The ‘eligible sample’ comprises 20 248 pregnancies. The mothers of 14 541 (71.8%) pregnancies were recruited antenatally during 1990–92 (recruitment Phase I). Of these 14 541 pregnancies, 68 have no known birth outcome; of the remaining 14 472 pregnancies, 195 were twin, 3 were triplet and 1 was quadruplet, meaning that there are 14 676 known foetuses. These pregnancies resulted in 14 062 live-born children of whom 13 988 were alive at 1 year of age. Post-natal recruitment to the ‘Focus@7’ clinical assessment at the age of ∼7 years recruited a further 456 children from 452 (2.2% of eligible) pregnancies (Phase II). Recruitment during Phase III (ages 8–18 years) added a further 257 children from 254 (1.2% of eligible) pregnancies, giving an overall total of 15 247 (75.3% of eligible) enrolled pregnancies; from these pregnancies there were 14 775 live-born children of which 14 701 were alive at one year of age (Table 1). Table 1ALSPAC eligible sample pregnancy size and birth outcomesALSPAC enrolled pregnancies n = 15 247Non-enrolled pregnancies n = 5001ALSPAC eligible sample n = 20 248 pregnancies
