Findings suggest it may be safe to wait for gestational diabetes testing until later in pregnancy with no increased risk to baby
People with risk factors for gestational diabetes can safely skip an early pregnancy glucose screening test given before 24 weeks gestation, according to a large new study by Kaiser Permanente researchers.
Alternatively, these higher-risk patients can follow a path that emphasizes early pregnancy screening for type 2 (chronic) diabetes, nutritional counseling, and gestational diabetes screening at the typical timing of 24 to 28 weeks gestation, the researchers said.
The study of more than 220,000 deliveries at Kaiser Permanente Northern California (KPNC) was published in Obstetrics & Gynecology.
“The purpose of screening for gestational diabetes is to regulate fetal growth and development, and much of the interaction between blood sugar and the fetus takes place later in pregnancy,“ said lead author Mara Greenberg, MD, a maternal/fetal medicine specialist with The Permanente Medical Group and adjunct investigator with the Kaiser Permanente Division of Research (DOR).
Clinicians must weigh the pros and cons of diagnosing gestational diabetes early in pregnancy. They consider not only the potential health impact of blood sugar irregularity in early pregnancy, but also the potential effects of intensive monitoring, lifestyle changes, and treatment with medication if the diagnosis is made earlier rather than later in pregnancy.
“We used to screen early in pregnancy on the assumption earlier detection is always better, but we also have to weigh whether the very intensive steps it takes to manage glucose intolerance for many more weeks are worthwhile for our pregnant patients and newborns,” Greenberg said.
Once diagnosed with gestational diabetes, the typical care journey for a pregnant patient includes nutritional counseling, major changes to their diet, checking blood sugar 4 times per day and reporting results to the health care team, starting a program of physical activity, and in many cases taking medication such as insulin.
The study provides evidence, from a large group of patients, that supports a recommendation from the American College of Obstetricians and Gynecologists to skip early testing before 24 weeks.
At the same time, doctors want to be sure to catch cases of type 2, or chronic, diabetes in early pregnancy, as it can cause serious complications during a pregnancy.
Gestational diabetes mellitus is a form of high blood sugar related to changes in metabolism during pregnancy; it is identified through an oral glucose challenge test. Type 2 diabetes is a separate metabolic condition and it can be diagnosed with a blood test known as the HbA1C that measures average blood sugar levels over time. The two conditions are identified and managed differently. Women who develop gestational diabetes are at higher risk of later developing type 2 diabetes.
Natural experiment using pandemic-era data
The researchers took advantage of the clinical changes implemented in April 2020 in response to the shelter-in-place for the COVID-19 pandemic. They designed their study to track health outcomes before, during, and after a KPNC decision in April 2020 to begin moving away from gestational diabetes screening before the standard screening time of 24-28 weeks’ gestation, while emphasizing screening for Type 2 diabetes.
The change was made as published evidence began to accumulate that early diagnosis did not benefit the infant. Also, pandemic changes in care delivery meant it was harder for patients to come to a laboratory for testing in person, and KPNC clinical leaders wanted to ensure timing of screening would benefit patients.
The study split the pregnancies into 3 time periods so the patients’ care and outcomes could be compared as practice gradually changed. The first group covered deliveries in the 2 years prior to 2020; the second group measured much of 2020; and third period was 2021 to 2022.
The study found early pregnancy gestational diabetes screening rates dropped over time, from 31% in the first period, to 21% in 2020, to 4.3% in the last period.
The researchers did not find any difference in health outcomes for pregnant individuals and babies in the study. They looked for differences in several outcomes: large-for-gestational age baby, caesarean section, preeclampsia, severe maternal morbidity, preterm birth, shoulder dystocia, neonatal hypoglycemia, and NICU admission.
The statistical analysis method comparing 3 time periods is a strength of the study, said senior author Assiamira Ferrara, MD, PhD, a DOR research scientist who leads its UPSTREAM Center, which is focused on prevention of obesity and diabetes. “We used a quasi-experimental interrupted time series design that is used to evaluate the effect of population-level health interventions, with the aim of estimating causal effects using observational data when randomization is not possible,” she said.
KPNC tests nearly all pregnant patients for gestational diabetes at some point in the pregnancy, usually around 24-26 weeks gestation. While practice recommendations were changed in April 2020, ob/gyn physicians were also free to use their own judgment on screening and treatment with individual patients.
Increased chronic diabetes screening
At the same time, KPNC also decided to increase its focus on testing for type 2 diabetes at the first prenatal visit among people with risk factors. While most patients with type 2 diabetes are identified before pregnancy, Greenberg said, not all of them are, so a prenatal visit is an opportunity to screen for a significant health disorder.
The study found the new emphasis resulted in a steady rise in the percentage of patients getting an A1C test in early pregnancy to identify type 2 diabetes, though the actual number of patients identified was very small. A new diagnosis of type 2 diabetes in early pregnancy, while rare, can have serious implications for the health of pregnant individuals and their babies and requires more intensive treatment and follow up than gestational diabetes.
“We believe these findings support a move away from early gestational diabetes screening, accompanied by an increase in chronic diabetes screening in early pregnancy,” Greenberg said. “This study is an important addition to the existing evidence base because of its large size, diverse patient population, and sophisticated comparisons over time.”
“At the same time,” she added, “this nuanced area of patient care affects the well-being of many pregnant patients and babies, with many questions about optimal screening, testing, and management strategies still unanswered. We hope to continue contributing to identification of the best clinical approaches through ongoing implementation science research.”
The study was funded by The Permanente Medical Group.
Additional co-authors were Yeyi Zhu, PhD, Monique M. Hedderson, PhD, Charles P. Quesenberry, PhD, Jun Shan, PhD, and Amanda Ngo, MS, all of the Division of Research.
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About the Kaiser Permanente Division of Research
The Kaiser Permanente Division of Research conducts, publishes, and disseminates epidemiologic and health services research to improve the health and medical care of Kaiser Permanente members and society at large. KPDOR seeks to understand the determinants of illness and well-being and to improve the quality and cost-effectiveness of health care. Currently, DOR’s 720-plus staff, including 73 research and staff scientists, are working on nearly 630 epidemiological and health services research projects. For more information, visit divisionofresearch.kp.org or follow us @KPDOR.
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