TOKYO: The proportion of pregnant COVID-19 patients who develop moderate or severe symptoms is approximately twice as high as that of such nonpregnant patients, according a study by Japanese researchers.

The first large-scale study in Japan targeting pregnant women infected with the novel coronavirus was conducted by the National Center for Child Health and Development and others.

The study covered some 4,000 hospitalized female COVID-19 patients aged 15-44 who were registered with a database operated by the National Center for Global Health and Medicine between January 2020 and April 2021. Of them, comparisons were made between 187 pregnant women and 935 nonpregnant women.

Of the pregnant women, 18 suffered moderate or severe symptoms, accounting for 9.6 pct, while the number of such nonpregnant women came to 46, for a share of 4.9 pct.

Of the patients with moderate or severe symptoms, those in 14-27 weeks or later stages of pregnancy accounted for 93.1 pct, indicating that such patients are more prone to develop severer symptoms, compared with those in the early stage of pregnancy.

“The research covered the period before the spread of delta and other coronavirus variants. Still, the outcome is expected to play an important role in considering vaccination and treatments for pregnant women,” an official at the NCCHD noted.