Table 3 Differences between sister controls and controls recruited through the general practitioner (GP controls)
|  | sister controls (n = 313) | GP controls (n = 430) | P value |
|---|---|---|---|
Age | 30 (18–58) | 34 (18–54) | <0.001 |
High education (n/N) (%) | 158/308 (51.3) | 293/428 (68.5) | <0.001 |
Is in committed relationship (n/N) (%) | 249/311 (80.1) | 341/428 (79.7) | NS |
Has had intercourse (n/N) (%) | 288/312 (92.3) | 407/426 (95.5) | NS |
Has offspring (n/N) (%) | 140/313 (44.7) | 201/429 (46.9) | NS |
Has previously consulted a gynaecologist for fertility problems (n/N) (%) | 29/301 (9.6) | 44/411 (10.7) | NS |