Study characteristics
306 articles were initially retrieved on the basis of the search strategies in the online databases. Among these articles, 97 duplicate publications were identified and removed. The remained ones were screened according to the titles and abstracts. 11 articles were selected as the final papers to be analyzed (Figure 1). The characteristics of 11 selected studies were demonstrated in Table 1. A total number of 177 pregnant women with COVID-19 were evaluated all in 2020 through 8 retrospectives, 1 case control, and 2 case report studies. The factors assessed in these studies involve gestational age, cesarean, vaginal delivery, chronic illness, indicators of cesarean, complications of pregnancy, signs and symptoms (fever on admission, cough, malaise, dyspnea, myalgia, sore throat, diarrhea, nausea and vomiting, fetal movement, fetal heart rate, vaginal bleeding, premature rupture of membrane, antepartum, post-partum), laboratory tests, imaging, treatment and other parameters (abnormal laboratory test, imaging, Bio Physical Profile, maternal mortality, maternal ICU admission, neonatal mortality, intrauterine fetal death, vertical transmission, treatments), and infant characteristics (birth weight, low birth weight, premature birth, Apgar score, intrauterine fetal distress, severe neonatal asphyxia, neonatal death, fetal death or stillbirth) (Table 1). Some studies had not reported the method of treatment. The studies which have reported the therapies applied for the patients have used both antibiotics and antivirals such as Oseltamiovir, Ganciclovir, Azithromycin and Ceftazidime. Two studies have used corticosteroids and two studies have used Chinese traditional medications which both of them had not explained about any benefits for the patients.
Quantitative analysis
Pooled prevalence of signs and symptoms in pregnant women with COVID 19
The least reported prevalence of fever in pregnant women with COVID 19 was 17% (95% Cl: 2 - 33%) in the study by Wang X. et al. and the highest fever as prevalence was recorded 86% (95% Cl: 60- 98%) in the retrospective study by Yu. et al. In total, the pooled prevalence of fever has been estimated as 56% (95% Cl: 30 - 83%; I2= 92.02%; P -Value < 0.01) (Figure 2 and Table 2). The Meta Regression was used to explore relationship of independent variables (age and gestational age) with the pooled prevalence of primary outcomes. The results of Meta regression showed that the prevalence of fever has not any relationship with age (coefficient: 0.029, P: 0.293, 95% CI: -0.026, 0.032), and gestational age of pregnant women with COVID 19 (coefficient: 0.023, P: 0.451, 95% CI: -0.021, 0.026).
The pooled prevalence of cough has been estimated as 30% (95% Cl: 21 - 39%; I2= 0.0%; P -Value = 0.37) (Figure 3 and Table 2). The least reported prevalence of cough in pregnant women with COVID 19 was 14% (95% Cl: 12 - 40%) in the study by Yu. et al. and the highest prevalence was recorded 55% (95% Cl: 25- 84%) in the retrospective study by Liu. et al (Figure 3). The results of Meta regression showed that the prevalence of cough has relationship with age (coefficient: 0.08, P: 0.001, 95% CI: 0.005, 0.010), and gestational age of pregnant women with COVID 19 (coefficient: 0.007, P: 0.001, 95% CI: 0.006, 0.011).
Also the pooled prevalence of dyspnea has been estimated as 3% (95% Cl: 1 - 6%; I2= 0.0%; P -Value = 0.76) (Figure 3 and Table 2). The least and highest reported prevalence of dyspnea in pregnant women with COVID 19 was 2% (95% Cl: 2 - 5%) and 50% (95% Cl: 19 - 95%), respectively (Figure 4 and Table 2). The results of Meta regression showed that the prevalence of dyspnea has relationship with age (coefficient: -0.0178, P: 0.046, 95% CI: -0.035, -0.000), and gestational age of pregnant women with COVID 19 (coefficient: -0.099, P: 0.326, 95% CI: -0.298, 0.099).
