Association of maternal nationality with preterm birth and low birth weight rates: analysis of nationwide data in Japan from 2016 to 2020
Maternal Health, Neonatology and Perinatology volume 9, Article number: 3 (2023)
The rate of low birth weight or preterm birth is known to vary according to the birth place of mothers. However, in Japan, studies that investigated the association between maternal nationalities and adverse birth outcomes are few. In this study, we investigated the association between maternal nationalities and adverse birth outcomes.
We obtained live birth data from the Vital Statistics 2016–2020 of the Ministry of Health, Labour, and Welfare. We used data on maternal age, sex, parity, gestational age, birth weight, number of fetuses, household occupation, paternal nationality, and maternal nationality for each infant. We compared the rates of preterm birth and low birth weight at term among mothers whose nationalities were Japan, Korea, China, Philippines, Brazil, and other countries. Log binomial regression model was used to investigate the association between maternal nationality and the two birth outcomes using the other infants’ characteristics as covariates.
In the analysis, data on 4,290,917 singleton births were used. Mothers from Japan, Korea, China, the Philippines, Brazil, and other nations had preterm birth rates of 4.61%, 4.16%, 3.97%, 7.43%, 7.69%, and 5.61%, respectively. The low birth weight rate among Japanese mothers was 5.36% and was the highest among the maternal nationalities. Regression analysis showed that the relative risk for preterm birth among Filipino, Brazilian, and mothers from other countries (1.520, 1.329, and 1.222, respectively) was statistically significantly higher compared with Japanese mothers. In contrast, the relative risk for Korean and Chinese mothers (0.870 and 0.899, respectively) was statistically significantly lower compared with Japanese mothers. Mothers from Korea, China, the Philippines, Brazil, and other nations had a relative risk for low birth weight that was statistically significantly lower than that of Japanese mothers (0.664, 0.447, 0.867, 0.692, and 0.887, respectively).
Support for mothers from the Philippines, Brazil, and other countries are necessary to prevent preterm birth. A future study is necessary to investigate the differences in characteristics among mothers of different nationalities in order to uncover the reason for the high risk for low birth weight among Japanese mothers.
The rates of low birth weight or preterm birth are representative indicators of adverse birth outcomes and had been positively related with neonatal or infant mortality [1, 2]. These rates largely vary among countries [3, 4] and among the birth place of mothers even within the same country [5, 6]. In Japan, the rate of low birth weight or preterm birth is known to vary according to the maternal social characteristics [7,8,9]. However, studies on the association between maternal nationalities and adverse birth outcomes are few in Japan.
Over the recent decades, the number of non-Japanese people in Japan had been increasing , along with the increasing number of births from non-Japanese women . Although the total fertility rate is not high among non-Japanese women, the reported number of births from non-Japanese women in Japan was approximately 20,000 each year . A study has investigated the differences in infant and fetal mortality rates according to the nationality of mothers living in Japan, and the rates among Filipino mothers were high . However, the association of maternal nationalities with the rate of low birth weight or preterm birth has not been investigated. In other countries, many studies on foreign-born or immigrant mothers and adverse birth outcomes found that native-born mothers tended to have lower risk of adverse birth outcomes [5, 6, 13, 14], but the results varied depending on the country or ethnicity [15, 16]. Non-Japanese mothers are known to have some difficulties during the perinatal period in Japan . Knowing the differences in adverse birth outcomes depending on maternal nationality in Japan would enable implementation of preventive measures among the high risk population.
In this study, we investigated the association between maternal nationalities and adverse birth outcomes using the Vital Statistics in Japan.
We used live birth data from the Vital Statistics from 2016 to 2020. The individual-level data were obtained from the Ministry of Health, Labour, and Welfare in Japan. We used data on maternal age, infant’s sex, parity, gestational age, birth weight, number of fetuses, household occupation, paternal nationality, and maternal nationality for each infant. Household occupations were classified as farmer, self-employed, full-time worker 1, full-time worker 2, other occupations, and unemployed. Full-time worker 1 meant workers of a company with < 100 employees, and full-time worker 2 meant public servants and workers or board members of a company with ≥ 100 employees. Japan, Korea, China, Philippines, Brazil, Thailand, the United States, the United Kingdom, Peru, and other countries were available as nationalities of fathers and others in the data. Any combinations of maternal and paternal nationalities between couples were included in the analysis, and non-Japanese couples were also included in the analysis.
