Exposure
The exposure was SGA, defined as sex-specific birthweight
<5th and <3rdpercentiles for gestational age based on a previously established US
birthweight reference for singleton live births (13). We excluded large
for gestational age births (i.e., 90th percentile or
higher) since these fetuses may have different thresholds for labour
tolerance and caesarean delivery risks compared to SGA births. Infants
with birthweight-for-gestational age between the
10-89th percentiles constituted the appropriate for
gestational age (AGA) reference group.