In the 2010 cohort, also presented in Table 2, we observed the same trend of better child health at the age of 18 months according to older maternal age as we observed in the 2001 cohort: ptrend<0.01 for unintentional injuries and ptrend = 0.05 for hospital admission. Although the lower risk for hospital admission among older maternal age groups was not statistically significant, the odds ratios were highly consistent between the 2001 and 2010 cohorts. We did not observe much change in the odds ratios after additionally accounting for preterm births and birthweight. In the follow-up analyses, we stratified the sample by maternal parity. Examining the odds ratios obtained with the sub-samples of parity 1 and parity 2, we did not see much deviation from the original analyses in the magnitude and direction of associations. We present the results in S2 Table.