We used only singleton births, and illegitimate infants were not included, because paternal nationalities were included in the analysis. Maternal age was grouped into < 20 years, 20–24 years, 25–29 years, 30–34 years (reference), 35–39 years, and ≥ 40 years . Parity was classified into primiparous and multiparous. Births with maternal nationalities from Thailand, the United States, the United Kingdom, and Peru were small in number and were included into the group of other countries in the analysis. Preterm birth was defined as gestational age of ≤ 36 weeks. Low birth weight was defined as < 2,500 g. In this study, the rate of low birth weight at term was calculated according to previous studies [19, 20].
For each maternal nationality, we counted the number of births and the rates of preterm birth and low birth weight by the infants’ characteristics. Log binomial regression model was used to investigate the association between the two birth outcomes and maternal nationality using the other infants’ characteristics (maternal age, infant’s sex, parity, household occupation, paternal nationality) as covariates. The traits of those other infants were included since they may have an impact on results and their distribution may vary based on the nationality of the mother. Log binomial regression model is a regression model used for binary outcome . Relative risk (RR), its 95% confidence interval (CI), and p value were calculated for each maternal nationality; a p value of < 0.05 was judged as statistically significant.
In this study, complete-case analysis was carried out. An imputation utilizing the hot-deck imputation approach was also utilized as a sensitivity analysis . With this technique, a missing value from an observation was substituted with another observation’s value whose values for non-missing variables were comparable to those of the missing value observation. All statistical analyses were conducted using R4.1.3 (https://www.r-project.org/). The statistics shown in this study were processed by the authors using the Vital Statistics data obtained from the Ministry of Health, Labour, and Welfare, and these are different from the statistics published by the Ministry.
Figure 1 shows the flowchart of selection of the study population. After removing cases with missing data, the data of 4,290,917 births were used in the analysis.
Table 1 shows the number of births by the infants’ characteristics and maternal nationality. The largest number of births was from Japanese mothers (4,182,823 births), followed by Chinese mothers (41,041 births).
Table 2 shows the preterm birth rate by the infants’ characteristics and maternal nationality. The preterm birth rate for Chinese women (3.97%) was the smallest among the maternal nationalities. The rates for Filipino and Brazilian mothers were particularly high (7.43% and 7.69%, respectively), compared with those for mothers from the other countries. In addition, the preterm birth rate tended to be high in older mothers and was larger in male infants than in female infants, regardless of maternal nationality.
Table 3 shows the rate of low birth weight at term by the infants’ characteristics and maternal nationality. The low birth weight rate was the highest in Japanese mothers (5.36%) and was the lowest in Chinese mothers (1.90%).
Table 4 shows the results of the regression analysis on the association of maternal nationality with preterm birth and low birth weight at term. Regression analysis showed that the RR for preterm birth among Filipino, Brazilian, and mothers from other countries (1.520, 1.329, and 1.222, respectively) was statistically significantly higher compared with Japanese mothers. In contrast, the relative risk for Korean and Chinese mothers (0.870 and 0.899, respectively) was statistically significantly lower compared with Japanese mothers. For low birth weight, the RR for Korean, Chinese, Filipino, Brazilian, and other countries’ mothers (0.664, 0.447, 0.867, 0.692, and 0.887, respectively) was statistically significantly lower compared with Japanese mothers.
The results of the regression analysis utilizing an imputation method on the relationship between mother nationality and preterm delivery and low birth weight at term are shown in the supplemental table. The results were consistent with the primary analysis.
This study using the Vital Statistics in Japan revealed an association between maternal nationality and adverse birth outcomes. Compared with Japanese women, Filipino, Brazilian, and mothers from other countries had higher risk of preterm birth. On the other hand, the risk for low birth weight at term was higher in Japanese women than in mothers from the other countries. There were possible reasons and implications of the results.
