Association of Gestational Diabetes Mellitus With Maternal Outcomes and Risk Factors

Abstract

Background: Gestational diabetes mellitus (GDM) is among the most common complications seen during pregnancy in the US as well as worldwide. The prevalence of both GDM and severe maternal morbidity (SMM) are on the rise in the US. GDM results in short-term complications and long-term consequences in both mother and offspring. The studies on the association between GDM and SMM are limited. The evidence on the association between maternal smoking and hypothyroidism and GDM is conflicting. Objectives: The research objectives were: 1) to evaluate the associations between GDM and specific SMM indicators, including acute respiratory distress syndrome (ARDS), disseminated intravascular coagulation (DIC), sepsis, shock, and non-transfusion SMM, and 2) to describe the risk of GDM among females with a history of smoking and hypothyroidism. Methods: This thesis study was a retrospective, multi-year, nationwide, cross-sectional study using Healthcare Cost and Utilization Project (HCUP)-National Inpatient Sample (NIS) data (2012 to 2020). The study population consisted of delivery hospitalizations among females aged 15-49, identified using ICD-9-CM and ICD-10-CM codes. Continuous variables were compared using t-tests or Wilcoxon rank-sum tests after testing for normality. Categorical variables were compared using Pearson's Chi-square test. We used multivariable logistic regression models to estimate the odds ratios (ORs) and 95% confidence intervals (CIs). These models were developed with hypothyroidism and smoking as the primary exposures and GDM as the outcome, while adjusting for relevant factors and covariates selected based on clinical significance and a review of the literature. Multivariable log-binomial models were used to estimate the relative risks (RRs) of specific SMM outcomes and their 95% CIs with GDM as the primary exposure and age, hypothyroidism, and smoking status covariates for the adjusted models. Results: There were 34,121,910 delivery hospitalizations, out of which 3.5% had hypothyroidism and 8.64% were smokers. The proportion of GDM in delivery hospitalizations increased over the study period and was higher compared to those without hypothyroidism. Delivery hospitalization patients with hypothyroidism, compared to those without hypothyroidism, had a higher risk of GDM (adjusted OR (aOR), 1.31; 95% CI, 1.29-1.33; p<0.001). Smoking was poorly associated with GDM (aOR, 0.99; 95% CI, 0.98-1.00; p<0.001). Of the 34,121,910 delivery admissions, 2,546,450 were delivery hospitalization patients with GDM. The prevalence of GDM increased in the study population. However, the prevalence of non-transfusion SMM and DIC decreased in patients with GDM over the study period. Patients with GDM had a slightly higher risk of any SMM (adjusted RR (aRR), 1.05; 95% CI, 1.02–1.08; p < 0.001) and ARDS (aRR, 1.09; 95% CI, 1.00–1.18; p = 0.04) compared to patients without GDM. The risk of shock (aRR, 0.87; 95% CI, 0.78-0.97; p = 0.01) and sepsis (aRR, 0.92; 95% CI, 0.84–1.00; p = 0.05) were observed to be lower. GDM showed poor association with DIC (aRR, 0.98; 95% CI, 0.93-1.04; p = 0.6). Conclusions: This large nationwide study showed a higher risk of GDM in delivery hospitalization patients with hypothyroidism compared with those without hypothyroidism. There was a poor association observed between the history of smoking or current smoker status and GDM among patients hospitalized for delivery. Early screening for GDM may be offered to pregnant women with hypothyroidism. ARDS, DIC, and any non-transfusion SMM proportions were higher in delivery hospitalization patients with GDM than those without GDM. GDM was modestly associated with any SMM and ARDS. There was a poor association between GDM and DIC, and a lower risk of shock among women with GDM. The association remained mild for sepsis in the GDM group. Early diagnosis and optimal management of GDM would help to prevent ARDS, DIC, sepsis, shock, and any SMM and effectively manage SMM, if any. The results of this thesis research are important from a clinical and a public health perspective. Further, focused studies are needed to strategize how to prevent and manage SMM complications among women with GDM and to understand the association between hypothyroidism and smoking during pregnancy with GDM.