Characteristics of children with or without PCHI by age 11 years
| Children with PCHI | Children without PCHI | |
| n=44 | n=19 460 | |
| Mean gestational length, weeks (95% CI)* | 38.7 (37.4 to 40.0) | 39.3 (39.2 to 39.3) |
| Missing (n) | 3 | 941 |
| Mean birth weight, z-score (95% CI) | −0.2 (−0.5 to 0.2) | 0.0 (0.0 to 0.0) |
| Missing (n) | 3 | 941 |
| Sex (n, %) | ||
| Male | 22 (47.5) | 9989 (51.3) |
| Female | 22 (52.5) | 9471 (48.7) |
| Missing | 0 | 0 |
| Ethnicity (n, %) | ||
| White | 29 (76.9) | 15 948 (87.3) |
| Mixed | <5 | 601 (3.2) |
| Indian | <5 | 500 (1.8) |
| Pakistani or Bangladeshi | 9 (12.1) | 1348 (3.9) |
| Black or black British | <5 | 740 (2.7) |
| Other | 0 | 305 (1.2) |
| Missing | 0 | 18 |
| NIC admission (n, %) | ||
| No neonatal/perinatal illness | 13 (27.2) | 10 229 (52.5) |
| Neonatal/perinatal illness without NIC admission | 16 (45.5) | 6764 (38.0) |
| Neonatal/perinatal illness with NIC admission | 12 (27.3) | 1773 (9.5) |
| Missing | 3 | 694 |
| Maternal prenatal smoking (n, %) | ||
| Non-smoking | 28 (73.9) | 12 017 (65.9) |
| Smoking | 13 (26.1) | 6687 (34.1) |
| Missing | 3 | 756 |
| Highest maternal education level by end of follow-up (n, %) | ||
| NVQ level 1, equivalent to leaving school <16 years | <5 | 1395 (7.0) |
| NVQ level 2, equivalent to age 16 leaving school | 11 (28.4) | 4968 (26.0) |
| NVQ level 3, equivalent to age 18 leaving school | <5 | 2808 (14.6) |
| NVQ level 4, equivalent to university education | 10 (27.4) | 5498 (31.8) |
| NVQ level 5 (highest), equivalent to university education including postgraduate qualifications | 5 (15.9) | 1448 (8.2) |
| Other | 12 (19.4) | 3225 (12.4) |
| Missing | 0 | 118 |
| Mean maternal age at cohort child’s birth, years (95% CI)* | 26.5 (24.9 to 28.1) | 28.9 (28.7 to 29.1) |
| Missing | 0 | 96 |
Percentages are adjusted for sample design.
*Geometric mean after natural log transformation.
NIC, neonatal care unit including neonatal intensive care and special care baby unit; NVQ, national vocational qualifications; PCHI, permanent childhood hearing impairment.