Table 1

Characteristics of study population

MeasureNumber with dataPreterm (n=775)Term
(n=11 811)
P values
Prepregnancy factors
 Maternal age12 58627.5 (4.9)27.9 (5.0)0.0247
 Maternal socioeconomic group90520.930
  I—Professional22 (4.3%)460 (5.5%)
  Ii—Managerial158 (31.0%)2610 (31.0%)
  iiiN—Skilled non-manual41 (8.1%)685 (8.0%)
  iiiM—Skilled manual228 (44.8%)3729 (43.7%)
  iv—Semiskilled49 (9.6%)863 (10.1%)
  v—Unskilled11 (2.2%)196 (2.3%)
 Mother’s highest educational qualification*11 1750.005
  CSE170 (26.4%)2182 (20.7%)
  Vocational70 (10.9%)1079 (10.2%)
  O level205 (31.9%)3730 (35.4%)
  A level137 (21.3%)2291 (21.8%)
  Degree61 (9.5%)1250 (11.9%)
 Non-white ethnicity66 (9.3%)488 (4.5%)<0.001
Antenatal and intrapartum factors
 Primiparous11 632348 (48.7%)4804 (44.0%)0.227
 Maternal hypertension12 585105 (13.6%)406 (3.4%)<0.001
 Multiple birth12 586149 (19.2%)186 (1.6%)<0.001
Delivery11 465<0.001
 Spontaneous cephalic427 (58.3%)8191 (76.3%)
 Emergency caesarean section166 (22.7%)624 (5.8%)
 Elective caesarean section40 (5.5%)449 (4.2%)
 Instrumental62 (8.5%)1323 (12.3%)
 Breech37 (5.1%)146 (1.4%)
Infant and postpartum factors
 Male12 586443 (57.2%)6033 (51.1%)0.001
 Birth weight (g)12 4412347 (615)3456 (485)<0.001
 Birth length (cm)951847.0 (2.6)50.8 (2.3)<0.001
 Head circumference (cm)966432.4 (2.1)34.9 (1.4)<0.001
 Apgar at 1 min11 4679 (7–9)9 (8–9)<0.001
 Apgar at 5 min11 4679 (9–10)10 (9–10)<0.001
 Received resuscitation11 452182 (24.9%)838 (7.8%)<0.001
  • SD 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.