Gestational diabetes mellitus

What it is

Gestational diabetes is diabetes diagnosed in the second or third trimester of pregnancy that was not clearly overt diabetes prior to gestation. In the classification used here it is type 4. Type 1 is immune mediated, type 2 is adult onset due to insulin resistance and deficiency, and type 3 is the specific types: a genetic defect of the beta cell, of insulin action, or of the exocrine pancreas. Pregnancy itself works against insulin: the anti-insulin hormones are estrogen, progesterone, prolactin, cortisol and human placental lactogen. It complicates around 1 in 40 pregnancies.

Causes and risk

Screen early, rather than waiting, in a woman with:

• Body mass index over 30
• Low LDH, high triglyceride
• Asian ethnic origin, or family hx
• Previous macrosomia of 4.5 kg, previous gestational diabetes, previous stillbirth or previous intra uterine fetal death
• PCOS
• Previous unexplained polyhydramnios
• Cardiovascular disease
• HbA1c over 5.7

Another list of risk factors runs: a BMI over 30, a previous macrosomic baby weighing 4.5 kg or above, previous gestational diabetes, a first-degree relative with diabetes, and family origin with a high prevalence of diabetes, named as South Asian, black Caribbean and Middle Eastern.