The American Diabetes Association (ADA) has recommended selective screening for gestational diabetes mellitus (GDM) (1). Pregnant women aged <25 years, who have normal body weight, no family history of diabetes, and are not members of an ethnic/racial group with a high prevalence of diabetes, are regarded as a low-risk group for GDM and need not be screened. The effect of selective screening guidelines has been investigated in Caucasian populations using a 100-g 3-h oral glucose tolerance test (OGTT) (2,3). We report here the effect of the selective screening protocol.
A total of 9,471 pregnant women in Tianjin, China, took part in a universal screening program from December 1998 to December 1999. The screening test consisted of a 50-g 1-h glucose test and was carried out at 26- to 30-weeks’ gestation. A total of 888 (9.4%) women had a glucose reading >7.8 mmol/l, of whom 701 undertook a further 75-g 2-h OGTT using the WHO diagnostic criteria for GDM (baseline: ≥7.0 mmol/l; 2-h: ≥7.8 mmol/l) (4). A total of 171 women were confirmed to have GDM (prevalence 1.8%).
Age, prepregnancy BMI, and family history of diabetes were risk factors for GDM in this cohort. The prevalence of overweight (BMI ≥25 kg/m2) was low (10%), and family history of diabetes was uncommon (8%). Furthermore, the one-child policy has resulted in a cohort of 98% (9,240/9,471) of nulliparas. Twenty-eight percent of women were <25 years of age.
The application of the ADA selective screening guideline in this study would exclude 24% (2,248/9,469) of women from the screening test. An estimated 12% of women with confirmed GDM under the WHO criteria would otherwise have been denied the opportunity for early detection. These findings differ substantially from reports using the ADA recommendations: exclusion of 10% of women in the screening and oversight of 4% of GDM women (3).
We adopted a similar, although slightly later, approach to the initial screening (26- to 30- vs. 24- to 28-weeks’ gestation) (1). The WHO diagnostic criteria have been shown to give a higher estimation of GDM prevalence (5,6) in comparison with the ADA criteria. However, the prevalence of GDM in our study population was low. As our subjects are deemed a high-risk group (of Asian backgrounds) under the ADA selective screening guidelines, the lack of other risk factors is an important determinant of GDM prevalence. The greater proportion of Chinese women with GDM who would fail to be identified using selective screening, compared with the proportion shown in other studies, is unlikely to be explained by either the delay in screening or the use of the WHO criteria. The low frequency of risk factors for GDM in this cohort was associated with a low prevalence of GDM. However, young and lean women were not immune from the development of GDM. We conclude that if selective screening is to be considered in this population, different age and BMI cutoff points are required, and other risk factors for GDM (such as stature) may need to be considered for inclusion in any revised selective screening recommendation.
Address correspondence to Bridget Hsu-Hage, Department of Rural Health, Faculty of Medicine, University of Melbourne, PO Box 6500, Shepparton, Victoria 3632, Australia. E-mail: email@example.com.