Caesarean birth in women with infertility: population-based cohort study.

OBJECTIVE: Caesarean section (CS) is more common following infertility treatment (IT) but the reasons why remain unclear and confounded. The Robson 10-Group Classification System (TGCS) may further explain variation in CS rates. We assessed the association between mode of conception and CS across Robson groups. DESIGN: Population-based cohort study. SETTING: Ontario, Canada, in a public healthcare system. POPULATION: 921 023 births, 2006-2014. METHODS: Modified Poisson regression produced relative risks (RR) and 95% confidence intervals, comparing the risk of CS among women with (1) subfertility without IT, (2) non-invasive IT (OI, IUI) or (3) invasive IT (IVF)-each relative to (4) spontaneous conception (SC). MAIN OUTCOME MEASURES: CS rate according to one of four modes of conception, overall and stratified by each of the TGCS groups. RESULTS: Relative to SC (26.9%), the risk of CS increased in those with subfertility without IT (RR 1.17, 95% CI 1.16-1.18), non-invasive IT (RR 1.21, 95% CI 1.18-1.24) and invasive IT (RR 1.39, 95% CI 1.36-1.42). Within each Robson group, similar patterns of RRs were seen, but with markedly differing rates. For example, in Group 1 (nulliparous, singleton, cephalic at ≥37 weeks, with spontaneous labour), the respective rates were 15.0, 19.4, 18.7 and 21.9%; in Group 2 (nulliparous, singleton, cephalic at ≥37 weeks, without spontaneous labour), the rates were 35.9, 44.4, 43.2 and 54.1%; and in Group 8 (multiple pregnancy), they were 55.9, 67.5, 65.0 and 69.3%, respectively. CONCLUSIONS: CS is relatively more common in women with subfertility and those receiving IT, an effect that persists across Robson groups. TWEETABLE ABSTRACT: Caesarean delivery is more common in women with infertility independent of demographics and prenatal conditions.

Ski and snowboard school programs: Injury surveillance and risk factors for grade-specific injury.

The objective of our study was to evaluate incidence rates and profile of school program ski and snowboard-related injuries by school grade group using a historical cohort design. Injuries were identified via Accident Report Forms completed by ski patrollers. Severe injury was defined as those with ambulance evacuation or recommending patient transport to hospital. Poisson regression analysis was used to examine the school grade group-specific injury rates adjusting for risk factors (sex, activity, ability, and socioeconomic status) and accounting for the effect of clustering by school. Forty of 107 (37%) injuries reported were severe. Adolescents (grades 7-12) had higher crude injury rates (91 of 10 000 student-days) than children (grades 1-3: 25 of 10 000 student-days; grades 4-6: 65 of 10 000 student-days). Those in grades 1-3 had no severe injuries. Although the rate of injury was lower in grades 1-3, there were no statistically significant grade group differences in adjusted analyses. Snowboarders had a higher rate of injury compared with skiers, while higher ability level was protective. Participants in grades 1-3 had the lowest crude and adjusted injury rates. Students in grades 7-12 had the highest rate of overall and severe injuries. These results will inform evidence-based guidelines for school ski/snowboard program participation by school-aged children.