One-third of patients with gestational diabetes mellitus (GDM) require hypoglycemic agents. There is a subset of patients who control their postprandial values with diet, yet they have persistent fasting hyperglycemia requiring bedtime hypoglycemic agents (GDMHS). As fasting hyperglycemia is an independent risk factor for adverse pregnancy outcomes, we aimed to identify risk factors to predict (and subsequently counsel) GDM patients with a risk of isolated fasting hyperglycemia requiring treatment with bedtime hypoglycemic agents.
This was an IRB-approved retrospective cohort study of patients diagnosed with GDM after 24 weeks from 2016 to 2020. Patients monitored glucose four times daily (fasting and 2 hours postprandial); fasting hyperglycemia was defined as more than 50% fasting values greater than 90 mg/dL. Patients completely controlled with diet (GDMA1) were compared to those with GDMHS. A multivariate analysis assessed whether age, body mass index (BMI), fasting glucose tolerance test (GTT) value, HbA1c at diagnosis, history of polycystic ovarian syndrome or previous GDM, Asian race, or family history of diabetes predicted isolated fasting hyperglycemia.
Four hundred five patients had GDM. 57% had GDMA1, and 28% had GDMHS. Compared to GDMA1, patients with GDMHS were older, had higher BMI, higher fasting GTT value, higher HbA1c, and higher incidence of previous GDM or family history of diabetes. After adjusting for confounders, higher HbA1c at GDM diagnosis (odds ratio [OR] 3.55), older age (OR 1.08), and higher fasting GTT value (OR 1.06) were significantly associated with an increased probability of persistent fasting hyperglycemia. Asian race was associated with decreased probability of fasting hyperglycemia but was confounded by lower fasting GTT and lower BMI.
Our data suggest that elevated HbA1c, higher fasting GTT value, and older age may predict persistent isolated fasting hyperglycemia in GDM patients who are otherwise controlled with diet. These data can be used to educate and counsel patients to alleviate frustration encountered with persistent fasting hyperglycemia despite postprandial diet control.