-type 1 diabetes
* Current treatment with drugs known to interfere with glucose metabolism as judged by the investigator such as high dose systemic corticosteroids
* Known or suspected allergy to insulin
* Women with nephropathy (estimated glomerular filtration rate \[eGFR\] \<45), severe autonomic neuropathy, uncontrolled gastroparesis or severe proliferative retinopathy, as judged by the investigator, that is likely to interfere with the normal conduct of the study and interpretation of study results
* Total daily insulin dose \<8 or \>250 units/day at screening
* Severe visual or hearing impairment, as judged by the investigator to impact treatment compliance
* Unable to communicate effectively in English or French as judged by the investigator
* Current use of Tandem Control IQ, DIY looping system, 670G in Auto Mode, or alternate closed-loop system as judged by the investigator
* Any reason judged by the investigator that would likely interfere with the normal conduct of the study and interpretation of study results