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Researchers are learning more about what pregnant women may experience if they are infected with the coronavirus that causes COVID-19.
Pregnant and recently pregnant women who are diagnosed with COVID-19 in the hospital appear to be less likely to have symptoms of fever and muscle pain but more likely to be admitted to the intensive care unit, according to a new paper published in the BMJ medical journal on Tuesday. The study also found pregnant women with COVID-19 are at increased risk of delivering preterm, but preterm birth rates were not high.
"We found that one in 10 pregnant or recently pregnant women who are attending or admitted to hospital for any reason are diagnosed as having suspected or confirmed COVID-19, although the rates vary," the researchers -- from various institutions in Europe and China -- wrote in the paper.
The researchers reviewed 77 studies on COVID-19 in pregnant and recently pregnant women, published from December 1 and June 26.
Collectively, those studies included data on 13,118 pregnant and recently pregnant women with COVID-19, and 83,486 non-pregnant women of reproductive age who also had COVID-19.
"The COVID-19 related symptoms of fever and myalgia (muscle ache) manifest less often in pregnant and recently pregnant women than in nonpregnant women of reproductive age," the researchers wrote.
"Pregnant or recently pregnant women with COVID-19 seem to be at increased risk of requiring admission to an intensive care unit or invasive ventilation."
Older women, women who are heavier, and women with conditions such as diabetes, kidney disease, or other chronic conditions may also have a higher risk of severe disease, they said.
The researchers also found in those studies that pregnant women with COVID-19 are at increased risk of delivering preterm and their babies being admitted to the neonatal unit, although overall rates of spontaneous preterm births were not high. Also, stillbirth and neonatal death rates were low, the researchers found.
The studies used in the review primarily reported on pregnant women who required visits to the hospital and not many studies reported outcomes by trimester.
"Reviews such as this can only be as good as the studies they summarize and it is important to note that a high proportion of the included studies have a substantial risk of bias," Dr. Marian Knight, professor of maternal and child population health at Britain's University of Oxford, said in a statement distributed by the UK-based Science Media Center on Tuesday.
"It is also important to recognize that, whilst this review reports high preterm birth rates, a number of women affected by COVID-19 in pregnancy are still pregnant, and thus are not included in the study data. This may make preterm birth rates appear artificially high," Knight said. "Nevertheless, some pregnant women affected by COVID-19 may have a subsequent preterm birth, and preventing infection remains essential."
Dr. Edward Morris, president of the Royal College of Obstetricians and Gynecologists, said in another statement on Tuesday that the new paper provides "a welcome and comprehensive synthesis of the available research" on COVID-19 in pregnancy.
"While overall risks to pregnant women from coronavirus are low, the findings of this study highlight the particular risks to pregnant women," Morris said. "Pregnant women are included in the list of people at moderate risk as a precaution and pregnant women should therefore continue to follow the latest government guidance on social distancing and avoiding anyone with symptoms suggestive of coronavirus."