Dietary therapy for gestational diabetes: How long is long enough?

Objective: To determine the length of time required for dietary therapy alone to effect good glycemic control and whether the need for insulin treatment can be predicted at diagnosis of gestational diabetes mellitus (GDM). Methods: Women with GDM were treated with dietary therapy for 4 weeks. Each measured her blood glucose using a memory-based reflectance glucometer, and those in poor glycemic control (mean glucose exceeding 105 mg/dL) after 4 weeks of dietary therapy were prescribed insulin. Women were stratified by fasting plasma glucose value of 3-hour glucose tolerance tests (GTTs). Results: Women with fasting glucose at or below 95 mg/dL were significantly more likely to achieve good glycemic control after 2 weeks of dietary therapy than were those with values above 95 mg/dL whose control did not improve during the study. Receiver operating characteristic (ROC) analysis determined that fasting values of GTT between 91 and 95 mg/dL best predicted that insulin would be needed for good glycemic control. Conclusion: Women with GDM should be prescribed dietary therapy alone for at least 2 weeks before they are prescribed insulin. In those with fasting glucose above 95 mg/dL, insulin may be prescribed after 1 week of dietary therapy, or at diagnosis.