Can Coronavirus Pass From Pregnant Women to Infants?

Since the novel coronavirus (COVID-19) has emerged, there has been an urgent effort to understand the clinical characteristics of infection. Medical journals have rapidly published information including the epidemiological details of the first 425 patients with COVID-19 and a close look at a patient cohort located outside the city of Wuhan.

Pregnant women are at increased risk for severe pneumonia and respiratory infection due to immunosuppression. In some cases, respiratory infections can lead to birth complications. For example, a study of pregnant women who were hospitalized with influenza found a substantially higher preterm birth rate than that of the general population.

The investigators of a new study, published in The Lancet, have advanced the understanding of the impact COVID-19 infection could have on pregnancy. The article detailed clinical characteristics and potential for intrauterine vertical transmission in a cohort of 9 pregnant women who developed COVID-19 pneumonia late in their pregnancies.

The study team found that clinical characteristics of COVID-19 pneumonia in pregnant women were similar to those reported for adults who are not pregnant. The investigators also reported that in this small group of cases there was no evidence of intrauterine infection caused by vertical transmission.

The study was conducted by retrospective review of laboratory results, health records, and chest CT scans. The 9 women were admitted to Zhongnan Hospital of Wuhan University, in Wuhan, China, the epicenter of the outbreak. Admissions took place from January 20 to January 31, 2020.

Intrauterine vertical transmission was assessed in 6 of the 9 patients by testing cord blood, amniotic fluid, and neonatal throat swabs. Breastmilk samples were also tested.

The symptoms of the 9 individuals were similar to those seen in the general population. Fever was present in 7 patients, cough in 4 patients, myalgia in 3 patients, malaise in 2 patients, and sore throat in 2 patients.

Increased aminotransferase concentrations were observed in 3 patients. Lymphopenia occurred in 5 patients and fetal distress monitoring was required in 2 patients. None of the patients advanced to severe COVID-19 pneumonia or died as of February 4, 2020.

Livebirths via caesarean section were recorded for all 9 patients. The 9 infants had Appearance, Pulse, Grimace, Activity, Respiration scores of 8-9 within 1 minute and scores of 9-10 5 minutes after birth.

Among the 6 patients for whom intrauterine vertical transmission was assessed by amniotic fluid, cord blood, and neonatal throat swab, all samples tested negative for the virus.

Despite a small sample size, the study offers important information on the vertical transmission potential of COVID-19 in pregnant women.

"Findings from this small group of cases suggest that there is currently no evidence for intrauterine infection caused by vertical transmission in women who develop COVID-19 pneumonia in late pregnancy," study authors wrote.

Areas of future study identified by the investigators include whether acquisition of the virus earlier in pregnancy impacts vertical transmission, if vaginal delivery increases risk of intrapartum transmission, and whether COVID-19 damages the placenta.

"This is important to study because pregnant women can be particularly susceptible to respiratory pathogens and severe pneumonia, because they are immunocompromised and because of pregnancy-related physiological changes which could leave them at higher risk of poor outcomes. Although in our study no patients developed severe pneumonia or died of their infection, we need to continue to study the virus to understand the effects in a larger group of pregnant women," said study author Huixia Yang, MD, Director of the Department of Obstetrics and Gynecology, Peking University First Hospital, in a press release.

While more research will be necessary, it is substantial that the virus did not pass on from mother to child in this patient group.