Pregestational (type 1 and type 2) diabetes mellitus in pregnancy
Pregestational diabetes is type 1 or type 2 diabetes mellitus present before conception, affecting about 1 to 2 percent of pregnancies. The diagnosis rests on a preexisting diagnosis or first-trimester glucose values meeting standard diabetes criteria. First-line treatment is insulin, titrated to a fasting glucose below 95 mg per deciliter, because it does not cross the placenta.
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What this article covers
- Overview
Definition: pregestational diabetes is type 1 or type 2 diabetes mellitus present before conception, as opposed to gestational diabetes mellitus (GDM), which arises during pregnancy.
- Epidemiology
Prevalence: pregestational diabetes complicates about 1 to 2 percent of pregnancies, less common than gestational diabetes.
- Risk factors
Overweight or obesity: body mass index above 25 raises the odds of unmasked type 2 diabetes.
- Pathophysiology
Placental hormone drive: human placental lactogen, progesterone, cortisol, and growth hormone rise across gestation and antagonize maternal insulin action.
- Clinical features
Time course: disease activity is mostly silent to the patient; the picture is defined by glucose trends and end-organ findings rather than symptoms.
- Differential diagnosis
Gestational diabetes mellitus: carbohydrate intolerance first recognized at 24 to 28 weeks, without first-trimester hyperglycemia and without the added malformation risk.
- Diagnosis
What establishes the diagnosis: pregestational diabetes is diagnosed when a patient enters pregnancy with an established diagnosis of type 1 or type 2 diabetes, or when hyperglycemia meeting standard…
- Management
First, start or continue insulin, individualized basal-bolus (basal detemir or neutral protamine Hagedorn, bolus lispro or aspart with meals), near 0.7 to 1 unit/kg/day split basal and bolus, as the…
- Complications
Maternal diabetic ketoacidosis (DKA), or hyperosmolar hyperglycemic state (HHS) in type 2 disease: acute decompensation at any gestational age.
- Prognosis
Periconceptional and early-pregnancy control is the dominant predictor of malformation risk: the closer HbA1c is to nondiabetic values, the lower the risk, while a first-trimester HbA1c above 8 percent should prompt anomaly workup.
- Prevention
Preconception counseling and glycemic optimization: target HbA1c under 6.5 percent, ideally near 6 percent, before conception.
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Related articles
- Gestational diabetes mellitus
Gestational diabetes mellitus is carbohydrate intolerance first identified in the second or third trimester, diagnosed with a 50-g glucose challenge test followed by a confirmatory 100-g oral glucose tolerance test. Insulin is first-line pharmacologic therapy when glycemic targets are not met with diet and exercise, and untreated hyperglycemia drives fetal macrosomia, shoulder dystocia, neonatal hypoglycemia, and later maternal type 2 diabetes.
- Preeclampsia
New-onset hypertension after 20 weeks of gestation with proteinuria or end-organ dysfunction, driven by abnormal placental spiral artery remodeling and widespread endothelial dysfunction. Eclampsia is preeclampsia complicated by seizures; magnesium sulfate treats and prevents seizures, and prompt delivery is the only definitive cure for both.
- Diabetic ketoacidosis
Diabetic ketoacidosis is a life-threatening hyperglycemic crisis of near-absolute insulin deficiency, most common in type 1 diabetes, producing an anion-gap ketoacidosis from unrestrained lipolysis and osmotic diuresis from severe hyperglycemia. It is diagnosed by hyperglycemia, ketonemia, and an anion-gap metabolic acidosis, and treated with intravenous isotonic saline, an intravenous regular insulin bolus and infusion, and aggressive potassium repletion guided by frequent electrolyte monitoring.
- Type 1 diabetes mellitus
Type 1 diabetes mellitus is an insulin-deficient state from autoimmune (type 1A) or idiopathic (type 1B) destruction of pancreatic beta cells, presenting with hyperglycemia that can range from mild to life-threatening diabetic ketoacidosis. Diagnosis combines standard glycemic criteria with autoantibody testing (GAD65, IA-2), and lifelong insulin therapy, generally as a basal-bolus regimen, is required from diagnosis, with self-monitoring or continuous glucose monitoring to guide dosing.
- Type 2 diabetes mellitus
Type 2 diabetes is hyperglycemia from insulin resistance with progressive relative insulin deficiency, diagnosed by a hemoglobin A1c of 6.5% or higher, a fasting glucose of 126 mg/dL or higher, or a 2-hour oral glucose tolerance test value of 200 mg/dL or higher. First-line treatment is lifestyle modification plus metformin, with an SGLT2 inhibitor or GLP-1 receptor agonist added early for patients with atherosclerotic disease, kidney disease, or heart failure.