Miscarriage
Poorly controlled blood glucose, especially during the first trimester, significantly increases the risk of miscarriage. Miscarriage rates are higher in diabetic pregnancies, particularly if glucose levels are not well-managed early on.
Hypoglycemia
Tight targets, first-trimester nausea, and the rising insulin sensitivity of early pregnancy make severe maternal hypoglycemia most common between about 8 and 16 weeks, and hypoglycemia unawareness is frequent. Insulin requirements then climb steadily from the second trimester as placental hormones drive insulin resistance, often doubling by term, and fall abruptly once the placenta is delivered.
Preeclampsia and Superimposed Preeclampsia
Women with diabetes are at a higher risk of developing preeclampsia, a condition characterized by high blood pressure and potential organ damage. Preeclampsia worsens blood flow to the placenta, which can lead to fetal distress, placental abruption, or stillbirth. Superimposed preeclampsia in diabetic women presents an even greater risk due to impaired blood vessel function and oxidative stress. Pre-existing diabetes raises the risk of preeclampsia to roughly 15% to 20%, which is why ACOG recommends low-dose aspirin (81 mg daily) from 12 to 16 weeks of gestation until delivery for these women.
Diabetic Nephropathy
This form of kidney damage, resulting from long-term diabetes, can worsen during pregnancy. It leads to proteinuria (protein in the urine), increased blood pressure, and deteriorating kidney function, all of which elevate the risk of preterm birth and fetal growth restriction. Diabetic retinopathy can also progress during pregnancy, so a dilated eye examination is recommended before conception or in the first trimester and repeated as needed.
Diabetic Ketoacidosis (DKA)
DKA is a critical, life-threatening complication characterized by hyperglycemia, ketosis, anion-gap metabolic acidosis, dehydration, and electrolyte imbalances. In pregnancy it develops faster and at lower glucose levels than outside pregnancy: the glucose is often only modestly raised and is below 200 mg/dL (so-called euglycemic DKA) in a meaningful minority of cases, because the fetoplacental unit consumes glucose while placental hormones accelerate lipolysis and ketogenesis, and the lower resting bicarbonate and PaCO2 of pregnancy leave less buffering reserve. Common precipitants are vomiting, infection, missed insulin, beta-agonist tocolytics such as terbutaline, and antenatal corticosteroids given for fetal lung maturity (expect insulin requirements to rise for 24 to 72 hours after betamethasone). DKA complicates roughly 1% to 3% of diabetic pregnancies, and fetal loss has been reported in about 10% to 35% of episodes, so a pregnant woman with diabetes who is vomiting or unwell needs ketones checked even when her glucose looks reassuring. Treatment follows the non-pregnant protocol (aggressive isotonic fluids, intravenous insulin, potassium replacement, treating the precipitant) with left uterine displacement, supplemental oxygen, and continuous fetal monitoring once the fetus is viable; fetal heart rate abnormalities usually resolve as the mother is corrected, so emergency delivery during the acidosis is generally avoided.
Cardiovascular Complications
Diabetic pregnancies increase the risk of cardiovascular disease. Conditions such as hypertension, heart failure, and even heart attacks are more likely when blood glucose levels are poorly controlled.
