Continuous glucose monitoring targets in pregnant women with type 1 diabetes

This study reviewed the use of continuous glucose monitoring (CGM) in pregnancy for women with type 1 diabetes (T1D). 

Continuous glucose monitoring (CGM) automatically tracks blood glucose levels throughout the day and night. A CGM works through a tiny sensor inserted under the skin. The sensor tests glucose every few minutes. A transmitter wirelessly sends the information to a monitor. CGM is associated with improvements in blood glucose control. Glucose control is measured by keeping blood glucose in target range which is 3.5-7.8 mmol/l (63-140 mg/dl). The goal is to increase the CGM time in range (TIR) while reducing time above range (TAR; high blood glucose levels), time below range (TBR; very low blood glucose levels or hypoglycemia). 

In pregnant women with T1D, it is important to maintain TIR so the baby will be born healthy and with no complications. 

This article reviewed the importance of CGM and TIR in pregnancy for women with type 1 diabetes (T1D). 

TAR reduces from 40% (10 h a day) to 33% (8 h) during the first to the third trimester. TIR over 70% (16 h a day) of the time is only achieved in the last weeks of pregnancy. 

It is not recommended that patients spend more than 4% or 1h daily below the threshold (3.5 mmol/l). It is already known that high blood glucose leads to complications in pregnancy and for the baby. However, very low blood glucose can be also very dangerous. This risk increases around week 16 of pregnancy. 

A 5% lower TIR and 5% higher TAR during the second and third trimesters is associated with increased risk. These risks include large infants, low blood glucose for infants at birth and intensive care admissions for the baby.

For the best outcomes for babies, women should aim for a TIR of more than 70% (16 h, 48 min) from as early as possible during pregnancy.

This study found that CGM is very important to monitor blood glucose levels in pregnant women with T1D.