Gestational diabetes mellitus (GDM) develops during pregnancy and is usually diagnosed at 24 to 28 weeks of gestation on the basis of elevated plasma glucose levels on glucose tolerance testing.
Goal of therapy is to achieve maternal glucose levels that are as close to normal as possible in order to avoid fetal macrosomia and complications.
Initial therapy for GDM is usually dietary modification. Insulin is started when acceptable glucose levels cannot be maintained with diet alone.
Maternal postnatal testing for diabetes or impaired glucose tolerance is performed at 4 to 6 weeks following delivery.
The risk for recurrence of GDM in subsequent pregnancies or progression to type 2 diabetes is high.
Gestational diabetes mellitus (GDM) was previously defined as any degree of glucose intolerance with onset or first recognition during pregnancy. This definition included a population of women with preexisting type 2 diabetes, so the definition has been modified to indicate that the diagnosis is after the first trimester of pregnancy. It is usually recognized at 24 to 28 weeks of gestation on the basis of abnormal glucose tolerance testing. The criteria for diagnosing GDM remain controversial.
History and exam
Key diagnostic factors
- presence of risk factors
- abnormal oral glucose tolerance test
Other diagnostic factors
- fetal macrosomia
- advanced maternal age (>40 years)
- elevated BMI
- polycystic ovarian syndrome (PCOS)
- nonwhite ancestry
- family history of diabetes mellitus
- previous gestational diabetes
- increased amniotic fluid volume
1st investigations to order
- one-step test option: 75-g oral glucose tolerance test (OGTT)
- two-step test option: 1-hour 50-g glucose load test (GLT), followed by 3-hour 100-g OGTT
Investigations to consider
- fasting blood (plasma) glucose
- random blood (plasma) glucose
- Type 1 diabetes
- Type 2 diabetes
- Standards of medical care in diabetes - 2022
- Managing diabetes and hyperglycaemia during labour and birth
Diabetes that develops in pregnancy (gestational diabetes)
Diabetes type 2: what treatments work?More Patient leaflets
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