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Gestational Diabetes Screening
TAKE-HOME MESSAGE
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This RCT compared two screening methods for gestational diabetes, a 1-step protocol using the 2-hour glucose tolerance test versus a 2-step protocol using the 1-hour glucose tolerance test followed by the 3-hour glucose tolerance test if the 1-hour test was positive. The 1-step protocol diagnosed 85 more women with gestational diabetes (16.5% vs 8.5%; RR, 1.94). Other outcomes, including large-for-gestational-age, perinatal outcomes, hypertensive disorders of pregnancy, and primary cesarean delivery did not differ between the screening groups.
- The 1-step protocol diagnosed more women with gestational diabetes but did not lead to differences in pregnancy and birth outcomes. The 1-step protocol is simpler to implement and bypasses additional screening in women with an initial positive test on the 2-step protocol. However, the 1-step protocol also increases the likelihood of a gestational diabetes diagnosis without an improvement in outcomes, which may place unnecessary stress on women during their pregnancy.
abstract
This abstract is available on the publisher's site.
Access this abstract nowBACKGROUND
Gestational diabetes mellitus is common and is associated with an increased risk of adverse maternal and perinatal outcomes. Although experts recommend universal screening for gestational diabetes, consensus is lacking about which of two recommended screening approaches should be used.
METHODS
We performed a pragmatic, randomized trial comparing one-step screening (i.e., a glucose-tolerance test in which the blood glucose level was obtained after the oral administration of a 75-g glucose load in the fasting state) with two-step screening (a glucose challenge test in which the blood glucose level was obtained after the oral administration of a 50-g glucose load in the nonfasting state, followed, if positive, by an oral glucose-tolerance test with a 100-g glucose load in the fasting state) in all pregnant women who received care in two health systems. Guidelines for the treatment of gestational diabetes were consistent with the two screening approaches. The primary outcomes were a diagnosis of gestational diabetes, large-for-gestational-age infants, a perinatal composite outcome (stillbirth, neonatal death, shoulder dystocia, bone fracture, or any arm or hand nerve palsy related to birth injury), gestational hypertension or preeclampsia, and primary cesarean section.
RESULTS
A total of 23,792 women underwent randomization; women with more than one pregnancy during the trial could have been assigned to more than one type of screening. A total of 66% of the women in the one-step group and 92% of those in the two-step group adhered to the assigned screening. Gestational diabetes was diagnosed in 16.5% of the women assigned to the one-step approach and in 8.5% of those assigned to the two-step approach (unadjusted relative risk, 1.94; 97.5% confidence interval [CI], 1.79 to 2.11). In intention-to-treat analyses, the respective incidences of the other primary outcomes were as follows: large-for-gestational-age infants, 8.9% and 9.2% (relative risk, 0.95; 97.5% CI, 0.87 to 1.05); perinatal composite outcome, 3.1% and 3.0% (relative risk, 1.04; 97.5% CI, 0.88 to 1.23); gestational hypertension or preeclampsia, 13.6% and 13.5% (relative risk, 1.00; 97.5% CI, 0.93 to 1.08); and primary cesarean section, 24.0% and 24.6% (relative risk, 0.98; 97.5% CI, 0.93 to 1.02). The results were materially unchanged in intention-to-treat analyses with inverse probability weighting to account for differential adherence to the screening approaches.
CONCLUSIONS
Despite more diagnoses of gestational diabetes with the one-step approach than with the two-step approach, there were no significant between-group differences in the risks of the primary outcomes relating to perinatal and maternal complications. (Funded by the Eunice Kennedy Shriver National Institute of Child Health and Human Development; ScreenR2GDM ClinicalTrials.gov number, NCT02266758.).
Additional Info
A Pragmatic, Randomized Clinical Trial of Gestational Diabetes Screening
N. Engl. J. Med 2021 Mar 11;384(10)895-904, TA Hillier, KL Pedula, KK Ogasawara, KK Vesco, CES Oshiro, SL Lubarsky, J Van MarterFrom MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
Primary Care
In a randomized trial of almost 24,000 pregnant women, researchers compared a one-step, 75-g glucose load with a two-step, 50-g (followed by 100-g if positive) glucose load for gestational diabetes screening. Researchers found higher rates of gestational diabetes diagnosis with the one-step screen. However, pertinent maternal and neonatal outcomes (including hypertensive disorders of pregnancy, primary cesarean section, large-for-gestational age infants, shoulder dystocia, stillbirth) were not different between the two groups.
Although the trial shows more disease identification with a one-step glucose load, the question is at what cost? More identification does not necessarily result in better disease outcomes. Infants are just as likely in either group to be large-for-gestational age, for example. So, if you’re identifying more cases of gestational diabetes without changing related disease outcomes, then is the screening or disease diagnosis harmful in any way? The one-step screening certainly streamlines the process for diagnosis by eliminating a follow-up appointment. There may also be some benefit to identifying more patients with gestational diabetes related to future risk for both mother and infant as gestational diabetes is associated with higher rates of type 2 diabetes diagnosis and childhood obesity. However, by identifying more disease, the burden of disease diagnosis is significant with multiple daily glucose checks for the remainder of pregnancy as well as the mental and emotional toll diagnosis can have on a pregnant woman.
Based on this trial, the evidence shows either approach, one-step or two-step, is appropriate. There doesn’t seem to be any compelling evidence at this time to know if one approach is better, but we know there isn’t more harm associated with either screening strategy (at least based on the outcomes assessed in the trial). As a family physician who continues to practice obstetrics, I’ve been at institutions that have used the two-step approach and I’ve been at institutions that used the one-step. My perspective is it seems clinically appropriate to use either and it may be worthwhile to individualize the screening tool to the patient, both having a discussion with the patient about benefits and harms as well as considering other factors such as difficulty with attending appointments or even the interruption of a global pandemic.