Impact of SARS-CoV-2 on intrapartum cardiotocography: a retrospective cohort study

Since the acute respiratory syndrome coronavirus 2 emerged, pregnant women were identified as a vulnerable group. Infection will induce a hypercoagulable state and a proinflammatory response, with a possible cytokine storm. This can be associated with thrombosis and infarction of the placenta. The fetus would have a reactive response to maternal inflammation and fever, reflected in the fetal heart rate changes on the cardiotocography (CTG). Some studies report an increased frequency of CTG abnormalities in pregnant women infected with SARS-CoV-2. The objective of our study was to evaluate frequency of abnormal intrapartum CTG patterns in pregnant infected with SARS-CoV-2.

This retrospective cohort study was conducted at a tertiary hospital center. The exposed group consisted of pregnant women who tested positive for SARS-CoV-2, both symptomatic and asymptomatic were included in the analysis. The control group consisted of randomly selected SARS-CoV-2 negative pregnant women. CTG anomalies were identified according to the physiological interpretation of cardiotocography traces and classified according to the 3-tier system and Royal College of Obstetricians and Gynecologist (RCOG)-system. We compared the frequency of CTG anomalies between SARS-CoV-2 positive pregnant women and controls, and between symptomatic and asymptomatic infections.

We included 119 pregnant women in the case group, of whom 31 were symptomatic (26%), and 116 in the control group. We found no significant differences in maternal and labor characteristics between groups. Statistical analysis showed no significant differences between cases and controls. Perinatal outcomes were similar in the two groups. Major CTG abnormalities were present in 66% of cases versus 72% of controls. Using the three-tier fetal heart rate system, cases and controls can be divided into category I (39 vs. 36%), category II (50 vs. 55%), and category III (12 vs. 9%). CTG characteristics were similar between SARS-CoV-2 positive asymptomatic and symptomatic pregnant women, with no significant differences in the rate of abnormalities.

Unlike suggested in earlier case-series, CTG abnormalities do not seem more frequent in mild or moderate maternal SARS-CoV-2 infection. No specific CTG-abnormalities were found in these fetuses.