3.4. Quantitative data synthesis
Because of the high heterogeneity of this study, we used random effects model. Meta-analysis results showed: the incidence of severe case or death was 12%, 95%CI: 0.03~0.20, I2=0%, P =0.006; the incidence of fever was 51%, 95%CI: 0.35~0.67, I2 =89%,P <0.00001; the incidence of cough was 31%, 95%CI: 0.23~0.39,I 2 =38%,P <0.00001; the incidence of lymphopenia was 49%, 95%CI: 0.29~0.70, I2 =83%,P <0.00001; the incidence of positive CT findings was 71%, 95%CI: 0.49~0.93, I2 =90%,P <0.00001; the incidence of coexisting disorders was 33%, 95%CI: 0.21~0.44, I2 =70%,P <0.00001; the incidence of preterm labor was 23%, 95%CI: 0.14~0.32,I2 =21%, P <0.00001; the incidence of cesarean section was 65%, 95%CI: 0.42~0.87,I2 =90%, P <0.00001; the incidence of fetal distress was 29%, 95%CI: 0.08~0.49,I2 =68%, P =0.007; the incidence of neonatal asphyxia or neonatal death or stillbirth was 9%, 95%CI: -0.03~0.21, I2 =0%,P =0.14; the incidence of neonatal infection was 12%, 95%CI: -0.01~0.26, I2 =0%,P =0.06; SARS-CoV-2 test of breast milk was only mentioned in Chen H 2020.2.12, and the incidence was 0, which cannot be calculated by meta-analysis.
To sum up, the P values of neonatal asphyxia or neonatal death or stillbirth and neonatal infection were both greater than 0.05, which have no statistical significance. We couldn’t calculate the incidence of positive SARS-CoV-2 test in breast milk as well. Otherwise the Pvalues in remaining indicators were all less than 0.05, which was statistically significant. The most common clinical features were positive CT findings (71%), cesarean section (65%), and fever (51%), followed by lymphopenia (49%), cough (31%) and severe case or death (12%). Adverse pregnancy outcomes included coexisting disorders (33%), fetal distress (29%) and preterm labor (23%), which was in descending order. Among them, the I2 value of severe case or death was 0%, which was low heterogeneity. Despite the indicator mentioned above was referred to 10 literatures respectively, the incidences of eight documents were all 0 and there were only two none-zero data of the indicator. The I2 value of preterm labor was 21%, which was low heterogeneity. TheI2 value of cough was 38%, which was medium heterogeneity, and the remaining I2 value of indicators ranged from 68% to 90%, which were all high heterogeneity.
Furthermore, we carried out the subgroup analyze based on the data from the fourteen retrospective analyses of COVID-19 infection in pregnant women above and one meta-analysis of epidemiology in all patients infected COVID-19(24). All patients were divided into two subgroups, namely pregnant women and nonpregnant patients. In the fifteen articles, only two indexes, fever and cough, were coincident, which were analyzed in subgroup. The results were as follows. The incidence of fever in pregnant women group was 51%, which were significant lower than 91% in nonpregnant patients group (P <0.00001). The incidence of cough in pregnant women group was also significant lower than nonpregnant patients (31% vs 67%,P <0.0001). The forest plot of subgroup analysis is illustrated in Fig. 1 and Fig. 2.