Table 1

Basic characteristics of the study population (1991–1997 cohort n=21 897, combined cohort n=52 220)

1991–1997 cohort (n=21 897)Combined cohort (n=52 220)
CountPer centCountPer cent
Sex of child
 Female10 31947%25 01748%
 Male11 57853%27 20352%
Maternal race
 Chinese10 48548%22 24843%
 Indian281113%854316%
 Malay762135%16 00631%
 Others9804%542310%
Gestational term
 Extremely preterm310%1220%
 Very preterm1661%4281%
 Moderately preterm2141%4751%
 Late preterm13686%35067%
 Early term652330%18 59336%
 Full term10 93150%25 04048%
 Late term212810%33936%
 Post-term5362%6631%
Maternal age in years (mean=30; SD=5)
 <26421619%
 26~30848639%
 31~35672931%
 >35246611%
Maternal height in cm (mean=156; SD=6)
 <151355516%
 151~155660630%
 156~160739534%
 >160434120%
Household income
 <$1500609228%
 $1500~$3000717033%
 >$3000863539%