Initial assessment
Assessment of hyperglycaemia in pregnancy begins at the first antenatal visit, with universal screening using fasting plasma glucose. Values below ninety-two milligrams per decilitre are considered normal at this stage. In these cases, the diagnosis of gestational diabetes is not established, and the pregnant woman should undergo a seventy-five gram oral glucose tolerance test between twenty-four and twenty-eight weeks, the recommended period for formal diagnosis.
Early diagnosis
Fasting plasma glucose values between ninety-two and one hundred and twenty-five milligrams per decilitre define early gestational diabetes. In the absence of metabolic risk factors, confirmation with a second measurement may be considered, reducing the risk of overdiagnosis. Values equal to or above one hundred and twenty-six milligrams per decilitre, random plasma glucose equal to or above two hundred milligrams per decilitre in the presence of symptoms, or glycated haemoglobin equal to or above six point five percent are compatible with diabetes in pregnancy, often corresponding to previously undiagnosed pre-existing diabetes, and should prompt hospital referral.
Diagnosis in the second trimester
Between twenty-four and twenty-eight weeks, the oral glucose tolerance test is the reference examination. The diagnosis of gestational diabetes is established when at least one value is abnormal: fasting plasma glucose equal to or above ninety-two milligrams per decilitre, one-hour glucose equal to or above one hundred and eighty milligrams per decilitre, or two-hour glucose equal to or above one hundred and fifty-three milligrams per decilitre. In the absence of abnormal values, the pregnant woman is considered normoglycaemic. The distinction between gestational diabetes and diabetes in pregnancy has therapeutic and obstetric implications, particularly regarding the risk of insulin therapy and maternal-fetal surveillance.
Postpartum reassessment
After delivery, gestational diabetes is an important marker of future risk of type 2 diabetes. Between the sixth and eighth postpartum week, an oral glucose tolerance test or, at minimum, fasting plasma glucose is recommended, applying the criteria used in the general population. Fasting values below one hundred milligrams per decilitre and two-hour values below one hundred and forty milligrams per decilitre define normality. Fasting plasma glucose between one hundred and one hundred and twenty-five milligrams per decilitre or two-hour glucose between one hundred and forty and one hundred and ninety-nine milligrams per decilitre defines prediabetes. Values equal to or above one hundred and twenty-six milligrams per decilitre fasting or two hundred milligrams per decilitre at two hours confirm diabetes. In women previously classified as having diabetes in pregnancy, this reassessment aims to confirm the definitive diagnosis of type 2 diabetes.
Follow-up and surveillance
Long-term metabolic surveillance should be structured. Even after postpartum normalization, repeat screening every one to three years is recommended, especially in the presence of additional risk factors. In prediabetes, interventions targeting weight, physical activity and dietary pattern reduce progression to diabetes and improve cardiovascular risk. When the diagnosis of diabetes mellitus is confirmed, the woman should enter continuous follow-up with control of risk factors and surveillance for complications, considering the impact of obstetric history and the risk of recurrence in future pregnancies.
