Oxidative stress status and vitamin D levels of asymptomatic to mild symptomatic COVID-19 infections during the third trimester of pregnancy: A retrospective study in Metz, France

Abstract

It is believed that the subtle equilibrium between tolerance and immunity during the unique biological state of pregnancy, which is characterized by further physiological and hormonal changes, rends pregnant women more vulnerable to coronavirus disease 2019 (COVID-19). In this retrospective study, confirmed COVID-19-positive pregnant women (n = 15) during their third trimester, comprising asymptomatic (n = 7) and mild symptomatic (n = 8), and healthy pregnant controls (n = 20), were enrolled between June 1, 2020 and June 1, 2021 from the Hospital CHR Metz-Thionville in Metz, France. Vitamin D concentrations, C-reactive protein (CRP), and oxidative stress markers including superoxide dismutase (SOD), catalase (CAT), reduced (GSH) and oxidized (GSSG) glutathione levels, hydrogen peroxide (H₂ O₂ ), and the total antioxidant capacity, measured the ferric reducing ability of plasma (FRAP), were evaluated in the serum of patients and controls. Results showed that all pregnant women (patients and controls) enrolled in this study were vitamin D deficient (<20 ng/ml). However, mild COVID-19 pregnant women were severely vitamin D deficient (<12 ng/ml), which may suggest a link between vitamin D deficiency and the symptomatology of COVID-19 illness in singleton pregnancy. No differences between the levels of CRP and the majority of the studied oxidative stress markers in COVID-19-positive pregnant women (asymptomatic and/or mildly symptomatic patients) versus COVID-19-negative pregnant women were found, suggesting the absence or a low magnitude of oxidative stress in pregnant women with COVID-19. This may also explain the absence of severe courses of COVID-19 infection. More studies are warranted to investigate the role of vitamin D supplementation and antioxidant-rich diets in the prevention against severe forms of COVID-19 in pregnant women.

Keywords: C-reactive protein (CRP); COVID-19; SARS-CoV-2; oxidative stress; pregnancy; vitamin D.

Figure 1

Serum vitamin D (25(OH)D) concentrations (ng/ml) in COVID‐19 pregnant women (n = 15) and non‐COVID pregnant women (n = 19) during the third trimester. *p ≤ 0.05 significantly different from the controls. ^# p ≤ 0.05 significantly different from asymptomatic COVID‐19 pregnant women. All COVID‐19 patients were constituted by asymptomatic (n = 7) and mild symptomatic (n = 8) patients. Data are shown as box plots, indicating the median and the 25th and 75th percentiles

Figure 2

C‐reactive protein (CRP) levels (mg/L) in COVID‐19 pregnant women (n = 14) and non‐COVID pregnant women (n = 12). All COVID‐19 patients were constituted by asymptomatic (n = 6) and mild symptomatic (n = 8) patients. Data are shown as box plots, indicating the median and the 25th and 75th percentiles

Figure 3

Oxidative stress markers in COVID‐19 pregnant women (n = 15) and non‐COVID pregnant women (n = 19−20) during the third trimester. (A) Superoxide dismutase (SOD) activity expressed in (U/ml). (B) Catalase (CAT) activity expressed in (U/ml). (C) Reduced glutathione levels (GSH) expressed in μM. (D) Oxidized glutathione levels (GSSG) expressed in μM. (E) Hydrogen peroxide (H₂O₂) concentrations expressed in μM. (F) FRAP values reflecting the total antioxidant capacity (μM) were expressed in μM. *p < 0.05 significantly different from the controls. ^# p < 0.05 significantly different from asymptomatic COVID‐19 pregnant women. All COVID‐19 patients were constituted by asymptomatic (n = 7) and mild symptomatic (n = 8) patients. Data are shown as box plots, indicating the median and the 25th and 75th percentiles. FRAP, ferric reducing ability of plasma