In a previous study, Filipinos in Japan were reported to have the highest infant and fetal mortality rates . A similar high risk among mothers from the Philippines has been observed in Canada and Korea [5, 23]. In addition, in this study, a high risk for preterm birth was observed among mothers from Brazil and other countries. The particularly high proportion of caesarean sections affects the preterm birth rate in Brazil . Additionally, the preterm birth rate was reported to be lower in Japan than the worldwide prevalence  and was higher in Brazil and Philippines than in Japan [26, 27]. Therefore, the difference in preterm birth rates among countries is possibly related with the difference depending on maternal nationalities in Japan. In addition, foreign mothers had been known to have difficulty in understanding health services in Japan or in communicating with others using Japanese language [17, 28]. Moreover, according to an ecological study in Japan, the percentage of non-Japanese nationalities was positively associated with the delay or lack of utilization prenatal care , which is known to be effective for reduction of preterm birth . These factors may explain the high risk in non-Japanese mothers.
In contrast, Korean and Chinese mothers had lower risk, compared with Japanese women. Although the reason for the lower risk is uncertain, the reported preterm birth rates in Korea and China were not higher, compared with that in Japan [5, 31]. In addition, China and Korea are neighboring countries of Japan, and the population of Chinese and Koreans in Japan are higher, compared with that of Filipinos or Brazilians . Therefore, people from these countries might have less psychological stress compared with those from the other countries. Another possible reason is the lower smoking prevalence among women in China and Korea than in Japan [32,33,34]; and a similar difference might exist among mothers in Japan.
Compared with mothers from other nationalities, Japanese women had higher risk of delivering infants of low birth weight. This result was contrary to previous reports that foreign-born or immigrant women tended have adverse birth outcomes in other countries [5, 6, 35]. The estimated worldwide prevalence of low birth weight is higher, compared with the rate in Japan , and non-Japanese mothers have some difficulties in childbirth in Japan. However, the relative risk for low birth weight at term was lower in non-Japanese mothers than in Japanese women. Japanese mothers’ physical traits, such as their low body mass index (BMI) and short stature, is one of the assumed causes, as evidenced by studies conducted in other nations [36,37,38]. Actually, a similar trend of Japanese mothers having higher risk, compared with white mothers or mothers from Korea, China, and the Philippines, was observed in the United States [36, 37]. In addition, the birth weight of infants was reported to be lower in Japanese than in other ethnicities . Possible reasons for the relatively high SGA risk in Japanese mothers had been maternal height, pre-pregnancy weight, and gestational weight gain . In Japan, a low birth weight rate had been known to have an increasing trend from the late twentieth century to the year 2010 [39, 40], and a decrease in birth weight was also observed . Increase in the number of underweight Japanese women has been pointed out as a reason for these birth outcomes . In Japan, a low pre-pregnancy BMI was found to be a major risk factor for low birth weight rate [42, 43]. According to the National Health and Nutrition Survey in 2019, the percentage of underweight (BMI < 18.5) women was 20.7% among the 20–29 years age group and 16.4% among the 30–39 years age group ; these values were higher compared with those reported in Korea and China [45,46,47]. Therefore, the high prevalence of underweight young women in Japan might be one of the reasons for the results of this study.
This study found that women whose nationality was from the Philippines, Brazil, and other countries had relatively high risk of preterm birth rate in Japan. As an implication, unawareness of the available health services in Japan could make consults for prenatal care difficult among non-Japanese women. In that case, more community intervention by public health nurses to connect medical institutions with local non-Japanese residents might be needed. In addition, an epidemiological study on the differences in health behaviors and statuses among maternal nationalities is necessary to uncover the reason for the high risk of low birth weight among Japanese women. Additionally, governments should be aware of the findings about low birth weight since they can make it known to the general population. This could help Japanese women who are expecting to ameliorate their lifestyles. Local governments can also take measures in order for non-Japanese mothers to participate prenatal care or consult a physician. Obstetricians are also advised to be aware of the results because they can speak with both Japanese and non-Japanese moms and warn them of the risks.
There were some limitations in this study. Some major characteristics of pregnant women, such as household income, education level, utilization of prenatal care, and BMI, could not be obtained, because the Vital Statistics data were used in this study. Investigating these factors in a future epidemiological study may help specify the reason for disparities. In addition, period of stay in Japan or Japanese language skill might need to be scrutinized.
