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Characteristics of Participants in Study One
| Demographic Variable | Frequencies |
|---|---|
| N (%) | |
| Sex | |
| Male | 7601 (51·08) |
| Female | 7280 (48·92) |
| Social economic status | |
| Manual | 2808 (18·87) |
| Non-manual | 9398 (63·15) |
| Missing | 2676 (17·98) |
| Ethnicity | |
| Non-white | 609 (4·09) |
| White | 11,468 (77·06) |
| Missing | 2805 (18·85) |
| Mother Parity | |
| Primipari | 5770 (38·77) |
| Multipari | 7154 (48·07) |
| Missing | 1958 (13·16) |
