Cover of Screening for Gestational Diabetes Mellitus

Screening for Gestational Diabetes Mellitus

Systematic Evidence Reviews, No. 26

, MD, , MD, MPH, , DrPH, , , MPA, , BSPH, and , PhD.

Research Triangle Institute
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Structured Abstract

Context:

Gestational diabetes mellitus (GDM) has been associated with increased perinatal morbidity, maternal trauma, and an increase in operative deliveries (cesarean section and forceps or vacuum extraction). Long-term sequelae for the mother with GDM and her offspring have also been reported. A major concern is the association of GDM with fetal macrosomia and its potential for subsequent neonatal birth trauma (e.g., temporary or permanent brachial plexus injury, clavicular fracture). Although universal GDM screening has become routine practice in the United States, it is not clear that such screening has an important impact on maternal and neonatal health outcomes.

Objective:

To systematically review the evidence about the benefits and harms of screening pregnant women for gestational diabetes mellitus (GDM).

Data Sources and Study Selection:

We systematically searched MEDLINE and the Cochrane Collaboration library from 1994 through December 2001, using the Medical Subject Headings (MeSH) "diabetes, gestational" and combining this term with predefined strategies to identify diagnostic accuracy studies and randomized controlled trials (RCTs) of screening and treatment for pregnant women. We also conducted focused searches of MEDLINE from 1966 through 1994 to identify older articles of interest. We examined reference lists of textbooks, monographs and review articles; and asked experts in the field. We graded the quality of the articles according to criteria for both internal and external validity.

Data Extraction:

The first author abstracted relevant data from the included articles and entered them into a standardized form. A second reviewer checked the accuracy of the tables against the original articles. Using USPSTF criteria, we evaluated the internal and external validity and coherence of the results of each individual study and all the evidence concerning each key question.

Data Synthesis:

No well-conducted RCT provides direct evidence for the health benefits of screening for GDM. The impact of hyperglycemia on adverse maternal and fetal health outcomes is probably continuous; the magnitude of any increased risk for the large number of women at lower levels of hyperglycemia is uncertain. The evidence is unclear about the optimal screening and reference diagnostic test and cutpoint for GDM. Although insulin therapy decreases the incidence of fetal macrosomia for those women with higher levels of hyperglycemia, the magnitude of any effect on maternal and neonatal health outcomes is not clear. The evidence is insufficient to determine the magnitude of health benefit for any treatment among the large number of women with GDM at lower levels of hyperglycemia. No properly controlled prospective trials show that antepartum surveillance in patients with GDM is beneficial when compared to those with GDM but who are not monitored. As the magnitude of benefit of screening and treating GDM is uncertain, so to is the cost-effectiveness of this strategy. We found limited evidence about the potential adverse effects of screening for GDM.

Conclusion:

The evidence of screening for GDM is insufficient to determine the extent to which screening has an important impact on maternal and neonatal health outcomes. The balance of benefits versus harms remains in question, especially for the large number of women with lower degrees of hyperglycemia. There is no evidence from prospective trials that screening for GDM is a cost-effective strategy. An RCT of screening is necessary to answer the many remaining questions.