A total of 460 pregnant women tested positive for the novel coronavirus in Tokyo between April 2020 to July this year, with the highest monthly figure of 98 logged last month, a survey conducted by a university hospital director showed Monday.

The study, compiled by Nippon Medical School Tamanagayama Hospital director Akihito Nakai, follows the case of a COVID-19 positive pregnant woman in Kashiwa, Chiba Prefecture, who was unable to find a hospital that would admit her and lost her baby after going into labor prematurely and giving birth at home.

The incident has underscored the strain on hospitals due to the explosive spread of COVID-19.

While there have been calls to improve measures for women in similar positions, there is currently no nationwide data on the number of pregnant women infected with the virus.

"In order to improve the medical system, it is necessary to grasp the true state of infection among pregnant women," Nakai said.

The survey, which compiled preliminary monthly figures provided by the Tokyo metropolitan government, found that from April last year to June this year, infections among pregnant women stood at around 3 to 50 per month but increased sharply to 98 in July.

The actual number of infections is believed to be even higher, as asymptomatic or mild cases of the virus are likely not included.

Of the 460 pregnant women reported as COVID-19 positive during that period, 438 were hospitalized, while 22 chose to recuperate at home for reasons such as child care. Around 79 percent, or 61, of the 77 who gave birth while infected had their baby delivered via cesarean section.

Pregnant women accounted for 0.21 percent of the total number of infections in Tokyo as of July, lower than the 0.62 percent they represent of the general population.

"Appropriate infection control measures have kept the rate of infection among pregnant women low. I hope pregnant women and their families get vaccinated so that we can continue to prevent infections," Nakai said.

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