Objective: to investigate a possible bi-directional association between gestational diabetes (GDM) and the SARS-CoV-2 infection during pregnancy. Design: case-control study with prospective data collection for the case group and 1:2 matching with historical controls Setting: University Hospital of Bern, Switzerland Population: 224 pregnant women: 75 cases with SARS-CoV-2 infection during pregnancy, matched 1:2 with controls based on parity, BMI and ethnicity. Methods: SARS-CoV-2 infection was diagnosed by RT-PCR. Screening for GDM was performed by 75mg oral glucose tolerance test at 26 weeks’ gestation in all women. Main Outcomes: Prevalence of GDM was calculated in both groups. Multivariate binary logistic regression analysis was performed to assess risk factors for GDM and inpatient COVID-19 management. Results: 34.6% of the patients in the case group suffered from GDM, vs. 16.1% in the control group (p=0.002). 35.7% patients were diagnosed with GDM after the SARS-CoV-2 infection, vs. 33.3% diagnosed before infection (OR(95%CI) 1.11(0.40-3.08), p=0.84), with no correlation between the time-point of infection and GDM diagnosis. SARS-CoV-2 (OR(95%CI) 2.79 (1.42, 5.47), p=0.003) and BMI (OR(95%CI) 1.12 (1.05, 1.19), p=0.001) were significant independent risk factors for GDM. Conclusions: The significantly higher rate of GDM among women with SARS-CoV-2 infection during pregnancy, as compared to matching controls, suggests that GDM increases the risk of infection. On the other hand, SARS-CoV-2 during pregnancy might increase the risk of developing GDM. Vaccination and caution in using protective measures should be recommended to pregnant women, particularly those with co-morbidities. Funding: none Keywords: SARS-CoV-2, gestational diabetes, COVID-19