Figure 1 .

Fixed cohort bias. Black shows the available birth cohort data, with births spanning 1 2000– 30 November 2019. Yellow indicates the conception dates included in the birth cohort. Pink indicates the conception dates we would like to include to prevent fixed-cohort bias. At the beginning of the study period, longer gestations are disproportionately represented, and at the end only shorter gestations are included, as birth must take place prior to 30 November 2019, the end of available birth record data