To evaluate the association between urinary 8-hydroxy-2'-deoxyguanosine (U8-OHdG) level—a marker of oxidative stress—and the incidence of preterm births (PTBs).

Prospective cohort study.

The Japan Environment and Children’s Study (JECS).

Data from 92 715 women with singleton pregnancies at and after 22 weeks of gestation who were enrolled in the JECS, a nationwide birth cohort study, between 2011 and 2014 were analysed. U8-OHdG levels were assessed once in the second/third trimester using liquid chromatography–tandem mass spectrometry. Participants were categorised into the following three or five groups: low (

Adjusted OR (aOR) for PTB before 37 and 34 weeks of gestation were calculated using a multivariable logistic regression model while adjusting for confounding factors; the moderate or lowest U8-OHdG group was used as the reference, respectively.

The aORs for PTB before 37 weeks of gestation in the high U8-OHdG group were 1.13 (95% CI 1.05 to 1.22) and 1.13 (95% CI 1.04 to 1.23) after stratification. The aOR for PTB before 37 weeks in the fourth group was 0.90 (95% CI 0.81 to 0.99). After stratification, the aORs for PTB before 37 and 34 weeks in the fifth group were 1.15 (95% CI 1.03 to 1.29) and 1.46 (95% CI 1.08 to 1.97), respectively.

High U8-OHdG levels were associated with increased PTB incidence, especially in participants without representative causes for artificial PTB. Our results can help identify the mechanisms leading to PTB, considering the variable aetiologies of this condition; further validation is needed to clarify clinical impacts.

The current endoscopic treatment for postoperative benign hepaticojejunostomy anastomotic stricture (HJAS) has a high technical success rate and is highly effective in the short term. However, long-term results have shown a high rate of stenosis recurrence, which indicates an insufficient response to treatment. Three prospective studies on fully covered self-expandable metallic stent (FC-SEMS) treatment for benign HJAS used the stenosis resolution rate as the primary endpoint, and no study has yet used the long-term non-stenosis rate (at 12 months) as the primary endpoint.

We launched the ‘saddle-cross study’, which will be conducted as a multicentre, prospective intervention of endoscopic treatment using two modified FC-SEMSs (BONASTENT M-Intraductal) that have been improved for benign stenosis in patients with benign HJAS, with the long-term non-restenosis rate (at 12 months) as the primary endpoint. This study aims to evaluate the long-term non-restenosis rate (at 12 months) and safety of the saddle-cross technique for benign HJAS. We plan to enrol 50 participants.

This study has been approved by the Certified Review Board of the National Cancer Center, Japan (CRB3180009). The results will be reported at various conferences and published in international peer-reviewed journals.