Diagnostic Approaches in Gestational Diabetes and Impact of Ethnicity

Screening and Diagnostic Approaches in Gestational Diabetes (GDM) and the Impact of Ethnicity on Markers of Glycaemia in Pregnancy

Gestational diabetes (GDM) means raised blood glucose found for the first time in pregnancy. GDM is common, particularly in women from minority ethnicities. GDM does not cause any symptoms in the mother. GDM is associated with adverse pregnancy outcomes which can be improved with treatment of GDM. The United Kingdom National Institute for Health and Care Excellence (NICE) recommend pregnant women with one or more risk factors should have a 75g oral glucose tolerance test (OGTT). The OGTT is performed in a clinic with venous plasma glucose measured fasting and at 2 hours. This is resource-intensive, and some women with GDM may be missed by this risk-factor based approach. The International Association of Diabetes and Pregnancy Study Groups (IADPSG 2010) recommends screening all pregnant women with 2-hour, 3 sample (fasting, 1 and 2 hour), 75g OGTT, which is even more resource intensive. Developing more cost-effective and convenient approaches to screening for GDM is a priority.

The researchers will validate a new home-use OGTT system (hOGTT), which measures whole blood glucose in capillary blood ('finger-stick' sample), against the gold standard venous plasma glucose in pregnancy.

The researchers will also investigate the performance of glycated haemoglobin (HbA1c) in screening for GDM. HbA1c is used for diagnosis of diabetes outside of pregnancy, but is currently not recommended for screening for GDM.

The researchers will also investigate relationships between glucose measured in different samples (venous versus capillary), different fractions (plasma versus whole blood), and using different methods in pregnancy.

In a substudy the researchers will investigate: ethnic differences in HbA1c and other glycaemic markers; the contribution of fasting and postprandial glucose handling, diet and ethnicity on HbA1c; and ethnic differences in insulin responses to 75g OGTT in pregnancy.

The researchers will invite pregnant women between 16-34 weeks gestation to participate. The research involves one hospital visit for an OGTT. Participants will have venous blood samples taken fasting and at 1-hour and 2-hours, and at the same times finger-stick blood samples will be tested. The researchers will invite women of Black African, Black Caribbean and White European ethnicity to participate in a substudy in which participants will have extra blood taken and a diet assessment.

If the hOGTT provides accurate results in pregnancy, using it to perform OGTTs at home would make screening for GDM less expensive and more convenient and may facilitate universal screening for GDM. Understanding ethnic differences in HbA1c will help determine if HbA1c is a reliable screening tool for GDM in our ethnically diverse local population.

Inclusion Criteria:

Main study:

• Pregnant woman at least 18 years of age
• 16-34 weeks gestation.
• Booked for pregnancy care at a participating centre
• Able to give informed consent to participate

Substudy:

In addition to the inclusion criteria of main study:

• Women who are of White European, Black African or Black Caribbean ethnicity.

Exclusion Criteria:

Main study

• Unable to give informed consent
• Known pre-pregnancy diabetes
• GDM diagnosed in the current pregnancy

Substudy

In addition to main study criteria:

• Women known to have sickle cell anaemia or thalassaemia.