Abstract
The publication of the closed-loop insulin delivery in pregnant women with type 1 diabetes (CRISTAL) study marks the second randomized controlled trial evaluating the use of hybrid closed loop systems in the pregnancies of women with type 1 diabetes. 1,2 A Comment by Professors Helen Murphy and Eleanor Scott. 1 compares the glycemic outcomes of two randomized controlled trials of automated insulin delivery (AID) systems (CRISTAL with MiniMed 780G and AiDAPT with CamAPS FX). 2,3 They raised concern that at least an additional 5% of time spent in the pregnancy glucose target range ((TIRp) 63–140 mg/dL) is necessary to secure the clinical benefits of a treatment. However, critical analysis of these studies’ data suggests a more nuanced picture.
As Professors Murphy and Scott state, “Treatment benefits are highly dependent on user characteristics, with the greatest benefits seen in those with higher baseline HbA1c.” Indeed, many of the CRISTAL participants had lower A1cs entering into their pregnancies (HbA1c = 6.5%; TIRp 60.5%), whereas those in the AiDAPT study had higher A1cs (HbA1c = 7.7%; TIRp 47%). Professors Murphy and Scott argue that the change in TIRp suggests system superiority. However, the final TIRp’s (66.5% vs. 68.2%) in the CRISTAL and AiDAPT studies are similar, as seen in Figure 1, and the end-of-study HbA1c’s differed by 0.2%. Importantly, also end-of-study time-below-range was similar in the CRISTAL study and the AiDAPT study. In addition, both studies showed less (excessive) gestational weight gain in the group who used a hybrid closed loop system. It is, however, not possible to compare pregnancy outcomes between both studies, as none of the studies were powered for maternal and neonatal outcomes. Real-world data from large national registries may help to inform in the future whether the use of hybrid closed loop systems can improve pregnancy outcomes.
A time in target glucose range according to time of day.
The conclusion, therefore, is, with limited clinical options available, both the MiniMed 780G and CamAPS systems are treatment considerations for managing pregnancies with type 1 diabetes, and for many have been demonstrated to provide benefits in one of several areas, including: glycemic control, a reduction in hypoglycemia, and burden for the user. However, neither system achieved the recommended TIRp of 70% for all women with type 1 diabetes throughout pregnancy, 4 nor are they providing desired maternal and fetal outcomes. Further studies are needed to show the impact of AID on pregnancy outcomes.
The availability of different approaches and technology options for the treatment of type 1 diabetes in pregnancy planning during pregnancy and postpartum can be a positive adjunct in order to personalize the therapy in this vulnerable period and ensure continuity of therapy. The CRISTAL study outcomes, in addition to smaller retrospective cohort studies, 5,6 show that the use of the MiniMed 780G system can be considered safe and enables pregnant women with type 1 diabetes to continue using this system during pregnancy, delivery, and the postpartum period 7 when being supported by clinicians with expertise in the management of diabetes in pregnancy focusing on glycemic goals with experience in system use. Hopefully, AID algorithms in the future will be able to address all the requirements throughout pregnancy to provide outcomes according to the Saint Vincent declaration, providing women with type 1 diabetes outcomes comparable with the general population.