Table 1. Characteristics of study population (n = 11,990).
| Measure | Number with data | Preterm (<37 weeks)(n = 722) | Term (37–42 weeks)(n = 11268) | P |
| Pre-pregnancy factors | ||||
| Maternal age | 11,990 | 27.5 (4.9) | 27.9 (4.9) | 0.0371 |
| Maternal socioeconomic group | 9,885 | 0.516 | ||
| I – Professional | 22 (4.0%) | 2,758 (29.5%) | ||
| Ii – Managerial | 163 (29.6%) | 3,692 (39.6%) | ||
| iiiN – Skilled non-manual | 223 (40.6%) | 1,124 (12.0%) | ||
| iiiM – Skilled manual | 76 (12.8%) | 1,038 (11.1%) | ||
| iv - Semi-skilled | 52 (9.5%) | 238 (2.6%) | ||
| v – Unskilled | 14 (2.6%) | 485 (5.2%) | ||
| Mother’s highest educational qualification* | 10,663 | 0.039 | ||
| CSE | 155 (25.8%) | 2102 (20.9%) | ||
| Vocational | 61 (10.1%) | 1044 (10.4%) | ||
| O Level | 201 (33.4%) | 3593 (35.7%) | ||
| A Level | 131 (21.8%) | 2181 (21.7%) | ||
| Degree | 54 (9.0%) | 1141 (11.3%) | ||
| Housing | 11179 | 0.346 | ||
| Mortgaged or owned | 479 (71.7%) | 7804 (74.3%) | ||
| Rented from municipality | 110 (16.5%) | 1564 (14.9%) | ||
| Private Rented | 79 (11.8%) | 1143 (10.9%) | ||
| Car ownership | 11184 | 583 (87.4%) | 9414 (89.5%) | 0.087 |
| Crowding index (no. people per room) | 11,023 | 0.476 | ||
| <0.5 | 279 (42.9%) | 4202 (40.5%) | ||
| 0.5–0.75 | 327 (50.2%) | 5455 (52.6%) | ||
| 0.75–1 | 29 (4.5%) | 511 (4.9%) | ||
| 1+ | 16 (2.5%) | 204 (2.0%) | ||
| Non-white ethnicity | 11828 | 60 (8.5%) | 562 (5.1%) | <0.001 |
| Antenatal and intrapartum factors | ||||
| Primiparous | 11105 | 350 (52.2%) | 5891 (56.5%) | 0.037 |
| Maternal Hypertension | 10,973 | 25 (3.7%) | 290 (2.8%) | 0.205 |
| Maternal Pyrexia | 10,973 | 6 (0.9%) | 57 (0.6%) | 0.279 |
| Multiple birth | 11,990 | 136 (18.8%) | 179 (1.6%) | <0.001 |
| Delivery | 10.972 | <0.001 | ||
| Spontaneous cephalic | 400 (58.5%) | 7851 (76.3%) | ||
| Emergency caesarean section | 155 (22.7%) | 597 (5.8%) | ||
| Elective caesarean section | 35 (5.1%) | 432 (4.2%) | ||
| Instrumental | 59 (8.6%) | 1266 (12.3%) | ||
| Breech | 35 (5.1%) | 142 (1.4%) | ||
| Infants and post-partum factors | ||||
| Male | 11,990 | 411 (56.9%) | 5757 (51.1%) | 0.002 |
| Birth Weight (g) | 111977 | 2356 (624) | 3455 (485) | <0.001 |
| Birth Length (cm) | 10.309 | 47.1 (2.7) | 50.9 (2.4) | <0.001 |
| Head Circumference (cm) | 10,953 | 32.4 (2.1) | 34.9 (1.4) | <0.001 |
| Apgar at 1 minute | 10,953 | 7.7 (1.9) | 8.4 (1.4) | <0.001 |
| Apgar at 5 minute | 10942 | 9.2 (1.1) | 9.5 (0.7) | <0.001 |
| Received resuscitation | 10,960 | 173 (25.4%) | 809 (7.9%) | <0.001 |
| Died before 8 years of age | 11,990 | 1 (0.14%) | 5 (0.04%) | 0.273 |
Standard deviations are given for means of normally distributed continuous variables and percentages for proportions.
*
CSE = Certificate in Secondary Education (commonly taken at 16 years of age); Vocational = City & Guilds (intermediate level), technical, shorthand or typing, or other qualification; O level = Ordinary level (commonly taken at 16 years of age); A level = Advanced level (commonly taken at 18 years of age), state enrolled nurse, state registered nurse, City & Guilds (final or full level) or teaching qualification; Degree = University degree.