Early pregnancy HbA as the first screening test for gestational diabetes: results from three prospective cohorts.

Background: More than 90% of gestational diabetes cases are estimated to occur in low-income and middle-income countries (LMICs). Most current guidelines recommend an oral glucose tolerance test (OGTT) at 24-28 weeks of gestation. The OGTT is burdensome, especially in LMICs, resulting in a high proportion of women not being screened.