Non-challenge blood glucose tests
When a plasma glucose level is found to be higher than 126 mg/dL (7.0 mmol/L) after fasting, or over 200 mg/dL (11.1 mmol/L) on any occasion, and if this is confirmed on a subsequent day, the diagnosis of GDM is made, and no further testing is required. These tests are typically performed at the first antenatal visit. They are simple to administer and inexpensive, but have a lower test performance compared to the other tests, with moderate sensitivity, low specificity and high false positive rates. Screening glucose challenge test
The screening glucose challenge test (sometimes called the OSullivan test) is performed between 24 and 28 weeks, and can be seen as a simplified version of the oral glucose tolerance test (OGTT). No previous fasting is required for this screening test, in contrast to the OGTT. The OSullivan test involves drinking a solution containing 50 grams of glucose, and measuring blood levels one hour later.If the cut-off point is set at 140 mg/dL (7.8 mmol/L), 80% of women with GDM will be detected. If this threshold for further testing is lowered to 130 mg/dL, 90% of GDM cases will be detected, but there will also be more women who will be subjected to a consequent OGTT unnecessarily. Oral glucose tolerance test
A standardized oral glucose tolerance test (OGTT) should be done in the morning after an overnight fast of between 8 and 14 hours.
It is uncertain if additional dietary advice interventions help to reduce the risk of gestational diabetes. However, data from the Nurses Health Study shows that adherence to a healthy plant-based diet is associated with lower risk for GDM.Diet and physical activity interventions designed to prevent excessive gestational weight gain reduce the rates of gestational diabetes. However, the impact of these interventions varies with the body-mass index of the person as well as with the region in which the studies were performed.Moderate-quality evidence suggest that there is a reduced risk of gestational diabetes mellitus and caesarean section with combined diet and exercise interventions during pregnancy as well as reductions in gestational weight gain, compared with standard care.It has been suggested that for women who have had gestational diabetes, support between pregnancies may lower their chances of having gestational diabetes again in future pregnancies. This support might include diet and exercise, education, and lifestyle advice. However, there is no research to show whether interventions between pregnancies lower the number of women who develop gestational diabetes again.Theoretically, smoking cessation may decrease the risk of gestational diabetes among smokers. Management
Treatment of GDM with diet and insulin reduces health problems mother and child. Treatment of GDM is also accompanied by more inductions of labour.A repeat OGTT should be carried out 6 weeks after delivery, to confirm the diabetes has disappeared. Afterwards, regular screening for type 2 diabetes is advised.Lifestyle interventions include exercise, diet advice, behavioural interventions, relaxation, self-monitoring glucose, and combined interventions.