Table 1

Characteristics of women with full reproductive histories compared to those with incomplete reproductive histories as determined from five questionnaires

Women with incomplete data n=10262Women with complete data n=3451p Value
Categorical variables—n (%)
 Ethnicityn=8653n=3417
  White8381 (96.9)3370 (98.6)<0.001
 Social classn=7927n=3335
  I842 (10.6)664 (19.9)<0.001
  II3099 (39.1)1601 (48.0)
  III (non-manual)2135 (26.9)738 (22.1)
  III (manual)1261 (15.9)258 (7.7)
  IV and V590 (7.4)74 (2.2)
 Educationn=8739n=3425
  University level or above826 (9.5)742 (21.7)<0.001
 Single parent householdn=9136n=3403
  Yes616 (6.7)102 (3.0)<0.001
 Ever smokedn=9365n=3441
  Yes5124 (54.7)1369 (39.8)<0.001
Continuous variables—mean (SD*)
 Age at birth of the ALSPAC index childn=10258n=3451<0.001
27.4 (5.0)29.8 (4.4)
  • *T test for normally distributed data.

  • ALSPAC, Avon Longitudinal Study of Parents and Children.