LAUSR

Abstract Background Diabetes in pregnancy is associated with miscarriage, stillbirth, congenital abnormalities, macrosomia, and perinatal mortality. The demographics of the population becoming pregnant have changed (more obese and older women). Therefore, more women are starting their pregnancy with undiagnosed diabetes. Routine measurement of glycated haemoglobin (HBA 1c ) is not undertaken as part of the first trimester blood tests in the UK. The National Clinical Lead for Diabetes in Wales requested that this testing be reviewed because of growing evidence and its recent introduction in New Zealand. We aimed to review the literature on HbA 1c as a screening tool to identify undiagnosed diabetes in the first trimester of pregnancy. Methods A systematic search of the evidence was undertaken from Jan 1 to March 31, 2017,. All study types were included. Articles not written in the English language and articles and conference proceedings were excluded. Participants included were pregnant women (all ages, all ethnicities) with undiagnosed type 2 diabetes. Participants excluded had gestational diabetes, type 1 diabetes, and type 2 diabetes diagnosed before pregnancy. Testing included was HbA 1c in the first trimester to identify type 2 diabetes. Testing excluded was HbA 1c in the second or third trimester to identify gestational diabetes. The search included papers published between Jan 1, 2009, and March 31, 2017, in the Cochrane Library, EMBASE, Medline, National Institute for Health and Care Excellence guidance, PROSPERO, and PubMed. Findings The initial search identified 319 papers; on the basis of our inclusion and exclusion criteria eight papers were critically appraised. There was limited evidence on the use of HbA 1c as a screening tool for undiagnosed diabetes during the first trimester of pregnancy. Most research assessed HbA 1c as an indicator for gestational diabetes in the third trimester. Interpretation There is insufficient evidence to suggest a change in practice to include offering HBA 1c screening for undiagnosed diabetes in the first trimester. Although HbA 1c is considered a useful test for diabetes in non-pregnant women, the hormonal and metabolic changes that occur in pregnancy mean that there are many limitations for this test in pregnancy. Furthermore, HbA 1c concentrations are affected by iron deficiency, which is common in pregnancy. Potential limitations of our study include publication bias and, in the studies themselves, selection bias. Funding None.