Table 1. Perinatal Characteristics of the Study Sample (N=791)
VariablesAll (N=791)Early Term (n=110)Full Term (n=533)Late Term (n=148)
Sex, % female52.054.551.452.0
Gestational age, wks39.7 (1.0)37.7 (0.4)39.7 (0.4)41.1 (0.3)
Socioeconomic position, % manual27.331.826.327.7
Birth weight, kg3.433 (0.478)3.233 (0.492)3.445 (0.473)3.532 (0.465)
Birth weight, Z scores0.02 (1.03)0.52 (1.12)0.03 (0.99)−0.38 (0.89)
Mode of delivery, %
Vaginal (normal)81.371.882.285.1
Vaginal (assisted instrumental)a14.220.013.113.5
Cesarean4.58.24.71.4
Breastfeeding, %
Never82.481.882.284.8
≤3 Mo11.112.710.711.5
>3 Mo6.55.57.14.7
Maternal age, y27.8 (5.6)27.6 (5.9)28.0 (5.6)27.1 (5.0)
Maternal BMI, kg/m224.6 (4.0)24.7 (4.3)24.5 (3.8)24.8 (4.1)
Normal weight, %65.062.765.965.5
Overweight, %26.529.125.528.4
Obese, %8.58.28.68.1
Maternal smoking habits, %
Non‐smoker63.567.363.859.5
Sporadic smoker3.83.63.26.1
Regular smoker32.729.133.034.5
  • Data are mean (SD) unless otherwise indicated. BMI indicates body mass index.

  • a Including forceps or vacuum (ventouse).