A Quick Synopsis of AFP's "Diagnosis and Management of Gestational Diabetes Mellitus"

Diagnosis and Management of Gestational Diabetes Mellitus
DAVID C. SERLIN, MD, and ROBERTW. LASH, MD, University of Michigan Medical School, Ann Arbor, Michigan
Am Fam Physician. 2009 Jul 1;80(1):57-62.
http://www.aafp.org/afp/2009/0701/p57.pdf

     Gestational diabetes is universally screened for in the USA. Risk factors include glycosuria, obesity, previous infant with macrosomia, first degree relative with diabetes, and history of glucose intolerance. Screening is done using a 50g nonfasting 1hr glucose challenge test at 24-28 weeks gestation. High risk patients can be screened at the first prenatal visit.  Levels should be less than 130-140 mg/dL. If positive, a 100g 3hr oral glucose tolerance test is done. The cutoff values are
95 mg/dL at fasting,
180 mg/dL at one hour,
155 mg/dL at two hours, and
140 mg/dL at three hours.
A patient who hits at least two of these cutoffs is diagnosed with gestational diabetes. Studies show that treatment of gestational diabetes will improve fetal outcomes.
     First line treatment of gestational diabetes includes dietary modification by an experienced nutritionist. If unsuccessful, insulin is considered. The starting dose is 0.7 units/kg/day.  It can be broken up by giving 2/3 in the morning and 1/3 before dinner. The morning dose should be 1/3 short acting and 2/3 NPH. The evening dose is 50/50. For patients unwilling to take insulin, glyburide or metformin are options, although metformin does cross the placenta.
     Screening these patients for anomalies (fetal well-being, estimated fetal weight, and macrosomia) includes twice weekly NST's and amniotic fluid levels in the third trimester.
     During labor, glucose should be monitored only in patients who are taking medication for gestational diabetes (qhr).  Most patients on insulin are euglycemic during labor. Early delivery reduces the risk of macrosomia, but the rates of brachial plexus injuries, hypoglycemia, and clavicle fractures remain unchanged. Postpartum, most mothers do not need continued diabetic therapy.  Half of these women will develop type 2 diabetes within 5-10 years. They should be screened every three years. Lifestyle recommendations (diet, exercise, weight loss) are also advised.