Should HbA1C be used to screen pregnant women for undiagnosed diabetes in the first trimester? A review of the evidence.

Background: Diabetes in pregnancy is associated with miscarriage, stillbirth, congenital abnormalities, macrosomia and perinatal mortality. The demographics of the population becoming pregnant has changed (more obese and older women). More women are therefore entering pregnancy with undiagnosed diabetes.

Aim: To review the literature on HbA1c as a screening tool to identify undiagnosed diabetes in the first trimester of pregnancy.

Methods: A systematic search of the evidence was undertaken using specific search criteria from Cochrane Library, EMBASE, Medline, NICE Guidance, PROSPERO and PubMed. The initial search identified 319 papers, based on the inclusion and exclusion criteria eight papers were critically appraised.

Results: There is limited evidence on the use of HbA1c as a screening tool for undiagnosed diabetes in the literature during the first trimester of pregnancy. Although HbA1c is considered a useful test for diabetes in the non-pregnant population the hormonal and metabolic changes that occur in pregnancy mean that there are many limitations in pregnancy. Furthermore, HbA1c levels are affected by iron deficiency which is common in pregnancy.

Conclusions and recommendations: There is insufficient evidence to suggest a change in practice to include offering HbA1c screening for undiagnosed diabetes in the first trimester.