This study based on the Vital Statistics in Japan revealed an association between maternal nationality and adverse birth outcomes. The risk for preterm birth was significantly higher in Filipino, Brazilian, and mothers from other countries than in Japanese mothers but was significantly lower in Chinese and Korean mothers than in Japanese mothers. On the other hand, the risk for low birth weight in Japanese mothers was higher, compared with that in mothers from all the other countries.
Availability of data and materials
The data used in this study were obtained from the Ministry of health, Labour, and Welfare in Japan.
Body mass index
Vilanova CS, Hirakata VN, de Souza Buriol VC, Nunes M, Goldani MZ, da Silva CH. The relationship between the different low birth weight strata of newborns with infant mortality and the influence of the main health determinants in the extreme south of Brazil. Popul Health Metr. 2019;17(1):15. https://doi.org/10.1186/s12963-019-0195-7. (PMID:31775758;PMCID:PMC6882357).
García-Basteiro AL, Quintó L, Macete E, Bardají A, González R, Nhacolo A, Sigauque B, Sacoor C, Rupérez M, Sicuri E, Bassat Q, Sevene E, Menéndez C. Infant mortality and morbidity associated with preterm and small-for-gestational-age births in Southern Mozambique: A retrospective cohort study. PLoS One. 2017;12(2):e0172533. https://doi.org/10.1371/journal.pone.0172533. (PMID: 28212393; PMCID: PMC5315372).
Blencowe H, Krasevec J, de Onis M, Black RE, An X, Stevens GA, Borghi E, Hayashi C, Estevez D, Cegolon L, Shiekh S, Ponce Hardy V, Lawn JE, Cousens S. National, regional, and worldwide estimates of low birthweight in 2015, with trends from 2000: a systematic analysis. Lancet Glob Health. 2019;7(7):e849–60. https://doi.org/10.1016/S2214-109X(18)30565-5. (Epub 2019 May 15. PMID: 31103470; PMCID: PMC6560046).
Chawanpaiboon S, Vogel JP, Moller AB, Lumbiganon P, Petzold M, Hogan D, Landoulsi S, Jampathong N, Kongwattanakul K, Laopaiboon M, Lewis C, Rattanakanokchai S, Teng DN, Thinkhamrop J, Watananirun K, Zhang J, Zhou W, Gülmezoglu AM. Global, regional, and national estimates of levels of preterm birth in 2014: a systematic review and modelling analysis. Lancet Glob Health. 2019;7(1):e37–46. https://doi.org/10.1016/S2214-109X(18)30451-0. (Epub 2018 Oct 30. PMID: 30389451; PMCID: PMC6293055).
Song IG, Kim MS, Shin SH, Kim EK, Kim HS, Choi S, Kwon S, Park SM. Birth outcomes of immigrant women married to native men in the Republic of Korea: a population register-based study. BMJ Open. 2017;7(9):e017720. https://doi.org/10.1136/bmjopen-2017-017720. (PMID: 28947460; PMCID: PMC5623517).
Urquia ML, Qiao Y, Ray JG, Liu C, Hjern A. Birth outcomes of foreign-born, native-born, and mixed couples in Sweden. Paediatr Perinat Epidemiol. 2015;29(2):123–30. https://doi.org/10.1111/ppe.12179. (Epub 2015 Feb 14 PMID: 25683170).
Okui T, Nakashima N. Analysis of Differences in Preterm Birth Rates According to Household Occupation in Japan From 2007 to 2019. J Prev Med Public Health. 2022;55(4):371–8. https://doi.org/10.3961/jpmph.22.178. (Epub 2022 Jun 20. PMID: 35940192; PMCID: PMC9371782).
Fujiwara T, Ito J, Kawachi I. Income inequality, parental socioeconomic status, and birth outcomes in Japan. Am J Epidemiol. 2013;177(10):1042–52. https://doi.org/10.1093/aje/kws355. (Epub 2013 Apr 10 PMID: 23576676).
Babazono A, Tsuda T, Amamoto E, Mino Y, Babazono T, Kishi Y, Sigemi J, Ogawa T, Aoyama H. Risk Factors for Low Birth Weight Infants in Japan. J Epidemiol. 1994;4(2):91–8.
Ministry of Justice. Foreign national residents by nationality. Available from: https://www.e-stat.go.jp/stat-search/files?page=1&toukei=00250012&tstat=000001018034. [Cited 07 12 2022].
