This is most commonly fast-acting insulin given just before eating to blunt glucose rises after meals. Care needs to be taken to avoid low blood sugar levels due to excessive insulin. Insulin therapy can be normal or very tight; more injections can result in better control but requires more effort, and there is no consensus that it has large benefits. A 2016 Cochrane review concluded that quality evidence is not yet available to determine the best blood sugar range for improving health for pregnant women with GDM and their babies.There is some evidence that certain medications by mouth might be safe in pregnancy, or at least, are less dangerous to the developing fetus than poorly controlled diabetes. When comparing which diabetes tablets (medication by mouth) work best and are safest, there is not enough quality research to support one medication over another. The medication metformin is better than glyburide. If blood glucose cannot be adequately controlled with a single agent, the combination of metformin and insulin may be better than insulin alone. Another review found good short term safety for both the mother and baby with metformin but unclear long term safety.People may prefer metformin by mouth to insulin injections. Treatment of polycystic ovarian syndrome with metformin during pregnancy has been noted to decrease GDM levels.Almost half of the women did not reach sufficient control with metformin alone and needed supplemental therapy with insulin; compared to those treated with insulin alone, they required less insulin, and they gained less weight.
Type T: prior kidney transplant.An early age of onset or long-standing disease comes with greater risks, hence the first three subtypes.Two other sets of criteria are available for diagnosis of gestational diabetes, both based on blood-sugar levels.Criteria for diagnosis of gestational diabetes, using the 100 gram Glucose Tolerance Test, according to Carpenter and Coustan:
Fasting 95 mg/dl
1 hour 180 mg/dl
2 hours 155 mg/dl
3 hours 140 mg/dlCriteria for diagnosis of gestational diabetes according to National Diabetes Data Group:
Fasting 105 mg/dl
1 hour 190 mg/dl
2 hours 165 mg/dl
3 hours 145 mg/dl

Risk factors
Classical risk factors for developing gestational diabetes are:
Polycystic ovary syndrome
A previous diagnosis of gestational diabetes or prediabetes, impaired glucose tolerance, or impaired fasting glycaemia
A family history revealing a first-degree relative with type 2 diabetes
Maternal age – a womans risk factor increases as she gets older (especially for women over 35 years of age). Paternal age – one study found that a fathers age over 55 years was associated with GD
Ethnicity (those with higher risk factors include African-Americans, Afro-Caribbeans, Native Americans, Hispanics, Pacific Islanders, and people originating from South Asia)
Being overweight, obese or severely obese increases the risk by a factor 2.1, 3.6 and 8.6, respectively. A previous pregnancy which resulted in a child with a macrosomia (high birth weight: >90th centile or >4000 g (8 lbs 12.8 oz))
Previous poor obstetric history
Other genetic risk factors: There are at least 10 genes where certain polymorphism are associated with an increased risk of gestational diabetes, most notably TCF7L2.In addition to this, statistics show a double risk of GDM in smokers.