- Abstract Objective: To examine possible correlation between α1-antitrypsin (AAT) levels and activity in patients with and without obesity, after excluding complications such as gestational diabetes mellitus (GDM), during pregnancy. Study design: A prospective case-control study was conducted. AAT levels were determined by standard human AAT ELISA according to the manufacturer's instructions. Elastase inhibition was determined by kinetic assay according to manufacturer recommendations. Assays were performed in duplicates and repeated twice for each sample in separate sessions. Patients with diabetes mellitus were excluded from the study. Mann-Whitney U-test was performed in order to determine statistical differences between the groups, and AAT concentration and activity. Results: During the study period 43 patients were recruited: 21 with isolated obesity and 22 non-obese parturients (control group). According to ELISA, AAT concentrations were mildly lower in obese women compared to non-obese women (8.31 ± 0.28 mg/ml vs. 9.5 ± 0.37 mg/ml, p=0.0155). However, elastase inhibitory capacity was markedly lower in obese vs. non-obese parturients (mean 27.33 ± 2.08 % vs. 43.73 ± 3.1%, p<0.001). Conclusions: Isolated obesity in pregnancy is associated with lower activity of AAT. These findings correlate with the reduced concentration and activity of AAT found in patients with GDM. Accordingly, it might suggest an inflammatory axis shared by obesity and the development of insulin resistance.