Feb. 12 (UPI) -- Preliminary findings published Wednesday in The Lancet indicate that COVID-19 may not be passed from mother to child late in pregnancy.
A team at Zhongnan Hospital in Wuhan, China, where the outbreak began, assessed the cases of nine pregnant women in their third trimester of pregnancy who had pneumonia caused by coronavirus.
In six cases, the researchers looked for evidence of intrauterine vertical transmission by testing for coronavirus in amniotic fluid, cord blood and neonatal throat swab samples in the operating room at birth.
All samples tested negative for the virus, which is also known as severe acute respiratory syndrome 2, or SARS-CoV-2.
In the other three cases, the research team reviewed the women's medical records.
All nine were given oxygen support and antibiotics. Six also received antiviral therapy. None of the women in the study developed severe pneumonia or died.
The findings follow a case last week in which a pregnant woman infected with COVID-19 gave birth in Wuhan to a baby who tested positive for the virus a few hours later.
"It is important to note that many important clinical details of this case are missing, and for this reason, we cannot conclude from this one case whether intrauterine infection is possible," Professor Yuanzhen Zhang of the Zhongnan Hospital of Wuhan University and co-author of the Lancet study said in a press release.
All mothers in the study were age 26 to 40; none had underlying health conditions. However, one developed gestational hypertension from week 27 of her pregnancy, and another developed pre-eclampsia at week 31, although both patients' conditions were stable during pregnancy.
In the pregnancies studied, there were two cases of fetal distress, but all nine pregnancies resulted in live births. The researchers also found that symptoms of COVID-19 infection in pregnant women were similar to those reported in non-pregnant women.
"Existing studies into the effects of COVID-19 apply to the general population, and there is limited information about the virus in pregnant women," said co-author Huixia Yang of Peking University First Hospital in China.
"This is important to study because pregnant women can be particularly susceptible to respiratory pathogens and severe pneumonia, because they are immuno-compromised and because of pregnancy-related physiological changes, which could leave them at higher risk of poor outcomes," Yang said. "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."
The authors note that their findings are similar to observations recorded in pregnant women during the severe acute respiratory syndrome, or SARS, in 2002-03. They added that future follow-up of the women and children in the study will be necessary to determine their long-term safety and health.
However, they also caution that their findings are based on a limited number of cases, over a short period of time, and are based only on women who were late in their pregnancy and gave birth by Caesarean section.
It had not been determined whether the virus can be passed from mother to child during vaginal birth.
"We should continue to pay special attentions to newborns born to mothers with COVID-19 pneumonia to help prevent infections in this group," Zhang said.