There are studies on COVID-19 cases seen during pregnancy, and in some studies, it has been reported that COVID-19 infection is associated with adverse pregnancy outcomes [1, 2]; however, this relationship is still remains controversial . In the present study, we found that the COVID-19-positive pregnant group and healthy pregnant women were similar in terms of the mean week of delivery and the mean birth weight. In addition, no significant correlations were observed between the clinical picture levels, the gestational age at the time of COVID-19 infection, and the week of delivery and birth weight. These findings indicate that COVID-19 infection per se does not have a direct effect on preterm labor or low birth weight. However, it is not clear from these findings whether there is an effect of COVID-19 on preterm labor or low birth weight due to the absence of low birth weight cases in the study and a relatively lower number of preterm births.
IFN-γ is an immune system molecule that is released from helper T cells as a result of stimulation of various antigens, and has a significant effect on macrophages with more pronounced immunomodulatory effect than other interferons, but a weaker antiviral effect. IFN-γ levels increase have been reported in many disease conditions such as infectious, autoimmune disorders, and cancers [6, 22–24]. It was reported that IFN-γ is also released from trophoblasts, specialized natural killer cells, and decidual cells during pregnancy . It has been reported that IFN-γ also involves in such events as differentiation of decidual natural killer cells and formation of placenta during pregnancy, which played roles in defense against viruses and tumoral formations [7, 26]. Furthermore, it was reported that IFN-γ is associated with pregnancy loss, especially in conditions such as congenital infection . Studies showed that excessive secretion of IFN-γ during pregnancy is associated with pre-eclampsia [8, 28]. In a recent study, IFN-γ levels were reported to be significantly higher in pregnant women with COVID-19 infection compared to healthy pregnant women, suggesting that COVID-19 had an effect on IFN-γ and some cytokine levels in pregnant women . IFN-γ has also been shown to be a risk factor for mortality in moderate and severe COVID-19 cases . In our present study, the mean IFN-γ levels in specimens obtained from mother, newborn and placenta of pregnant women with COVID-19 infection were significantly lower than those in the control group. This finding shows that IFN-γ levels are significantly decreased in pregnant women who have had COVID-19 infection. In the ROC analysis, the cutoff value of 225.63 pg/mg protein for the IFN-γ level in the maternal sample was found to have a sensitivity of 81.8% and a specificity of 85.7% for the determination of post-COVID-19 infection. Our findings thus imply that IFN-γ level is a highly reliable biomarker that can be used in the diagnosis of COVID-19 in pregnant women. Furthermore, a significantly inverse correlation was found between the gestational age at the time of COVID-19 infection and IFN-γ levels, means that IFN-γ levels decreases even more markedly if the pregnant woman had COVID-19 close to the delivery stage.
IRF5 is a transcription factor that regulates the immune response, it also regulates the activities of genes belonging to type 1 interferons and related cytokines. Studies have shown that IRF5 plays important role in anti-viral and inflammatory response processes, and the polymorphism that occurs in IRF5 can lead to some autoimmune diseases [11, 12]. It has also been reported that the suppressed IRF5 production under normoxic conditions modulated (suppressed) the production of other pro-inflammatory cytokines . Furthermow, it has been shown that IRF5 plays a role in the regulation of inflammatory response in myometrium and that the IRF5 expression level increases in the myometrium with labor . Study has shown that gene polymorphisms occurring in IRF5 were associated with recurrent spontaneous abortions . It was reported that IRF5 played a role in cytokine storm seen in some infections such as COVID-19, and that suppression of IRF5 might be beneficial in order to maintain the clinical status in these cases . In the present study, we observed that the mean IRF5 levels in specimens obtained from the maternal, newborn and placenta of COVID-19 group were significantly lower than the controls. This finding clearly demonstrates that the level of IRF5 decreases significantly in pregnant women who have had COVID-19. In the ROC analysis, we found that the cutoff value of 2,015 ng/mg protein for maternal IRF5 had a sensitivity of 81.8% and a specificity of 82.5% for the determination of post-COVID-19 infection. Again, this finding highlights that IRF5 level is also a reliable biomarker that can be used in the diagnosis of COVID-19 in pregnant women. Interestingly, a significantly inverse correlation was found between the gestational age at during COVID-19 infection and IRF5 levels. This finding suggests that the IRF5 level is significantly lower in COVID-19 cases close to the delivery stage. Considering that the level of IRF5 is lower in COVID-19 cases than in those who do not have COVID-19, this finding means that the decrease becomes more pronounced in cases where the pregnant woman had COVID-19 infection close to the delivery stage.
