Interpregnancy interval and adverse birth outcomes: a population-based cohort study of twins.

BACKGROUND: To investigate associations between interpregnancy intervals (IPIs) and adverse birth outcomes in twin pregnancies. METHODS: This retrospective cohort study of 9,867 twin pregnancies in Western Australia from 1980-2015. Relative Risks (RRs) were estimated for the interval prior to the pregnancy (IPI) as the exposure and after the pregnancy as a negative control exposure for preterm birth (< 37 weeks), early preterm birth (< 34 weeks), small for gestational age (SGA: < 10th percentile of birth weight by sex and gestational age) and low birth weight (LBW: birthweight < 2,500 g). RESULTS: Relative to IPIs of 18-23 months, IPIs of < 6 months were associated with a higher risk of early preterm birth (aRR 1.41, 95% CI 1.08-1.83) and LBW for at least one twin (aRR 1.16, 95% CI 1.06-1.28). IPIs of 6-11 months were associated with a higher risk of SGA (aRR 1.24, 95% CI 1.01-1.54) and LBW for at least one twin (aRR 1.09, 95% CI 1.01-1.19). IPIs of 60-119 months and ≥ 120 months were associated with an increased risk of preterm birth (RR 1.12, 95% CI 1.03-1.22; and (aRR 1.25, 95% CI 1.10-1.41, respectively), and LBW for at least one twin (aRR 1.17, 95% CI 1.08-1.28; and aRR 1.20, 95% CI 1.05-1.36, respectively). IPIs of ≥ 120 months were also associated with an increased risk of early preterm birth (aRR 1.42, 95% CI 1.01-2.00). After negative control analysis, IPIs ≥ 120 months remained associated with early preterm birth and LBW. CONCLUSION: Evidence for adverse associations with twin birth outcomes was strongest for long IPIs.

Association between preschooler outdoor play and home yard vegetation as measured by high resolution imagery: Findings from the PLAYCE study.

Outdoor play in the home yard is an important source of physical activity for many preschoolers. This study investigated if home yard size and vegetation are related to preschooler outdoor play time. High-resolution remotely sensed data were used to distinguish between types of vegetation coverage in the home yard. Shrub and tree cover, and yard size, were positively associated with outdoor play. Following stratification by socio-economic status (SES - parent education), only tree cover was positively associated with preschooler outdoor play in low SES households. All types of vegetation cover were positively associated with preschooler outdoor play in higher SES households. This study highlights the importance of larger yard sizes and higher levels of vegetation for facilitating outdoor play in preschoolers.