Table 1

Distributions of birth weight, proportion of low birth weight births, age at childbirth and year of birth for subjects belonging to 67 795 mother-father-child trios (35 048 with sons and 32 747 with daughters) as registered in the Norwegian Medical Birth Registry 1967–98

Father Mother Son Daughter
Birth weight (g)
 Mean value3 5813 4293 5553 452
 Standard deviation531504580540
Per cent of births with low birth weight2.63.34.03.9
Age at childbirth (y)
 Mean value24.723.1
 Standard deviation3.03.1
Year of birth, number of subjects
 1967–6934 23718 509
 1970–7221 86425 095
 1973–759 11016 315
 1976–782 2946 663
 1979–812861 195
 1982–8441832
 1985–87369295
 1988–902 6662 517
 1991–937 3956 775
 1994–9613 67112 815
 1997–9810 94410 343