On March 20, a 28-year-old pregnant woman arrived at Lausanne University Hospital hospital in Switzerland with a fever, fatigue, diarrhea and dry cough. She was given a fever and pain reducer and sent home. Two days later, she returned to the hospital with severe contractions and no improvement in her symptoms. After 10 hours of labor, she gave birth to a stillborn. The cause, researchers believe, was the novel coronavirus.
Early studies of pregnant COVID-19 patients found surprisingly few negative outcomes. But two new case reports documenting stillbirths and maternal deaths have sparked discussion about what the medical community still has to learn.
The two reports, published at the end of last month, are limited in size and scope. Experts cautioned that the most rigorous studies to date suggest little difference in outcomes for pregnant people with COVID-19 and the general population. But the reports do raise questions about what we still don’t know about the virus, nearly months into a global pandemic.
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“There are sort of known unknowns and unknown unknowns,” said Neel Shah, an assistant professor of obstetrics, gynecology and reproductive biology at Harvard Medical School.
“The overwhelming majority of people who are pregnant and become infected do well, as do their babies,” he added. “The challenge… is there are a lot of people who are otherwise healthy, who get suddenly and unpredictably sick, and that's something we don't fully have a handle on yet.”
The Swiss study, published April 30 in the Journal of the American Medical Association, followed one woman from her COVID-19 diagnosis at 19 weeks pregnant through her labor and delivery two days later. The stillbirth, the authors write, “appears related to placental infection with SARS-CoV-2, supported by virological findings in the placenta.” They suggest that the findings warrant further study to see if the coronavirus can cause similar adverse outcomes.
A longer paper, published in the American Journal of Gynecology around the same time, follows nine pregnant women in Iran selected for their known negative outcomes with COVID-19. At the time of publication, seven of the nine women had died, one was critically ill and ventilator-dependent, and one had recovered. None of the women had pre-existing comorbidities, and all had worse outcomes than their other household members.
The researchers argue that, while we still don’t know whether mortality is greater in pregnant people than in the general population, the results should prompt the reinvestigation of any guidelines that “might be potentially construed as providing yet unproven reassurance of the absolute absence of death among pregnant women with COVID-19 disease.”
“The fatal cases reported herein demonstrate [the maternal mortality rate] is not zero, and should inspire caution against complacency and guide restraint in rushing estimates of relative or attributable risk with pregnancy,” they wrote.
But Christopher Zahn, the vice president of practice activities for the American College of Obstetricians and Gynecologists, said the results should be taken with a grain of salt. He pointed to other, larger studies out of New York and China that found no significant difference in outcomes between pregnant people and the general population, and cautioned against “over-concluding” based on select case reports.
“We certainly recognize that pregnant women can get severely ill,” he said. “But what we need to look at from a guidance perspective is the population, not the individual.”
In fact, 16 reports spanning 154 COVID-positive pregnant women and 118 newborns show strikingly few cases of critical outcomes, according to the study published in AJOG. A study of nine pregnant women in Wuhan, China, for example, found that none of the women required mechanical ventilation or respiratory support. A study of 43 pregnant women in New York found that the severity of the disease matched those found in non-pregnant individuals.
The findings are particularly striking given that pregnant people were found to be at greater risk of dying from H1N1, known as swine flu, and SARS, another coronavirus. The low rate of maternal mortality associated with COVID-19, the Iranian researchers wrote, is “unexpected and further inconsistent with data documenting severe disease and death among similarly aged adults who are not pregnant and of low-risk.”
Currently, most major medical associations suggest pregnant people and new parents follow general sanitation protocols, practice social distancing, and wear a face covering if they choose to breastfeed. (Face coverings for infants are not recommended.) Patients with known cases of COVID-19 may have to be separated from their newborn for a period of time to prevent transmission.
Shah said it could be a year before we have accurate data on how exactly the virus affects maternal and fetal outcomes.
“For now, the important thing is we approach this with both humility and empathy,” he said. “We have to be able to update our priors when we get new information.”
“A couple weeks ago, there was no evidence that a mom could pass the virus to a baby, and now there is maybe some evidence,” he added. “What that really means for people who are pregnant and trying to conceive is that they should take extra precautions.”