HIF-1 is a transcription factor induced in hypoxic conditions and is an important regulator of gene expression . HIF-1 works to supply tissues with oxygen and help cells recover from a lack of oxygen. In this context, it leads to erythropoiesis by increasing erythropoietin production in response to hypoxia, and angiogenesis by inducing vascular endothelial growth factor . It has been reported that HIF-1α is elevated in infected cells in some viral infections . It has also been stated that hypoxia plays role in the pathogenesis and progression of COVID-19, showing that the level of HIF-1α increased in COVID-19 cases, especially in critically ill patients [11, 30]. In addition, endothelial damage has been reported in COVID-19 cases, which was proven by the high levels of HIF-1α . A study has suggested that hypoxia and the resulting HIF-1α might be related to the cytokine storm seen in the clinical picture of COVID-19 . It has also been suggested that stabilization of HIF-1α in COVID-19 cases might be beneficial in combating the disease . In addition, it was reported that hypoxia and HIF-1α played a role in the pathogenesis of pre-eclampsia in pregnant women . In a study, it was shown that high level of HIF-1α in pregnant women was associated with pre-term delivery . In our present study, the mean HIF-1α levels in specimens obtained from maternal, newborn and placenta of pregnant women with COVID-19 infection were found to be significantly higher, suggesting that HIF-1α levels are significantly increased in pregnant women who have had COVID-19 infection.
It is interesting to note that in the present study, a positive correlation was found between the gestational age at the time of COVID-19 and the HIF-1α level in the samples taken from the newborn, and a positive correlation with the HIF-1α level in the samples taken from the placenta, but no significant correlation was found with the HIF-1α level in the maternal samples. These findings demostrate that the effect of COVID-19 on HIF-1α level may be variable. Further translational studies will be desiarable b to better clarify this observation. However, in the ROC analysis, the cut-off value of 266.08 ng/mL for the HIF-1α level in the sample taken from the mother was found to have 72.7% sensitivity and 83.3% specificity in the diagnosis of COVID-19. This finding suggest that the level of HIF-1α is also a reliable biomarker that can be used in the diagnosis of COVID-19 in pregnant women.
In the ROC analyees, the cutoff values determined for IRF5, IFN-γ and HIF-1α levels in blood samples taken from the newborn after birth were found to be over 80% in terms of sensitivity and specificity in determining the mother's COVID-19 history during pregnancy. This finding shows that IRF5, IFN-γ, and HIF-1α levels in infant blood samples can be used as reliable biomarkers for maternal COVID-19. In a study, it was shown that the risk of pre-term birth increased in pregnant women with high IFN-γ levels . In the present study, week of delivery and birth weight did not significantly correlated with IRF5, IFN-γ, and HIF-1α levels. When evaluated together with the findings that IRF5, IFN-γ, and HIF-1α levels change significantly in COVID-19-positive cases and the mean week of delivery and birth weight do not change in these cases, these findings support the idea that COVID-19 may not have a direct effect on preterm labor or low birth weight. In a meta-analysis, it was reported that IFN-γ levels were significantly higher in severe COVID-19-positive cases compared to the relatively mild or moderate cases . In our present study, the mean IRF5, IFN-γ, and HIF-1α levels were found to be similar between the patients with asymptomatic/mild clinical picture and patients with severe COVID-19. This finding shows that the severity of COVID-19 clinical picture in pregnant women may not have a direct and significant effect on IRF5, IFN-γ, and HIF-1α levels.
As with any study, there are some potential limitations with our study, i.e., it could not be evaluated whether COVID-19 positivity had an effect on low weight or pre-term labor, since there were no pregnant women who had a low birth weight in the patient cohort and the number of pregnant women who had premature birth was relatively very low. Also, it was thought that there might be a margin of statistical error in the analyses related to the clinical picture, since there was no pregnancy case with a moderate and critical clinical picture in those who had COVID-19 infection. Nonetheless, the present study is the first attempt in which IRF5, IFN-γ, and HIF-1α levels in pregnant women with COVID-19 positivity have been evaluated in samples taken from both maternal, infant and placental blood. Our findings suggest that COVID-19 infection has a significant effect on IRF5, IFN-γ, and HIF-1α levels / exprssion in pregnant women. This study also implies that IRF5, IFN-γ, and HIF-1α levels can be used as a highly bioreliable marker while diagnosing of COVID-19 in pregnant women.