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
Blood  Mother: 242 Child: 170 Child:154
Buccal   Child: 662 Child: 446 Child: 316
Newborn screening (Guthrie) card Child: 490
Cord blood Child: 262
Placenta sample Sample: 296
Umbilical cord sample Sample 436
Saliva Child: 316
Faeces   Child: 260
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