Based on its review, the task force recommended screening for gestational diabetes in asymptomatic pregnant patients at 24 weeks gestation or later. This is a “B” recommendation, and applies to pregnant people who have not previously been diagnosed with type 1 or type 2 diabetes and who do not have signs or symptoms of the condition.
The USPSTF also stated that there was insufficient evidence to assess the balance of benefits and harms of screening for gestational diabetes in asymptomatic pregnant patients before 24 weeks gestation — an “I” statement.
“Clinicians can help pregnant people and their babies stay healthy by screening for gestational diabetes at or after 24 weeks of pregnancy,” said task force member Chien-Wen Tseng, M.D., M.P.H., M.S.E.E., associate research director in the Department of Family Medicine and Community Health at the University of Hawaii John A. Burns School of Medicine, in a news release. “Screening is safe and can accurately identify gestational diabetes so that it can be treated to help reduce the likelihood of large babies, trauma during birth, cesarean sections and other serious health problems.”
The CDC estimates that between 2% and 10% of pregnancies in the United States are affected by gestational diabetes each year. The condition carries both short-term and long-term risks for patients and their infants. Babies born to patients with gestational diabetes are at increased risk of very large birth weight, premature birth, low blood sugar and development of type 2 diabetes, while about half of all patients who experience gestational diabetes go on to develop type 2 diabetes later in life.
Recent evidence also suggests that the rate of the gestational diabetes in the United States is increasing. A study published Aug. 17 in JAMA found that in individuals giving birth to a single child for the first time, gestational diabetes rates increased across all age groups and among all race and ethnicity subgroups between 2011 and 2019.
The final recommendation statement is consistent with the task force’s previous recommendation statement on the topic, published in January 2014, which also recommended screening for gestational diabetes after 24 weeks gestation but found insufficient evidence to assess the balance of benefits and harms of earlier screening. The AAFP supported the 2014 recommendation.
To update the previous recommendation, the task force commissioned a systematic review of the evidence to evaluate the accuracy, benefits and harms of screening for gestational diabetes and the benefits and harms of treatment for the pregnant patient and infant. Data sources included studies published between 2010 and May 2021, as well as trial data from ClinicalTrials.gov, reference lists of primary studies and systematic reviews, with additional surveillance of the literature conducted through June 2021.
A total of 20 trials and 87 observational studies were included in the evidence review. Among the new evidence were seven studies that examined the harms associated with undertaking screening for or a diagnosis of gestational diabetes, and seven trials on the comparative effectiveness of different screening strategies.
The review found limited evidence on the benefits of screening vs. no screening. While screening tests were considered “reasonably accurate” for identifying patients who do not need to proceed to a diagnostic test as part of a two-step strategy, they were also considered “likely inadequate” to diagnose gestational diabetes.
While diagnosis of gestational diabetes using more inclusive criteria was likely to identify additional patients at increased risk of adverse maternal and fetal/neonatal outcomes, the evidence did not indicate any short-term benefit from using one-step screening vs. two-step screening.
With regard to screening strategies on health outcomes, results from five trials indicated that screening with International Association of Diabetes and Pregnancy Study Group criteria identified more cases of gestational diabetes than screening with Carpenter and Coustan criteria. Overall, one-step vs. two-step screening was not associated with differences in any of several health outcomes, including preeclampsia, gestational hypertension, preterm delivery, large for gestational age infant, birth injury, neonatal hypoglycemia or perinatal mortality.
For pregnant patients, treatment for gestational diabetes at or after 24 weeks gestation was associated with decreased risk of primary cesarean deliveries and preterm deliveries, although findings for the latter outcome were not statistically significant. Treatment was not associated with reduced risk of preeclampsia, gestational hypertension, total cesarean deliveries, emergency cesarean deliveries, induction of labor or maternal birth trauma.
For fetal/neonatal outcomes, treatment at 24 weeks gestation or later was associated with reduced risk of shoulder dystocia, macrosomia, large for gestational age infant, birth injury and neonatal ICU admissions, but no association was found for mortality, respiratory distress syndrome, hypoglycemia or hyperbilirubinemia.
The task force also noted several gaps in the existing evidence and called for more research in several areas, including studies that would
A draft version of the recommendation statement was posted for public comment on the USPSTF website from Feb. 16 through March 15, 2021.
In response to several requests that the recommendation include guidance on which screening test should be used, the task force found that several screening tests (such as the oral glucose challenge test, oral glucose tolerance test and fasting plasma glucose) and strategies can accurately diagnose gestational diabetes, and as such the task force did not recommend any specific test.
Several commenters requested that the USPSTF recommend screening only pregnant patients at increased risk for gestational diabetes to minimize false-positive test results and unnecessary labeling of lower-risk patients, but the task force found only limited data on risk-based screening strategies.
The task force received a number of comments on the potential benefit of screening before 24 weeks gestation, or screening later in pregnancy. The USPSTF stated that it found limited data on the benefits and harms of screening before 24 weeks gestation, and that it is calling for more evidence in this period of pregnancy. The USPSTF also stated that while the recommendation does not preclude later screening, other groups recommend screening between 24 weeks and 28 weeks, and the Practice Considerations section was updated to provide clarifying information.
Finally, several respondents asked the task force to include guidance on screening for preexisting diabetes and prediabetes in pregnant patients. While the task force recognized the difficulty in distinguishing between gestational diabetes and previously undiagnosed diabetes, it stated that the detection and management of preexisting diabetes during pregnancy is beyond the scope of the recommendation. It also stated that health care professionals should use their clinical judgment to determine whether screening is appropriate for individual patients.
The USPSTF has published several other recommendations related to pregnancy and the prevention of gestational diabetes. These include recommendations on
The AAFP’s Commission on Health of the Public and Science plans to review the task force’s final recommendation statement, final evidence summary and evidence review, and will then determine the Academy’s stance on the recommendation.