Yamauchi M. Recent fertility pattern among the immigrant population in Japan. J Popul Probl. 2010;66:41:59. Japanese.
Korekawa Y. An impact of settlements of foreigners on mortality trend; analysis by changing of the foreign population classified by statuses of residence. J Population Stud. 2011;47(1):23 (Japanese).
Acevedo-Garcia D, Soobader MJ, Berkman LF. The differential effect of foreign-born status on low birth weight by race/ethnicity and education. Pediatrics. 2005;115(1):e20–30. https://doi.org/10.1542/peds.2004-1306. (PMID: 15629963).
Vik ES, Aasheim V, Schytt E, Small R, Moster D, Nilsen RM. Stillbirth in relation to maternal country of birth and other migration related factors: a population-based study in Norway. BMC Pregnancy Childbirth. 2019;19(1):5. https://doi.org/10.1186/s12884-018-2140-3.PMID:30611227;PMCID:PMC6321699.
Singh GK, Yu SM. Adverse pregnancy outcomes: differences between US- and foreign-born women in major US racial and ethnic groups. Am J Public Health. 1996;86(6):837–43. https://doi.org/10.2105/ajph.86.6.837.PMID:8659659;PMCID:PMC1380404.
Flores ME, Simonsen SE, Manuck TA, Dyer JM, Turok DK. The “Latina epidemiologic paradox”: contrasting patterns of adverse birth outcomes in U.S.-born and foreign-born Latinas. Womens Health Issues. 2012;22(5):e501–7. https://doi.org/10.1016/j.whi.2012.07.005. (PMID: 22944904).
Kita S, Minatani M, Hikita N, Matsuzaki M, Shiraishi M, Haruna M. A Systematic Review of the Physical, Mental, Social, and Economic Problems of Immigrant Women in the Perinatal Period in Japan. J Immigr Minor Health. 2015;17(6):1863–81. https://doi.org/10.1007/s10903-015-0192-2. (PMID: 25784144).
Kim YN, Choi DW, Kim DS, Park EC, Kwon JY. Maternal age and risk of early neonatal mortality: a national cohort study. Sci Rep. 2021;11(1):814. https://doi.org/10.1038/s41598-021-80968-4.PMID:33436971;PMCID:PMC7804272.
Yorifuji T, Kashima S, Doi H. Outdoor air pollution and term low birth weight in Japan. Environ Int. 2015;74:106–11. https://doi.org/10.1016/j.envint.2014.09.003. Epub 2014 Oct 22. Erratum in: Environ Int. 2015;78:95–6.
Auger N, Luo ZC, Platt RW, Daniel M. Do mother’s education and foreign born status interact to influence birth outcomes? Clarifying the epidemiological paradox and the healthy migrant effect. J Epidemiol Community Health. 2008;62(5):402–9. https://doi.org/10.1136/jech.2007.064535.PMID:18413452.yorifujioutdoorairpollution.
Chen W, Shi J, Qian L, Azen SP. Comparison of robustness to outliers between robust poisson models and log-binomial models when estimating relative risks for common binary outcomes: a simulation study. BMC Med Res Methodol. 2014;26(14):82. https://doi.org/10.1186/1471-2288-14-82. (PMID:24965498;PMCID:PMC4079617).
Kowarik A, Templ M. Imputation with the R Package VIM. J Stat Softw. 2016;74(7):1–16.
Bartsch E, Park AL, Jairam J, Ray JG. Concomitant preterm birth and severe small-for-gestational age birth weight among infants of immigrant mothers in Ontario originating from the Philippines and East Asia: a population-based study. BMJ Open. 2017;7(7):e015386. https://doi.org/10.1136/bmjopen-2016-015386. (PMID: 28720616; PMCID: PMC5734583).
Barros FC, RabelloNeto DL, Villar J, Kennedy SH, Silveira MF, Diaz-Rossello JL, Victora CG. Caesarean sections and the prevalence of preterm and early-term births in Brazil: secondary analyses of national birth registration. BMJ Open. 2018;8(8):e021538. https://doi.org/10.1136/bmjopen-2018-021538. (PMID: 30082353; PMCID: PMC6078248).
