Am Fam Physician. 2009;80(2):173-174
Summary of Recommendations
The U.S. Preventive Services Task Force (USPSTF) concludes that the current evidence is insufficient to assess the balance of benefits and harms of screening for gestational diabetes mellitus, before or after 24 weeks' gestation (Table 1). I statement.
| Population | Pregnant women who have not previously been diagnosed with diabetes |
| Recommendation | No recommendation because of insufficient evidence |
| Grade: I | |
| Risk assessment | Women at increased risk of developing gestational diabetes include those who:
|
| Rationale for no recommendation | The current evidence is insufficient to assess the balance between the benefits and harms of screening women for gestational diabetes before or after 24 weeks' gestation. |
| Harms of screening include short-term anxiety in some women with positive screening results, and inconvenience to women and medical practices because most positive screening tests are likely false-positives. | |
| Suggestions for practice | Until there is better evidence, physicians should discuss screening for gestational diabetes with their patients and make decisions on a case-by-case basis. The discussion should include information about the uncertain benefits and harms as well as the frequency and uncertain meaning of a positive screening test result. |
| Screening tests | If a decision is made to screen for gestational diabetes:
|
| Screening intervals | Most screening is conducted between 24 and 28 weeks' gestation. There is little evidence about the value of earlier screening. |
| Other approaches to prevention | Nearly all pregnant women should be encouraged to achieve moderate weight gain based on their prepregnancy body mass index and to participate in physical activity. |
Rationale
Importance.Pregestational diabetes refers to diabetes diagnosed before pregnancy. Gestational diabetes refers to any degree of glucose intolerance with onset or first recognition during pregnancy. Pregnant women with pregestational diabetes are at increased risk of multiple complications affecting the mother and the fetus. The degree to which pregnant women with gestational diabetes are at increased risk of maternal or fetal complications is less certain.
Detection.Several different methods are used to screen for gestational diabetes; many women with positive screening test results do not meet current diagnostic criteria for gestational diabetes.
Benefits of Detection and Early Treatment.Screening before 24 weeks' gestation: The evidence is poor to determine whether there are benefits to screening women at this time in pregnancy.
Screening after 24 weeks' gestation: Although screening and early treatment of gestational diabetes reduces macrosomia, and although one trial suggests the possibility of other health benefits, the overall evidence is poor to determine whether maternal or fetal complications are reduced by screening.
Harms of Detection and Early Treatment.There is fair evidence that short-term anxiety occurs in some women with positive screening results; longer-term psychological or other harms have not been documented. The majority of positive screening test results are probably false-positives. Consequently, it is likely that many women and medical practices are being inconvenienced unnecessarily by screening.
USPSTF Assessment.The USPSTF concludes that the current evidence is insufficient to assess the balance between the benefits and harms of screening women for gestational diabetes before or after 24 weeks' gestation.
Clinical Considerations
Patient Population. This recommendation concerns pregnant women who have not previously been diagnosed with diabetes.
Suggestions for Practice. Until there is better evidence, physicians should discuss screening for gestational diabetes with their patients and make case-by-case decisions. Discussions should include information about the uncertainty of benefits and harms as well as the frequency of positive screening test results.
Assessment of Risk. Women who are obese, older than 25 years, or of certain ethnic groups (Hispanic, American Indian, Asian, or black), or who have a family history of diabetes or a history of previous gestational diabetes are at increased risk of developing gestational diabetes.
Screening Tests. In the United States, the most common screening test is an initial 50-g one-hour glucose challenge test. If the result of the glucose challenge test is abnormal, variably defined as greater than 130 or 140 mg per dL (7.2 or 7.8 mmol per L), the patient undergoes a 100-g three-hour oral glucose tolerance test. Two or more abnormal values on the oral glucose tolerance test are considered diagnostic for gestational diabetes.
Time of Screening. Most screening is conducted between 24 and 28 weeks' gestation. There is little evidence about the value of earlier screening.
Treatment. Treatment usually includes recommendations for physical activity and dietary modification. In addition, treatment sometimes includes medication (insulin or oral hypoglycemic agents), support from diabetes educators and nutritionists, and increased surveillance in prenatal care. The extent to which these interventions improve health outcomes is uncertain.
Other Approaches to Prevention. Nearly all pregnant women should be encouraged to achieve moderate weight gain based on their prepregnancy body mass index and to participate in physical activity.