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.

BackgroundThe objective is to examine the association between AD and the daily number of medical consultations for pollinosis in Fukuoka City.MethodsWe analyzed 65,488 daily medical consultations for pollinosis from 4 clinics in Fukuoka City from February to April, 1989–2012. Time-series analyses were performed to estimate the clinic-specific relative risk (RR) of clinical pollinosis associated with AD, adjusting for airborne pollen, suspended particulate matter (SPM), meteorological and temporal factors. Delayed effects were considered. The association with SPM was also examined given its relationship with AD. The clinic-specific RRs were combined using meta-analytic technique.ResultsAD on the same day (lag 0) and the previous 3 to 5 days (lags 3, 4, and 5) was positively associated with the risk of medical consultations for pollinosis. Clinic visits were 21.5% (95% confidence interval 3.1% – 43.1%) higher when there was an AD event (across lags 0–5). The association with SPM showed comparable lag structure, but with smaller effect estimates. When stratified by the occurrence of AD, the estimated risk increases associated with SPM did not differ between the AD-affected and AD-free days.ConclusionAD is associated with an increased risk of medical consultations for pollinosis in spring. More research is needed to elucidate the roles of air particles with different sizes.Electronic supplementary materialThe online version of this article (doi:10.1186/s12199-017-0623-x) contains supplementary material, which is available to authorized users.

To examine whether a longer time to pregnancy is associated with preterm births distinguished as either spontaneous or indicated delivery. Methods: A cross-sectional survey was conducted targeting parous women aged 20-44 years old residing across Japan whose first-born children were singletons. Information on reproductive history including time to pregnancy (TTP) and use of assisted reproductive technology (ART) was collected using internet-based questionnaire. A delivery was judged spontaneous if the mother had either labor and/or membrane rupture at hospital admission. Multinomial logistic regression analyses were performed to estimate odds ratios and 95% confidence intervals (CI) for spontaneous and indicated preterm birth at ＜ 34 or at ＜ 37 weeks of gestation while adjusting for potential confounders. Results: The analytic sample was n=4,208 mothers with first-born singletons. After adjusting for age, use of ART, and other possible confounders, women with TTP of 12＋ months had significantly higher odds of spontaneous preterm birth at ＜ 34 weeks (OR 4.55, 95% CI 1.10-18.77) but not at ＜ 37 weeks (OR 1.07, 95% CI 0.65-1.75), compared to those with TTP of ＜ 6 months. Women with unknown TTP tended to have higher odds of spontaneous preterm birth at ＜ 34 weeks (OR 3.67, 95% CI 1.02-13.19) and at ＜ 37 weeks (OR 1.38, 95% CI 0.98-1.96), though not statistically significant. There was no significant association with TTP and indicated preterm birth. Conclusions: Compared to mothers with shorter TTP, those with longer TTP are more likely to experience spontaneous preterm birth.

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