Walani SR. Global burden of preterm birth. Int J Gynaecol Obstet. 2020;150(1):31–3. https://doi.org/10.1002/ijgo.13195. (PMID: 32524596).
Ferreira ÉK, de Almeida MF, Alencar GP, da Silva ZP. Live births of immigrant mothers in Brazil: A population-based study. J Migr Health. 2022;20(5):100108. https://doi.org/10.1016/j.jmh.2022.100108. (PMID: 35592862; PMCID: PMC9112019).
World Health Organization. Born too soon: the global action report on preterm birth: World Health Organization; 2012. Available from: https://apps.who.int/iris/handle/10665/44864. [Cited 07 12 2022].
Hashimoto H, Ito K, Yamaji Y, Sasaki Y, Murashima S, Yanagisawa S. Difficulties of pregnancy, delivery, and child raising for immigrant women in Japan and their strategies for overcoming them. Kokusai Hoken Iryo (J Int Health). 2011;26(4):281–93. Japanese.
Osawa E, Kodama T. Regional socio-environmental characteristics associated with inadequate prenatal care during pregnancy: an ecological study of 47 prefectures in Japan. BMC Pregnancy Childbirth. 2021;21(1):619. https://doi.org/10.1186/s12884-021-04100-0. (PMID:34517823;PMCID:PMC8439025).
Vintzileos AM, Ananth CV, Smulian JC, Scorza WE, Knuppel RA. The impact of prenatal care in the United States on preterm births in the presence and absence of antenatal high-risk conditions. Am J Obstet Gynecol. 2002;187(5):1254–7. https://doi.org/10.1067/mob.2002.127140. (PMID: 12439515).
Song Q, Chen J, Zhou Y, Li Z, Li H, Liu J. Preterm delivery rate in China: a systematic review and meta-analysis. BMC Pregnancy Childbirth. 2022;22(1):383. https://doi.org/10.1186/s12884-022-04713-z.PMID:35501738;PMCID:PMC9063297.
Chang Y, Kang HY, Lim D, Cho HJ, Khang YH. Long-term trends in smoking prevalence and its socioeconomic inequalities in Korea, 1992–2016. Int J Equity Health. 2019;18(1):148. https://doi.org/10.1186/s12939-019-1051-x. (PMID:31533732;PMCID:PMC6751588).
Reitsma MB, Flor LS, Mullany EC, Gupta V, Hay SI, Gakidou E. Spatial, temporal, and demographic patterns in prevalence of smoking tobacco use and initiation among young people in 204 countries and territories, 1990–2019. Lancet Public Health. 2021;6(7):e472–81. https://doi.org/10.1016/S2468-2667(21)00102-X. (Epub 2021 May 28. PMID: 34051921; PMCID: PMC8251503).
Tomioka K, Kurumatani N, Saeki K. The Association Between Education and Smoking Prevalence, Independent of Occupation: A Nationally Representative Survey in Japan. J Epidemiol. 2020;30(3):136–42. https://doi.org/10.2188/jea.JE20180195. (Epub 2019 Mar 2. PMID: 30828035; PMCID: PMC7025916).
Behboudi-Gandevani S, Bidhendi-Yarandi R, Panahi MH, Mardani A, Paal P, Prinds C, Vaismoradi M. Adverse Pregnancy Outcomes and International Immigration Status: A Systematic Review and Meta-analysis. Ann Glob Health. 2022;88(1):44. https://doi.org/10.5334/aogh.3591. (PMID:35854922;PMCID:PMC9248985).
Morisaki N, Kawachi I, Oken E, Fujiwara T. Parental Characteristics can Explain Why Japanese Women Give Birth to the Smallest Infants in the United States. Paediatr Perinat Epidemiol. 2016;30(5):473–8. https://doi.org/10.1111/ppe.12308. (Epub 2016 May 30. PMID: 27240939; PMCID: PMC4970883).
Yusuf KK, Dongarwar D, Alagili DE, Maiyegun SO, Salihu HM. Temporal trends and risk of small for gestational age (SGA) infants among Asian American mothers by ethnicity. Ann Epidemiol. 2021;63:79–85. https://doi.org/10.1016/j.annepidem.2021.07.004. (Epub 2021 Jul 24 PMID: 34314846).
