Response to Dashora et al.

We thank Dashora et al. (1) for their comments regarding our study (2). Their observations corroborate our findings about the validity of using a 2-h 75-g OGTT in pregnancy to detect gestational diabetes mellitus (GDM).

In their study, the 2-h 75-g OGTT was done at booking and, if normal, was repeated two or three times at 2-month intervals. Using World Health Organization (WHO) criteria, they found a 21.3% prevalence of GDM, with over 88% of cases being diagnosed before the 7th month of pregnancy. This high prevalence of diagnosis may reflect a truly higher prevalence or may in part be the result of their more intensive screening policy. They concluded that early and multiple screening is important and recommended more aggressive screening in Oman and other settings with a high prevalence of diabetes.

In our study, the prevalence of GDM was 7.2% by WHO criteria. With this prevalence, population-attributable fractions for adverse pregnancy outcomes associated with a diagnosis of GDM were small (<8%). Assuming that the relative risks we found are applicable to those with GDM in Oman, diagnosed as described, and considering the prevalence of GDM (21.3%) found by Dashora et al., population-attributable fractions would be 12% for macrosomia, 23% for preeclampsia, and 13% for perinatal death.

When establishing the intensity of GDM screening, other factors need to be taken into account, especially because evidence to support GDM screening is largely based on observational studies and consensus. An important factor is the effectiveness of alternative strategies and competing priorities for prevention of perinatal morbimortality. Such evaluation requires modern cost-effectiveness analyses.

Given the uncertainties regarding these issues in Brazil, the second meeting of Diabetes in Pregnancy held last April in Porto Alegre, Brazil, recommended the following screening protocol (Fig. 1): 1) to screen all women at booking with fasting plasma glucose (FPG) using, as a cut point, a value of 85 or 90 mg/dl, depending on the priority established for GDM in the local setting; 2) at weeks 20–24, to apply a diagnostic 2-h 75-g oral glucose tolerance test to those judged to be positive, with a diagnosis of GDM to be made if FPG is ≥110 mg/dl or 2-h plasma glucose is ≥140 mg/dl; 3) after week 20, to screen previously negative women again; 4) to obtain immediate diagnostic confirmation of a screening FPG ≥110 mg/dl, at any moment.

Until more data are available on the cost-effectiveness of various screening strategies, detection of GDM must be based on local guidelines that take into account available resources and health care priorities.