Association of premarital pregnancy with adverse birth outcomes and its characteristics in Japan
Abstract Background A study investigating the association between premarital pregnancy and the adverse birth outcomes has not been conducted in Japan. This study aimed to investigate an association of premarital pregnancy with adverse birth outcomes and its characteristics in Japan, using national b...
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BMC
2025-04-01
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| Series: | Contraception and Reproductive Medicine |
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| Online Access: | https://doi.org/10.1186/s40834-025-00357-4 |
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| author | Tasuku Okui Naoki Nakashima |
| author_facet | Tasuku Okui Naoki Nakashima |
| author_sort | Tasuku Okui |
| collection | DOAJ |
| description | Abstract Background A study investigating the association between premarital pregnancy and the adverse birth outcomes has not been conducted in Japan. This study aimed to investigate an association of premarital pregnancy with adverse birth outcomes and its characteristics in Japan, using national birth data. Methods Birth data from the Vital Statistics: Occupational and Industrial Aspects for the fiscal years 2010, 2015, and 2020 were used. Firstborn and singleton births were used, and we restricted the data to infants born to Japanese parents. We defined the status of premarital pregnancy based on the length of marriage at the time of birth. Rates of preterm birth, term low birth weight (TLBW), and small-for-gestational-age (SGA) were used as outcomes. Log-binomial regression analysis was conducted to calculate the adjusted risk ratio of premarital pregnancy for each of the outcomes. Furthermore, logistic regression analysis was conducted to identify factors associated with premarital pregnancy. Results Data from 888,459 births were included in the analysis. The results of log-binomial regression showed that the risk of premarital pregnancy was statistically significantly higher than that of postmarital pregnancy for all the outcomes, and the risk ratios were 1.65 (95% confidence intervals (CI):1.58, 1.72), 1.17 (95% CI:1.12, 1.22), and 1.12 (95% CI:1.08, 1.17) for preterm birth, TLBW, and SGA, respectively. The results of logistic regression analysis showed that lower non-manual workers, manual workers, and others were significantly and positively associated with premarital pregnancy compared to upper non-manual workers in terms of maternal and paternal occupations. Conclusions It was shown that premarital pregnancy was associated with a higher risk of preterm birth, TLBW, and SGA and was positively associated with parental occupations such as lower non-manual workers and manual workers in Japan. |
| format | Article |
| id | doaj-art-0a016a8c20a94e36989bbaecedcc4532 |
| institution | OA Journals |
| issn | 2055-7426 |
| language | English |
| publishDate | 2025-04-01 |
| publisher | BMC |
| record_format | Article |
| series | Contraception and Reproductive Medicine |
| spelling | doaj-art-0a016a8c20a94e36989bbaecedcc45322025-08-20T02:17:04ZengBMCContraception and Reproductive Medicine2055-74262025-04-011011810.1186/s40834-025-00357-4Association of premarital pregnancy with adverse birth outcomes and its characteristics in JapanTasuku Okui0Naoki Nakashima1Medical Information Center, Kyushu University HospitalMedical Information Center, Kyushu University HospitalAbstract Background A study investigating the association between premarital pregnancy and the adverse birth outcomes has not been conducted in Japan. This study aimed to investigate an association of premarital pregnancy with adverse birth outcomes and its characteristics in Japan, using national birth data. Methods Birth data from the Vital Statistics: Occupational and Industrial Aspects for the fiscal years 2010, 2015, and 2020 were used. Firstborn and singleton births were used, and we restricted the data to infants born to Japanese parents. We defined the status of premarital pregnancy based on the length of marriage at the time of birth. Rates of preterm birth, term low birth weight (TLBW), and small-for-gestational-age (SGA) were used as outcomes. Log-binomial regression analysis was conducted to calculate the adjusted risk ratio of premarital pregnancy for each of the outcomes. Furthermore, logistic regression analysis was conducted to identify factors associated with premarital pregnancy. Results Data from 888,459 births were included in the analysis. The results of log-binomial regression showed that the risk of premarital pregnancy was statistically significantly higher than that of postmarital pregnancy for all the outcomes, and the risk ratios were 1.65 (95% confidence intervals (CI):1.58, 1.72), 1.17 (95% CI:1.12, 1.22), and 1.12 (95% CI:1.08, 1.17) for preterm birth, TLBW, and SGA, respectively. The results of logistic regression analysis showed that lower non-manual workers, manual workers, and others were significantly and positively associated with premarital pregnancy compared to upper non-manual workers in terms of maternal and paternal occupations. Conclusions It was shown that premarital pregnancy was associated with a higher risk of preterm birth, TLBW, and SGA and was positively associated with parental occupations such as lower non-manual workers and manual workers in Japan.https://doi.org/10.1186/s40834-025-00357-4JapanPremarital pregnancyPreterm birthSmall-for-gestational-ageLow birth weight |
| spellingShingle | Tasuku Okui Naoki Nakashima Association of premarital pregnancy with adverse birth outcomes and its characteristics in Japan Contraception and Reproductive Medicine Japan Premarital pregnancy Preterm birth Small-for-gestational-age Low birth weight |
| title | Association of premarital pregnancy with adverse birth outcomes and its characteristics in Japan |
| title_full | Association of premarital pregnancy with adverse birth outcomes and its characteristics in Japan |
| title_fullStr | Association of premarital pregnancy with adverse birth outcomes and its characteristics in Japan |
| title_full_unstemmed | Association of premarital pregnancy with adverse birth outcomes and its characteristics in Japan |
| title_short | Association of premarital pregnancy with adverse birth outcomes and its characteristics in Japan |
| title_sort | association of premarital pregnancy with adverse birth outcomes and its characteristics in japan |
| topic | Japan Premarital pregnancy Preterm birth Small-for-gestational-age Low birth weight |
| url | https://doi.org/10.1186/s40834-025-00357-4 |
| work_keys_str_mv | AT tasukuokui associationofpremaritalpregnancywithadversebirthoutcomesanditscharacteristicsinjapan AT naokinakashima associationofpremaritalpregnancywithadversebirthoutcomesanditscharacteristicsinjapan |