{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,22]],"date-time":"2026-01-22T12:16:17Z","timestamp":1769084177312,"version":"3.49.0"},"reference-count":61,"publisher":"Public Library of Science (PLoS)","issue":"1","license":[{"start":{"date-parts":[[2026,1,21]],"date-time":"2026-01-21T00:00:00Z","timestamp":1768953600000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["www.plosone.org"],"crossmark-restriction":false},"short-container-title":["PLoS One"],"abstract":"<jats:sec id=\"sec001\">\n                    <jats:title>Objectives<\/jats:title>\n                    <jats:p>A study investigating the impact of COVID-19 on birth rates across women\u2019s age groups has not been previously conducted in Japan. Therefore, we examined this issue using national birth data.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec id=\"sec002\">\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>The analysis utilized monthly live birth data from the Vital Statistics from 2015 to 2023, which were accessed on July 27, 2025. We estimated the expected number of births in the post-pandemic period through quasi-Poisson regression analysis and calculated the ratios of the sum of actual births to that of predicted births for each women\u2019s age group. In addition, a segmented regression analysis was performed to assess the effect of the pandemic on birth rates, focusing on changes in level and trend across age groups.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec id=\"sec003\">\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>The ratios of the sum of actual births to that of predicted births in the post-pandemic period was close to one overall, but actual numbers were significantly lower than predicted numbers in women aged 15\u201319, 20\u201324, 25\u201329, and 35\u201339 years. Segmented regression analysis revealed significant declines in birth rates among women aged 15\u201319, 20\u201324, and 45\u201349 years due to the pandemic, with the rate ratios (RRs) being 0.880 (95% confidence interval (CI): 0.828, 0.935), 0.936 (95%CI: 0.907, 0.967), and 0.890 (95%CI: 0.824, 0.961), respectively, indicating that an immediate effect of the pandemic was evident in those age groups. In addition, significant trend changes were observed among women aged 20\u201324, 25\u201329, 35\u201339, and 45\u201349 years, with the RRs being 0.995 (95%CI: 0.993, 0.996), 0.998 (95%CI: 0.996, 0.999), 0.998 (95%CI: 0.997, 1.000), and 1.004 (95%CI: 1.001, 1.008), respectively, indicating an acceleration of the declining trend in some age groups.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec id=\"sec004\">\n                    <jats:title>Conclusions<\/jats:title>\n                    <jats:p>These findings suggest that the pandemic\u2019s effect on birth rates varies by women\u2019s age, with a more pronounced decrease among younger women.<\/jats:p>\n                  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