The Effect of Covid-19 Infection in Early Pregnancy on Hematological Parameters and Miscarriage Rate


 Purpose Based on the fact that Coronavirus Disease 2019 (Covid-19) is assosiated with many hemocytometric changes, in this clinical trial we aimed to investigate the effect of this underlying inflammatory process on the frequency of miscarriage.Methods This is a retrospective cohort study. Patients with laboratory-confirmed Covid-19 infection before the 20th gestational week were determined as the study group. Healthy pregnant women in their early pregnancy were determined as the control group. Hematological parameters of all patients included in the analysis were evaluated.ResultsA total of 176 pregnant women with confirmed Covid-19 infections were evaluated, of which 117 were included in the analysis. 117 healthy pregnant women were determined as the control group. There was no difference between the groups according to demographic characteristics. The median white blood cell (WBC) and lymphocyte levels were lower in patients with Covid-19 infection (p<0.001, p<0.001). The value of platelet/lymphocyte ratio (PLR) was higher in the group with Covid-19 infection (160.95 vs 132.42, p<0.001). It was also determined that the median plateletcrit level was lower in the group with Covid-19 infection (p<0.001). The miscarriage rate in the Covid -19 infection group and control group was 14.2% and 9.4%, respectively. (p=0.220).ConclusionCovid-19 infection presents with low lymphocyte count and plateletcrit values ​​in pregnant women, and an increase in PLR rates in relation to the severity of the disease is observed. Although not statistically significant, Covid-19 infection was associated with increased miscarriage rates in our study.


Introduction
Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) infection, which mainly presents with respiratory system symptoms, has the potential to turn into a multisystem disease and affects pregnant women as well as the entire population. Although it was stated that the effect of the infection on pregnant women at the beginning of the pandemy was similar to the general population, it has been observed that it may progress more severely in pregnant women in the following periods [1,2].
Studies have shown that there is an increase in the frequency of preterm birth and cesarean section in cases with Coronavirus disease 2019 (Covid-19) infection during pregnancy [3]. The effect of Covid-19 infection on the frequency of abortion is not yet clear. Studies in the literature evaluating the relationship between SARS-CoV-2 infection and abortion risk are mostly in the form of case reports.
Complete blood count is the rst laboratory test used in the evaluation of infectious diseases. During the Covid -19 pandemic, the relationship of many hematological parameters with the severity of the disease has been studied [4,5]. Neutrophil-lymphocyte ratio (NLR), platelet-lymphocyte ratio (PLR), mean platelet volume (MPV), which can be easily reached through routine hematological parameters, are indicators of in ammatory status that have also been studied in obstetric practice [6]. NLR which is studied in the rst trimester can give an idea about possible complications in pregnancy [7]. For example, increased NLR was found to be associated with severe preeclampsia, gestational diabetes, gestational cholestasis, hyperemesis gravidarum, early pregnancy loss and preterm labor [8,9].
There are also studies in the literature investigating the relationship between the platelet indices and the risk of miscarriage [10][11][12]. Studies have shown that low MPV, lymphopenia, and high PLR are associated with early pregnancy losses [9,11].
Although there are many studies in the literature on the course of Covid-19 infection in pregnant women, there is a need for good quality studies to illuminate its relationship with early pregnancy complications.
Based on the fact that Covid-19 infection is a process that occurs with changes in hematological parameters that support in ammation, we planned to investigate the effect of this underlying in ammatory process on the frequency of miscarriage.
To the best of our knowledge, this is the rst study to evaluate the risk of miscarriage in pregnant women with Covid-19 infection under 20 weeks of gestation, along with associated hematological parameters.

Materials And Methods
This is a retrospective cohort study. Pregnant women under 20 weeks of gestation who were evaluated for Covid-19 infection in Bursa City Hospital Gynecology and Obstetrics Department between December 2020 and June 2021 were included in the study. The study was approved by Bursa City Hospital Clinical Research Ethics Committee (Approvel number: 2021-11/1). Patients with laboratory con rmed Covid-19 infection before the 20th gestational week were determined as the study group. Laboratory diagnosis of infection was made by real time polymerase chain reaction (RT-PCR) test. Body mass index, obstetric history, and hematological parameters of the patients were examined. In the study, blood samples taken from all study participants at the time of admission were evaluated. Only patients whose hematological parameters could be reached were included in the study. Neutrophil/lymphocyte and platelet/lymphocyte ratios were calculated for all patients included in the analysis. Pregnant women who had a Covid-19 infection before the 20th gestational week were determined as study group (Covid +), pregnant women who did not have a history of Covid-19 infection at <20 weeks as control group (Covid -). Data from 117 patients in both groups were included in the analysis. The patients in both groups were followed up through the hospital database until the 20th gestational week and beyond. Both groups were comparable with respect to demographic parameters. In the subgroup analysis, comparisons were made as the control group, the inpatient group and the outpatient group. After RT-PCR positivity patients who had miscarriage at the time of admission to the hospital or during hospitalization were considered as miscarriage associated with Covid-19 infection.

