Diabetes, Type III (Gestational Diabetes Mellitus)

Incidence of GDM approximately 5–6% of all pregnancies.

Increased in African American, Hispanic, Asian, Native American, or Pacific Islander women.

Risk factors:

• Maternal age >25 y.

• Previous delivery of macrosomic infant.

• Glucosuria.

• History of polycystic ovarian syndrome.

• Previous unexplained fetal demise.

• Previous pregnancy with GDM.

• Strong immediate family history of NIDDM or GDM.

• Obesity.

Dx: Two-step approach:

• 1.

  Fasting glucose >95 mg/dL or a glucose >130 mg/dL (identifies ~90% of women with GDM) 1 h after a 50-g OGTT.

• 2.

  If initial screening meets or exceeds threshold, perform a 100-g, 3-h diagnostic OGTT on a separate day.

Increased frequency of gestational Htn, preeclampsia, and cesarean delivery

Unlikely renal, ocular, neurologic, or orthopedic complications in GDM

Hypoglycemia if insulin is used

Fetal risk (if not controlled: Polyhydramnios or macrosomia [6 times normal])

RDS (2–3 times normal); preeclampsia, neonatal hypoglycemia, prematurity

Hyperglycemia and hypoglycemia

GDM is defined as a carbohydrate intolerance that occurs (or is first recognized) during pregnancy.

Universal screening between 24-28 wk gestation.

A glucose tolerance test is used to identify GDM. For details of the test, see the Key References.

Maternal complications with GDM are few, but the fetus is at risk.

Complications, such as fetal polyhydramnios, macrosomia (6 times normal), prematurity, birth trauma, RDS (2–3 times normal rate), neonatal hypoglycemia, or morbidity, are as common with type III diabetes (GDM) as with type I diabetes (insulin dependent).

Occurs in genetically susceptible individuals.

Pregnancy, through secretion of substances from uterus, exerts diabetogenic effects.