Chapter 206 Diabetes Mellitus in Pregnancy
THE CHALLENGE
Scope of the Problem: Diabetes mellitus is the most common medical complication of pregnancy, affecting 2% to 5% of patients (varying in direct proportion to the prevalence of type 2 diabetes in a given population or ethnic group). Patients who had gestational diabetes in a previous pregnancy have a 33% to 50% likelihood of recurrence in a subsequent pregnancy. Patients with type 1 diabetes are at greater risk for maternal complications (diabetic ketoacidosis, glucosuria, hyperglycemia, polyhydramnios, pre-eclampsia, pregnancy-induced hypertension, preterm labor, retinopathy, urinary tract infections, postpartum uterine atony). The offspring of women with diabetes have a 3-fold greater risk of congenital anomalies (3% to 6%) than children of mothers without diabetes (1% to 2%). Most common among these anomalies are cardiac and limb deformities. Other fetal complications include fetal demise, hydramnios, hyperbilirubinemia, hypocalcemia, hypoglycemia, macrosomia, polycythemia, prematur-ity, respiratory distress syndrome, and spontaneous abortion.
Objectives of Management: To return serum glucose levels to as close to normal as possible through a combination of diet, exercise, oral hypoglycemic agents, and insulin (for selected patients). Optimal management of diabetes begins before pregnancy. Optimal management also requires patient and family education and involvement. For the established patient with diabetes, this teaching is directed to the need for tighter control and more frequent monitoring. The woman with newly diagnosed diabetes requires general instruction about her disease and the unique aspects of diabetes during pregnancy. From the standpoint of the fetus, the goal of treatment is to reduce the likelihood of macrosomia and its consequences; neonatal hypoglycemia also may be reduced.
TACTICS
Relevant Pathophysiology: Human placental lactogen, made in abundance by the growing placenta, promotes lipolysis and decreases glucose uptake and gluconeogenesis. This anti-insulin effect is sufficient to tip borderline patients into a diabetic state or prompt readjustments in the insulin dosage used by patients with insulin-dependent diabetes. Estrogen, progesterone, and placental insulinase further complicate the management of diabetes, making diabetic ketoacidosis more common. High renal plasma flow and diffusion rates that exceed tubular reabsorption result in a physiologic glucosuria of approximately 300 mg/day. This physiologic glucosuria, combined with the poor correlation between urinary glucose and blood glucose levels, makes the urinary glucose screening useless to detect or monitor diabetes during pregnancy.
