Premium
Preterm birth rates in Japan from 1979 to 2014: Analysis of national vital statistics
Author(s) -
Sakata Soyoko,
Konishi Shoko,
Ng Chris Fook Sheng,
Watanabe Chiho
Publication year - 2018
Publication title -
journal of obstetrics and gynaecology research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.597
H-Index - 50
eISSN - 1447-0756
pISSN - 1341-8076
DOI - 10.1111/jog.13460
Subject(s) - medicine , obstetrics , gestation , premature birth , birth rate , singleton , christian ministry , parity (physics) , pediatrics , pregnancy , population , fertility , philosophy , genetics , theology , environmental health , physics , particle physics , biology
Aim Secular trends of preterm birth in Japan between 1979 and 2014 were examined to determine whether changes could be explained by a shift in the distribution of maternal age at delivery and parity and/or by changes in age‐specific preterm birth rates. Methods Live birth data for 1979 to 2014 were obtained from the Japanese Ministry of Health, Labour and Welfare. Analyses were limited to singleton children born in Japan ( n = 43 632 786). Preterm birth was defined using two cut‐offs at < 37 or < 34 weeks of gestation. Crude and standardized rates of preterm birth were calculated for firstborn and later‐born singletons by maternal age at delivery for specific time periods. Results Throughout the study period, the rates of preterm birth (both at < 37 and < 34 weeks of gestation) were higher among mothers aged 20 and younger, and mid‐30s and older, compared to mothers in their 20s or early 30s. The rates of preterm birth at < 37 (but not at < 34) weeks decreased for mothers aged in their late 30s and 40s, and increased for mothers in their 20s and early 30s. Standardized rates of preterm birth showed a secular increase for preterm births at < 37 but not < 34 weeks of gestation. Conclusion The rates of preterm birth among mothers aged in their 20s and early 30s increased between 1979 and 2014, which contributed to the secular increase in rates of preterm birth at < 37 weeks.