Statistical analysis
The Shapiro-Wilk test was used to assess whether the variables followed a normal distribution.
Variables were reported as mean±standart deviation and median (minimum:maximum) values. According to the normality test results, Independent samples t-test, Mann-Whitney's U-test and Kruskal Wallis test were used to compare the groups. Comparison of abortion rates between covid infected and non-infected groups was made using the chi-square test. The relationships between age and hematological measurements were examined by correlation analysis and Spearman correlation coe cient was calculated. Statistical analyses were performed by using SPSS version 23.0 (SPSS Inc., Chicago, IL, USA). A p-value of 5% was considered statistically signi cant for all statistical comparisons.

Results
A total of 176 pregnant women who were con rmed to have Covid-19 infection by Polymerase Chain Reaction (PCR) test for SARS-CoV-2 on combined oropharyngeal and nasopharyngeal swabs were included in the study. 59 patients who did not have blood tests or whose blood tests could not be reached were excluded. 117 healthy pregnant women were determined as the control group ( Figure 1).
Demographic characteristics of the patients in the study and control groups are shown in Table 1. There was no difference between the groups according to demographic characteristics (Table 1).   In the subgroup analysis, it was determined that the median WBC levels of the outpatient and inpatient groups were lower than the patients who did not have Covid-19 infection (p<0.001 and p<0.001, respectively). Lymphocyte values also differed between groups (p<0.001). In the subgroup analysis, it was determined that the median lymphocyte levels of the outpatient and inpatient groups were lower than the patients who did not have Covid-19 infection (p<0.001 and p<0.001, respectively). It was determined that the median PLR values of the outpatient and inpatient groups were higher than the patients who did not have Covid-19 infection (p=0.008 and p<0.001, respectively). Again, in the subgroup analysis, it was determined that the median PCT levels of the outpatient and inpatient groups were lower than the patients who did not have Covid-19 infection (p=0.001 and p<0.001, respectively). On the other hand there was no difference in terms of NLR ratio, MPV and PDW levels between the groups (p>0.05) ( Table 4). It was determined that there was no relationship between age and hematological measurements in patient groups with and without Covid-19 infection.
While miscarriage was observed in 14.20% (n=25) of 176 patients who had Covid-19 infection, this rate was determined as 9.40% (n=11) in 117 patients who did not have Covid-19 infection, and no statistically signi cant difference was observed between the groups in terms of miscarriage rates (p=0.220).

Discussion
With the identi cation of the rst cases in December 2019, the Covid-19 pandemic has affected the whole world as the rst case in Turkey was described on March 11, 2020 [13]. The effect of this infection on pregnant women contains many uncertainties [14]. There are case reports in the literature reporting pregnancy loss before the 20th week during Covid-19 infection [3,[15][16][17]. However, studies on a large patient population in early gestational weeks are not available. The studies conducted mostly cover the 3rd trimester pregnant women. Unlike other studies in the literature, our study only included patients at early gestational weeks.
Hassanipour et al. reported a signi cant increase in neutrophils in patients and mortality accompanied by decreased lymphocyte count in one case [18]. It has been reported in many studies that increased NLR during SARS -Cov -2 infection is associated with poor prognosis [19][20][21][22]. In our study, although there was a slight increase in the inpatient group compared to the control group, no signi cant increase was observed in NLR rates. This increase was more pronounced in the group of patients with Covid -19 infection whose pregnancy ended with miscarriage even if the difference did not reach a statistically signi cant level.
Erol Koç et al. evaluated hematological parameters and pregnancy outcomes in pregnant women with Covid-19 infection. While there was no difference between obstetric and neonatal outcomes, NLR was found to be high, and plateletcrit was found to be low in Covid-19 infection group [23].
It has been shown that the lymphocyte count and NLR ratio at the time of admission are related to the severity of the disease [24,25]. While no difference was observed in NLR rates in our study group, it was observed that lymphopenia became more pronounced with disease severity. All authors contributed to the nal revision of the manuscript.

Disclosure of interests
No con ict of interest for any of the authors.

Funding
No funding or other nancial support was received for this study.

Statement of Ethics
This study was approved by the Bursa City Hospital Clinical Research Ethics Committee (Approval number: 2021-11/1).

Figure 1
Flowchart of patient selection