From the Guidelines
To determine the cause of postpartum prediabetes in a previously healthy individual, I recommend checking fasting plasma glucose, hemoglobin A1C, and a 75-gram oral glucose tolerance test (OGTT) as the initial steps, as suggested by the most recent guidelines 1. These tests will establish the diagnosis and severity of glucose intolerance. Additionally, the following tests should be considered:
- Thyroid function tests (TSH, free T4), as postpartum thyroiditis can affect glucose metabolism
- Complete blood count, comprehensive metabolic panel including liver enzymes, and lipid profile to assess overall metabolic health
- Testing for autoantibodies such as glutamic acid decarboxylase (GAD) antibodies and islet cell antibodies to rule out latent autoimmune diabetes
- C-peptide levels to evaluate insulin production
- Cortisol levels if Cushing's syndrome is suspected These tests are crucial because pregnancy can unmask underlying predisposition to diabetes or trigger autoimmune processes affecting pancreatic beta cells, as noted in 1 and 1. Postpartum hormonal changes, including decreasing insulin resistance after delivery, can also reveal previously undetected glucose metabolism issues, highlighting the importance of early identification and intervention to prevent progression to type 2 diabetes, as emphasized in 1 and 1. The OGTT is preferred over A1C at 4–12 weeks postpartum due to its sensitivity in detecting glucose intolerance, including both prediabetes and diabetes, as discussed in 1. Regular follow-up, potentially every 1–3 years, is necessary for individuals with a history of gestational diabetes mellitus, even if the initial postpartum tests are normal, to monitor for the development of diabetes or prediabetes, as recommended in 1.
From the Research
Labs to Check for Cause of Prediabetes Postpartum
To determine the cause of postpartum prediabetes in a previously healthy individual with no prior history of diabetes, several labs can be checked. These include:
- Fasting glucose
- Hemoglobin A1C (HbA1c)
- 2-hour oral glucose tolerance test (OGTT)
- Fasting lipid profile
- Insulin resistance tests
Rationale for Lab Tests
The rationale for these lab tests is based on studies that have shown that women with polycystic ovary syndrome (PCOS) and gestational diabetes mellitus (GDM) are at increased risk of developing prediabetes and type 2 diabetes 2, 3, 4. The 2-hour OGTT is considered the gold standard for diagnosing prediabetes and diabetes, but HbA1c and fasting glucose are also commonly used screening tests 3. However, studies have shown that HbA1c and fasting glucose may not be suitable for screening for prediabetes in women with PCOS, and that the 2-hour OGTT is a more accurate test 3.
Additional Considerations
Additional considerations when checking labs for postpartum prediabetes include:
- Assessing for other metabolic abnormalities, such as dyslipidemia and metabolic syndrome
- Evaluating for other risk factors, such as obesity and family history of diabetes
- Considering the use of electronic medical record systems to generate prompts for appropriate screening tests 2
- Educating physicians and patients about the importance of postpartum screening for glucose intolerance 5, 6
Limitations
It is worth noting that the evidence for lab tests to check for postpartum prediabetes is largely based on studies of women with PCOS and GDM, and may not be generalizable to all populations 3, 4. Additionally, the best screening strategy for postpartum glucose intolerance is still debated, and more research is needed to determine the most effective approach 6.