Impact of earlier gestational diabetes screening for pregnant people with obesity on maternal and perinatal outcomes

Abstract

Objectives: Gestational diabetes (GDM) screening at 24-28 weeks' gestation reduces risk of adverse maternal and perinatal outcomes. While experts recommend first-trimester screening for high-risk patients, including those with obesity, data supporting this recommendation is limited.

Methods: We implemented a systematic population intervention to encourage first-trimester GDM screening by oral glucose tolerance testing in a cohort of pregnant people with obesity in two integrated health systems from 2009 to 2013, and compared outcomes to the same population pre-intervention (2006-2009). Up to five years of postpartum glucose testing results (through 2018) were assessed among GDM cases in the post-intervention group. Primary outcomes were large-for-gestational-age birthweight (LGA); macrosomia; a perinatal composite outcome; gestational hypertension/preeclampsia; cesarean delivery; and medication treatment of GDM.

Results: A total of 40,206 patients (9,156 with obesity) were screened for GDM; 2,672 (6.6%) were diagnosed with GDM. Overall, multivariate adjusted risk for LGA and cesarean delivery were lower following the intervention (LGA: aOR 0.89 [0.82, 0.96]; cesarean delivery: 0.89 [0.85, 0.93]). This difference was more pronounced in patients diagnosed with GDM (LGA: aOR 0.52 [0.39, 0.70]; cesarean delivery 0.78 [0.65, 0.94]); insulin/oral hypoglycemic treatment rates for GDM were also higher post-intervention than pre-intervention (22 vs. 29%; p<0.0001). There were no differences for the other primary outcomes. Only 20% of patients diagnosed with GDM early in pregnancy who had postpartum testing had results in the overt diabetes range, suggesting a spectrum of diabetes detected early in pregnancy.

Conclusions: First trimester GDM screening for pregnant people with obesity may improve GDM-associated outcomes.

Keywords: early gestational diabetes; early gestational diabetes screening; early pregnancy; gestational diabetes (GDM); intervention; obesity; timing of screening.

Figure 1:

Histogram of gestational age (in weeks) of first glucose screening test in the population before (pre) and after (post) the early gestational diabetes mellitus (GDM) screening intervention (n=40,206). Post-intervention exhibits a shift to a bimodal distribution in the population with a markedly higher mode at 10 weeks’ gestation, representing the increased frequency of early screening in the first trimester.

Figure 2:

Adjusted odds ratios comparing outcomes post-intervention vs. pre-intervention for 1) all pregnancies in the full population (n=40,206) and among all patients with gestational diabetes mellitus (GDM; n=2,672) and 2) all patients with obesity (n=9,156) and patients with obesity and GDM (n=976). Intervention was earlier GDM screening targeting patients with obesity. Odds ratios (ORs) for maternal and perinatal outcomes are adjusted for maternal age, race/ethnicity, nulliparity, prior hypertension, pre-pregnancy obesity (for models on the full population), site and, with the exception of models evaluating insulin or oral medication use, exceeding National Academy of Medicine (NAM) weight gain guidelines. For the full population groups, ORs are also adjusted for hierarchical elevated glucose, and all cesarean delivery models were also adjusted for birthweight >4,000 g. Among all patients with obesity, the interaction term of intervention period x exceeding NAM weight gain guidelines is significant for gestational hypertension/preeclampsia. Stratification by exceeding NAM weight gain guidelines yields the following OR (95% CI) for post- vs. pre- intervention: weight gain exceeds guidelines OR=0.73 (0.61, 0.88); Weight gain does not exceed guidelines OR=0.88 (0.69, 1.12); missing weight gain OR=0.65 (0.47, 0.91).

Figure 3:

Postpartum glucose screening within 5 years of delivery among patients diagnosed with gestational diabetes mellitus (GDM) in the post-intervention period, by timing of diagnosis. The targeted gestational age of early screening is the first trimester (<12 weeks) for high-risk patients and 24–28 weeks’ gestation for usual screening, and the 2nd diagnostic step of the oral glucose tolerance test (OGTT) is typically done about one week after initial screening. For analyses, we defined early GDM diagnosis as <18 weeks’ gestation and usual as ≥18 weeks’ gestation and the actual GDM diagnosis occurred at a median gestational 11 weeks’ gestation for early GDM and 29 weeks’ gestation for Usual GDM. Overall, 80.4% of patients diagnosed with GDM early in pregnancy (n=234) and 77.1% of those diagnosed with GDM later in pregnancy (n=910) had at least one diabetes screening test (Fasting plasma glucose (FPG), hemoglobin A1c (HbA_1c) or 75 g OGTT) in the 5 years following delivery. Results are stratified into the following three distinct categories based on postpartum testing: 1) any test meeting diabetes range criteria (positive test), 2) any test meeting impaired glucose range criteria and no test meeting diabetes range criteria, and 3) all tests were normal [4].