Medical complications of diabetes and pregnancy include those specifically related to diabetes and an increased risk for pre-eclampsia.
Diabetic nephropathy complicates approximately 5% of pregnancies in women with pre-existing diabetes. Most affected pregnancies are in women with type 1 diabetes. Disease progression is characterized by hypertension and deteriorating glomerular filtrations rate. Progression of diabetic nephropathy can be attenuated by aggressive treatment of hypertension and intensive glycemic control.[33
] Some women with diabetic nephropathy display the expected increase in glomerular filtration noted in normal pregnancy; others do not experience a significant increase. Women with overt diabetic nephropathy experience increased proteinuria in pregnancy. The greater the proteinuria at onset of pregnancy, the greater is its increase during the pregnancy. Protein excretion can double or triple in the third trimester compared with the first, and can confuse the diagnosis of pre-eclampsia. Approximately 50% of women deliver preterm iatrogenically because of maternal or fetal indications, 15% have fetuses with intrauterine growth restriction (IUGR), and pre-eclampsia occurs in approximately 50%. Women with a prepregnancy creatinine of greater than 1.5 mg/ dL have the highest perinatal complication rate.[34
] Antihypertensive therapy delays progression of diabetic nephropathy. Angiotensin-converting enzyme inhibitors or angiotensin receptor blockers have clearly been shown to be superior in slowing progression of microalbuminuria in women with diabetes with and without hypertension.[35
] Unfortunately, these medications are teratogenic throughout pregnancy and cannot be used during pregnancy.[36
Diabetic retinopathy, still one of the leading causes of blindness and visual disability in the world, is most often associated with long-standing type 1 diabetes. Evidence shows that diabetic retinopathy advances with pregnancy, at least for the short term.[37
] However, pregnancy does not seem to have long-term consequences on diabetic retinopathy. Controversy exists over whether the microvascular changes in the eye are from pregnancy itself or the rapid improvement of glycemic control that occurs in some women when pregnancy is discovered. Factors associated with progression of diabetic retinopathy in pregnancy are the duration of type 1 diabetes, the presence of chronic hypertension or pre-eclampsia, the degree of hyperglycemia, poor glycemic control at conception, and the stage of disease at onset of pregnancy.[38
] Fluid retention, vasodilation, and increased blood flow in pregnancy are believed to accelerate the loss of autoregulatory function of the retinal capillary bed. Diabetic retinopathy can be classified as background, preproliferative, or proliferative, depending on progression. Progression from nonproliferative to proliferative retinopathy ranges from 6% to 30% depending on severity.[39
] The treatment of diabetic retinopathy using laser photocoagulation is as effective in pregnancy as outside of pregnancy and should not be delayed.
Diabetic neuropathy in pregnancy has not been well studied. A short-term increase in distal symmetric polyneuropathy may occur in association with pregnancy, but at least in one study the increase appeared to be transient.[40
] Women with diabetic gastroparesis may experience more protracted nausea and vomiting of pregnancy. This complication should be considered and treated. Coronary artery disease is not commonly seen in pregnant women with diabetes. Information related to the incidence of coronary artery disease in pregnant women with diabetes is sparse and only case reports exist in the literature. Data are insufficient to extrapolate recommendations. However, women with pre-existing angina or myocardial infarction should generally not be encouraged to become pregnant, particularly if they have diminished cardiac function.
Diabetic ketoacidosis (DKA) is an uncommon occurrence in treatment-compliant women with type 1 diabetes, despite the increased risk for this complication associated with the ketogenesis of normal pregnancy. However, DKA is a common complication in undiagnosed diabetes. Any pregnant woman with vomiting or dehydration and blood sugars greater than 200 mg/dL should have electrolytes, plasma bicarbonate, and serum acetone levels measured to confirm DKA diagnosis. Arterial blood gasses should be obtained if the plasma bicarbonate is low and acetone is present. The precipitant of DKA is often infection, which should be diagnosed and treated promptly. Resolution of DKA can be slower in pregnancy. DKA is often associated with a non-reassuring fetal heart rate tracing, which in most cases resolves once the metabolic acidosis improves. However, despite improved management, DKA remains an important cause of fetal loss in diabetic pregnancies.[41