Table 1

Characteristics of the analytic sample categorised by potential confounder and mediator variable status

EthnicityBirth weight
 White89.65 Heavy11.13
 Mixed0.95 Normal82.02
 Indian1.85 Low birth weight6.86
 Pakistani2.74 Missing<0.01
 Bangladeshi0.72Gestational age
 Black Caribbean1.08 37 weeks or over91.86
 Black African1.19 Pre-37 weeks7.39
 Other (including Chinese)1.83 Missing0.75
Maternal educationGestational diabetes
 NVQ level 18.09 No98.85
 NVQ level 229.83 Yes1.15
 NVQ level 314.42Delivery
 NVQ level 429.9 Vaginal68.28
 NVQ level 53.65 Forceps3.93
 Overseas qualifications2.22 Vacuum5.86
 None of these11.79 Other0.72
 Missing<0.01 Planned caesarean9.26
Mother’s age band Emergency caesarean11.96
 14–2423.65Labour complications
 25–3459.07 Yes33.53
 35–5117.28 No66.47
Siblings in house
 Three or more6.55
Step-siblings in house
 At least one9.17
Smoked during pregnancy
 Did not smoke71.62
 Gave up in first month7.00
 Smoked after first month21.38
Alcohol during pregnancy
 Less than once per month15.03
 1–2 times per month7.86
 1–2 times per week8.05
 3–7 times per week2.01
  • Percentages relate to weighted number of cases (n=17 113). All estimates obtained using ‘svy’ commands in Stata.