The pooled prevalence of myalgia, sore throat, and diarrhea in pregnant women with COVID 19 were 18% (95% Cl: 1 - 35%, I2= 49.84%; P -Value = 0.14), 7% (95% Cl: 1 - 13%, I2= 0.0%; P -Value = 0.55), and 9% (95% Cl: 2 - 16%, I2= 0.0%; P -Value = 0.97), respectively (Table 2). The results of Meta regression showed that the prevalence of myalgia, sore throat, and diarrhea have not any relationship with age and gestational age of pregnant women with COVID 19.
Pooled prevalence of infant characteristics in pregnant women with COVID 19
The least reported prevalence of premature birth in pregnant women with COVID 19 was 8% (95% Cl: 1 - 16%) in the study by Schwartz. et al. and the highest premature birth as prevalence was recorded 50% (95% Cl: 19 - 81%) in the retrospective study by Guo. et al. In total, the pooled prevalence of premature birth has been estimated as 28% (95% Cl: 13 - 43%; I2= 81.57%; P -Value = 0.00) (Figure 5 and Table 3). The results of Meta regression showed that the prevalence of premature birth has not relationship with age (coefficient: -0.014, P: 0.343, 95% CI: -0.044, 0.015), and gestational age of pregnant women with COVID 19 (coefficient: -0.055, P: 0.239, 95% CI: -0.147, 0.036).
The pooled prevalence of intrauterine fetal distress has been estimated as 15% (95% Cl: 4 - 26%; I2= 62.09%; P -Value = 0.04) (Figure 6 and Table 2). The least reported prevalence of intrauterine fetal distress in pregnant women with COVID 19 was 4% (95% Cl: 4 - 13%) in the study by Wang X. et al. and the highest intrauterine fetal distress as prevalence was recorded 30% (95% Cl: 2- 58%) in the retrospective study by Guo. et al (Figure 6 and Table 3). The results of Meta regression showed that the prevalence of intrauterine fetal distress has relationship with age (coefficient: 0.018, P: 0.003, 95% CI: 0.006, 0.030), but has not relationship with gestational age of pregnant women with COVID 19 (coefficient: -0.018, P: 0.851, 95% CI: -0.206, 0.170).
The pooled prevalence of neonatal mortality and lower birth weight in women with COVID 19 were 4% (95% Cl: 1 - 9%; I2= 0.0%; P -Value = 0.52) and 21% (95% Cl: 11 - 31%; I2= 0.0%; P -Value = 0.97), respectively. Also the pooled prevalence of stillbirth was 2% (95% Cl: 1 - 6%; I2= 0.0%; P -Value = 0.40). The Lymphopenia prevalence in in women with COVID 19 were 37% (95% Cl: 17 - 56%; I2= 85.17%; P -Value = 0.00) (Table 3). The results of Meta regression showed that the prevalence of Lymphopenia has not relationship with age (coefficient: 0.029, P: 0.085, 95% CI: -0.004, 0.638), and gestational age of pregnant women with COVID 19 (coefficient: 0.053, P: 0.500, 95% CI: -0.102, 0.209).
Pooled prevalence of Laboratory tests in pregnant women with COVID 19
The pooled prevalence of increase CRP and LFT in women with COVID 19 were 58% (95% Cl: 40 - 75%; I2= 14.13%; P -Value = 0.13) and 32% (95% Cl: 11 - 52%; I2= 0.0%; P -Value = 0.88), respectively (Table 3). The results of Meta regression showed that the prevalence of increase CRP has not relationship with age (coefficient: 0.013, P: 0.440, 95% CI: -0.020, 0.047), and gestational age of pregnant women with COVID 19 (coefficient: -0.052, P: 0.672, 95% CI: -0.293, 0.189).
Pooled prevalence of complications in pregnancy and Cesarean indications in pregnant women with COVID 19
Results of this meta-analysis show that the pooled estimate of preeclampsia and fetal distress in women with COVID 19 were 26% (95% Cl: 3 - 54%; I2= 89.13%; P -Value = 0.00) (Table 4).
Publication Bias Assessment
The results of Egger’s test show no significant bias occurred in the publication of the results (Egger's test = 1.15, SE: 0.480, P = 0.216).