Morisaki N, Kawachi I, Oken E, Fujiwara T. Social and anthropometric factors explaining racial/ethnical differences in birth weight in the United States. Sci Rep. 2017;21(7):46657. https://doi.org/10.1038/srep46657.PMID:28429791;PMCID:PMC5399358.
Mine T, Tsuboi S, Fukushima, F. Twenty-year trends of low birth weight in japan: a joinpoint regression analysis of data from 2000 to 2019. Front Reprod Health. 2021;3:772575. https://doi.org/10.3389/frph.2021.772575.
Takemoto Y, Ota E, Yoneoka D, Mori R, Takeda S. Japanese secular trends in birthweight and the prevalence of low birthweight infants during the last three decades: A population-based study. Sci Rep. 2016;9(6):31396. https://doi.org/10.1038/srep31396. (PMID:27503177;PMCID:PMC4977558).
Kato N, Sauvaget C, Yoshida H, Yokoyama T, Yoshiike N. Factors associated with birthweight decline in Japan (1980–2004). BMC Pregnancy Childbirth. 2021;21(1):337. https://doi.org/10.1186/s12884-021-03819-0. (PMID:33906616;PMCID:PMC8080357).
Murai U, Nomura K, Kido M, Takeuchi T, Sugimoto M, Rahman M. Pre-pregnancy body mass index as a predictor of low birth weight infants in Japan. Asia Pac J Clin Nutr. 2017;26(3):434–7. https://doi.org/10.6133/apjcn.032016.11. (PMID: 28429908).
Suzuki K, Nomura K, Takenoshita S, Ando K, Kido M. Combination of parity and pre-pregnancy BMI and low birth weight infants among Japanese women of reproductive age. Ind Health. 2016;54(6):515–20. https://doi.org/10.2486/indhealth.2016-0088. (Epub 2016 Jul 29. PMID: 27476380; PMCID: PMC5136608).
Ministry of Health, Labour, and Welfare. National health and nutrition survey. Available from: https://www.e-stat.go.jp/stat-search/files?page=1&toukei=00450171&tstat=000001041744. [Cited 07 12 2022].
Shin HY, Kang HT. Recent trends in the prevalence of underweight, overweight, and obesity in Korean adults: The Korean National Health and Nutrition Examination Survey from 1998 to 2014. J Epidemiol. 2017;27(9):413–9. https://doi.org/10.1016/j.je.2016.08.014. (Epub 2017 Apr 15. Erratum in: J Epidemiol. 2018 Feb 5;28(2):105. PMID: 28420559; PMCID: PMC5565760).
He Y, Pan A, Yang Y, Wang Y, Xu J, Zhang Y, Liu D, Wang Q, Shen H, Zhang Y, Yan D, Peng Z, Hu FB, Ma X. Prevalence of Underweight, Overweight, and Obesity Among Reproductive-Age Women and Adolescent Girls in Rural China. Am J Public Health. 2016;106(12):2103–10. https://doi.org/10.2105/AJPH.2016.303499. (PMID:27831775;PMCID:PMC5105028).
Wang M, Xu PS, Liu W, Zhang C, Zhang X, Wang L, Liu J, Zhu Z, Hu J, Luo PX, Wang PW. Prevalence and changes of BMI categories in China and related chronic diseases: Cross-sectional National Health Service Surveys (NHSSs) from 2013 to 2018. EClinicalMedicine. 2020;11(26):100521. https://doi.org/10.1016/j.eclinm.2020.100521. (PMID: 32984787; PMCID: PMC7492818).
Part of the study was supported by JSPS KAKENHI Grant Number JP22K17372.
Ethics approval and consent to participate
All methods were carried out in accordance with relevant guidelines and regulations.
All experimental protocols were approved by an ethical committee of Kyushu University (No. 22221–00). In addition, the need for informed consent was waived by the ethical committee of Kyushu University.
Consent for publication
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
About this article
Cite this article
Okui, T., Sato, Y., Morokuma, S. et al. Association of maternal nationality with preterm birth and low birth weight rates: analysis of nationwide data in Japan from 2016 to 2020. matern health, neonatol and perinatol 9, 3 (2023). https://doi.org/10.1186/s40748-023-00149-1