Wave W1 W2 W3 W4 W5 W6
Time of collection Up to 12 weeks gest 13 to 24 weeks gest 25 weeks to birth Birth 18 mths 6 yrs
Year 2007-2009 2007-2009 2007-2009 2007-2009 2008-2011 2014-2016
Birth weight P:SDVM F P:SDVC
Birth length P:SDVC
Birth head circumference P:SDVC
Gestational age P:SDVM F P:SDVC
Mode of delivery P:SDVM
Multiple births P:SDVM F  P:SDVC
Labour  P:SDVM
Dates and times of birth  P:SDVC
Intensive care  P:SDVC
Placental examination (weight, cord insertion, chorionicity) P:SDVC
Twin status (zygosity, chorionicity, amnionicity) P:SDVC
S – self report
P – parent report
C – child report
T – teacher report
N – welfare nurse
O – observation
XM: Mother
XF/P: Father/partner
XC: Child
XS: Sibling
XG: Grandparent

SDV: Study Devised Variable