| Methods |
'Case‐control study'. All Danish women < 60 years of age with histologically confirmed borderline ovarian tumours identified from the Danish Cancer Registry from 1989 to 1994 with histological diagnosis, who returned a completed questionnaire with exposure data (N = 263). Random sample of 3 controls per case were selected from the National Person Register, were matched by area of residence and age at time of cancer diagnosis, and completed a questionnaire. National study in Denmark from 1989 to 1994 |
| Participants |
N = 1721 women with at least 1 ovary. Mean age for cases 43.6 (range 22 to 59) years. Mean age for controls 46 (range 19 to 59) years |
| Interventions |
Fertility drugs, dosage, and number of cycles not reported |
| Outcomes |
Borderline ovarian cancer by histological diagnosis (see Table 2) |
| Notes |
Duration of exposure not reported |
| Risk of bias |
| Bias |
Authors' judgement |
Support for judgement |
| Selection bias |
High risk |
Live cases only and women who responded to questionnaire on exposure |
| Confounding |
Unclear risk |
Cases and controls were matched for age at time of diagnosis and area of residence. Factors adjusted for included parity, use of an oral contraceptive pill, menopause, use of hormonal replacement therapy, and smoking |
| Performance bias |
High risk |
Self‐reported (type of treatment ‐ oral/injection) with some checks with fertility clinics for confirmation. No blinding of assessors to case‐control status |
| Detection bias |
High risk |
Cancer registry; no blinding of assessors to exposure status |
| Attrition bias |
Unclear risk |
87.8% of questionnaires were returned, and all were selected for cases to analyse; 79.8% of questionnaires were returned for controls, and all were used for analysis |
| Selective reporting (reporting bias) |
Unclear risk |
Unclear if all investigated fertility drugs were reported |
