September 28, 2020

How does the coronavirus affect pregnancy? Here's what the evidence says.

Daily Briefing

    Not much is known about how the novel coronavirus affects pregnant women, but new studies from CDC and other researchers are shedding some light—and raising questions about whether women infected with the virus are at an increased risk of experiencing adverse pregnancy outcomes.

    3 ways Covid-19 is changing pregnancy for patients and providers

    US new coronavirus cases surpass 7.1 M, deaths top 204K

    The new research comes as U.S. officials as of Monday morning reported a total of 7,139,300 cases of the novel coronavirus virus since the country's epidemic began—up from 7,004,600 cases reported as of Friday morning.

    U.S. officials as of Monday morning also reported a total of 204,597 deaths linked to the coronavirus since the country's epidemic began—up from 202,707 deaths reported as of Friday morning.

    What new research says about how the coronavirus affects pregnant women

    Data from a CDC Morbidity and Mortality Weekly Report published Friday suggested that pregnant women who tested positive for the coronavirus had a higher risk of adverse pregnancy outcomes such as stillbirth and preterm birth when compared with pregnant women who did not test positive for the virus, and that pregnant women may be at a higher risk for developing a severe case of Covid-19, the disease caused by the virus, than nonpregnant women.

    For the report, researchers reviewed data collected from Mach 1 through May 30 on hospitalized patients infected with the novel coronavirus. The researchers identified a total of 105 hospitalized pregnant women who were infected with the virus. According to the researchers, 62 of those women, or 59%, were hospitalized for obstetric reasons, and 43 women, or 41%, were "hospitalized for Covid-19 illness without an obstetric reason."

    The researchers noted that 50 of the 62 pregnant women infected with the coronavirus who had been hospitalized for obstetric reasons, or 81%, did not experiencing symptoms of Covid-19. Among the 43 pregnant women who had been hospitalized for Covid-19, 13, or 30%, required intensive care and six, or 14%, were placed on a ventilator. One of those 43 women died from Covid-19, the researchers said.

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    According to the researchers, pre-pregnancy obesity and gestational diabetes was more common among the pregnant women who were hospitalized for Covid-19 than it was among the pregnant women who were infected with the coronavirus but hospitalized for obstetric reasons.

    The researchers also found that, among 93 of the women who delivered before July 31, 3% experienced stillbirths. According to the researchers, about 15% of the 93 women delivered preterm, and the preterm delivery rate among live births was about 12%. When compared with baseline data, the prevalence of preterm delivery among hospitalized pregnant women who were infected with the coronavirus was about 70% higher than it was among hospitalized pregnant women who were not infected with the pathogen.

    A separate CDC Morbidity and Mortality Weekly Report published Friday focused on 598 pregnant women with confirmed coronavirus infections who were hospitalized between March 1 and Aug. 22. The researchers determined about 55% of pregnant women were not experiencing symptoms of Covid-19 at their time of admission.

    The researchers found that, among the 272 pregnant women who were experiencing symptoms of Covid-19 upon admission, about 16% were admitted to an ICU and 8.5% were treated with mechanical ventilation. Two of the 272 women died, the researchers said. There were no reported ICU admissions, no reported use of mechanical ventilation, and no reported deaths among the asymptomatic pregnant women.

    The researchers noted that 20.6% of the hospitalized pregnant women with Covid-19 had at least one underlying health condition. According to the researchers, asthma was the most commonly reported underlying condition, at about 8%, followed by hypertension, at about 4%.

    The researchers found that 458 of the hospitalized pregnant women infected with coronavirus had completed their pregnancies by the time of discharge. Among those women, 448, or about 98%, experienced live births, while 10 experienced pregnancy loss, which the researchers defined as spontaneous abortion or miscarriage, therapeutic abortion, or stillbirth. The researchers said pregnancy losses occurred among both symptomatic and asymptomatic women.

    The researchers said gestational age was available for 445 of the completed pregnancies. Among those, 87.4% were term births and 12.6% were preterm. Further, the researchers found that, among live births, preterm deliveries were reported for about 23% of symptomatic women and 8% of asymptomatic women. The researchers said that the 12.6% preterm birth rate observed in the study was higher than the 10% preterm birth rate seen "among the general U.S. population in 2018."

    According to the researchers, two newborns died after their birth, and both had been delivered by symptomatic women who had been treated with invasive mechanical ventilation.

    Overall, the researchers said their findings suggest pregnant women experience "disproportionately higher rates of Covid-19–associated hospitalizations compared to nonpregnant women." However, they added, "Although Covid-19 might be more severe in pregnant women, other factors might also explain these higher hospitalization rates." For example, they said, "[p]roviders might have a lower threshold for admitting pregnant women for any reason," and "[s]ome pregnant women with Covid-19 might be admitted solely to give birth." In addition, the researchers said, "[p]regnant women might … have a higher likelihood of being tested for Covid-19 upon admission than do nonpregnant women."

    But a separate study published Wednesday in JAMA found that novel coronavirus infections among pregnant women were not associated with higher rates of adverse pregnancy outcomes.

    For the study, researchers evaluated data on 2,682 people who were in labor at Karolinska University Hospital in Stockholm between March 25 and July 24. The researchers found that 156 of those patients tested positive for the coronavirus during admission and 14 had tested positive for the virus at some point during their pregnancy. According to the researchers, 65% of the pregnant patients who tested positive for the coronavirus during their admission for labor were not experiencing symptoms of Covid-19.

    The researchers compared data on 155 of the patients who tested positive for the virus with corresponding data on 604 patients who were admitted for labor and did not test positive for the coronavirus. They found that about 8% of the patients who were infected with the coronavirus had preeclampsia, compared with about 4% of patients who weren't infected. In addition, the researchers found that patients who had tested positive for the virus were less likely to undergo induced labor, at about 19%, than patients who had tested negative for the virus, at about 30%.

    The researchers wrote that "[o]ther maternal outcomes, including mode of delivery, postpartum hemorrhage, and preterm birth, did not significantly differ between [the] groups."

    However, Mia Ahlberg—the study's lead author; a midwife at Theme Women's Health, Pregnancy and Childbirth, Karolinska University Hospital; and a researcher at the Karolinska Institutet's Department of Medicine—said, "The proportion of women with [Covid-19] symptoms was too small to be able to investigate if these women have a higher risk of complications." She added, "There are several reports of pregnant women who develop severe Covid-19 with adverse outcomes," and "[l]arger studies should be conducted to be able to identify if women with symptoms and different degrees of symptoms constitute a risk group for adverse outcomes such as preterm birth" (Silva, NPR, 9/24; Kelley, "Changing America," The Hill, 9/24; Panagiotakopoulos et al., CDC Morbidity and Mortality Weekly Report, 9/25; Delahoy et al., CDC Morbidity and Mortality Weekly Report, 9/25; Karolinska Institutet, ScienceDaily, 9/23; Ahlberg et al., JAMA, 9/23).

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