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Monitoring glucose levels during pregnancy

Continuous glucose monitoring

In Scotland, CGM is available for all people with T1DM, and for all women with insulin-treated T2DM in pregnancy.

 

Ensure that all women with T1DM have access to CGM during pregnancy.

Consider CGM in pregnant women with T2DM.

There are instances where women with GDM and clinical teams may jointly consider use of CGM, for example in those who are unable to undertake home blood glucose monitoring, or where remote monitoring would be advantageous. Compared with T1DM and T2DM there is a smaller body of evidence examining the use of CGM in GDM, and the majority of studies do not differentiate between the type of CGM, nor between those who manage glucose levels with insulin, metformin or diet. Furthermore, while the evidence is mixed, most studies do not report benefits in perinatal outcomes associated with CGM use in women with GDM. There is therefore insufficient evidence to support a recommendation for the routine use of CGM in women with GDM.

 

Glycated haemoglobin (haemoglobin A1c)

 

For women with pre-existing diabetes (T1DM or T2DM), HbA1c should be measured at booking as this will help to predict risk of congenital anomalies, large for gestational age (LGA) infants and macrosomia.

Monitoring change in HbA1c between the first and third trimester should be considered in those with pre-existing diabetes.

Measurement of HbA1c in women with risk factors for GDM may be used to exclude pre-existing T2DM. This can predict women at highest risk of GDM later in pregnancy but is not a diagnostic test for GDM.

Use continuous glucose monitoring metrics, such as time in range (TIR) or Glucose Management Indicator (GMI) to assess glucose levels during pregnancy.

 

Glycaemic targets during pregnancy

Blood glucose

 

In pregnant women with GDM, glucose levels close to those in people without diabetes should be encouraged to help reduce Caesarean birth rates, the risk of LGA infants, neonatal hypoglycaemia and pre-eclampsia. This may result in the increased use of medication and requires more intensive follow up.

The following glucose levels are recommended for women with GDM:

  • fasting glucose level <5.5 mmol/L
  • one-hour postprandial glucose level <8 mmol/L, and
  • two-hour postprandial glucose level <7 mmol/L.

Where measured, women with GDM who are using insulin should aim to keep preprandial glucose levels <5.5 mmol/L.

In pregnant women with pre-existing diabetes, glucose levels close to those in people without diabetes should be encouraged as this may reduce the risk of LGA infants and the need for emergency Caesarean sections. Levels should be individualised and balanced with risk of hypoglycaemia.

  • For pregnant women with T1DM or T2DM the glucose targets for women with gestational diabetes provide general guidance.
  • CGM should be used to assess overall glycaemic levels and women should aim to spend at least 70% time in range (3.5–7.8 mmol/L).

Glycated haemoglobin (haemoglobin A1c) and later pregnancy risk prediction

Third trimester perinatal death rates stratified by HbA1c and type of diabetes

HbA1c (mmol/mol) Third trimester perinatal death rate (%)
  Type 1 diabetes Type 2 diabetes
<43 0.6 0.9
44-52 1.2 2.7
53-64 1.7 4.0
64-74 1.7 4.9
75-85 8.3 10.0

 

For pregnant women with T1DM or T2DM, individualised prepregnancy HbA1c targets should be maintained during pregnancy while avoiding excessive hypoglycaemia.

There is insufficient evidence to support an HbA1c target in women with GDM.

HbA1c ≥48 mmol/mol during the third trimester should be considered a marker of clinical risk.

 

Ketone monitoring

 

Advise pregnant women with T1DM to check blood ketones if blood glucose level is ≥10 mmol/L or during illness.

 

Ensure that local protocols for ketone monitoring and management of diabetic ketoacidosis are followed.

 

 

Timing of birth

Discuss the timing and mode of birth with pregnant women with diabetes during antenatal appointments as early as possible in the pregnancy, with decisions being made in the third trimester.

 

Advise pregnant women with T1DM or T2DM and no other complications to have an elective birth by induction of labour, or by elective Caesarean section if indicated, between 37+0 weeks and 38+6 weeks of pregnancy.

 

Advise women with gestational diabetes to give birth no later than 40+6 weeks, and offer elective birth (by induction of labour, or by Caesarean section if indicated) to women who have not given birth by this time.

 

Consider elective birth before 40+6 weeks for women with gestational diabetes if there are maternal or fetal complications.