Comparative study and evaluation of side effects of low-dose contraceptive pills administered by the oral and vaginal route . Ziaei S, Rajaei L, Faghihzadeh S, et al. Contraception 2002; 65: 329-331

This retrospective study looked at the bone mass density of women using combined oral contraception (n = 59), depot-medroxyprogesterone acetate (DMPA) (n = 34) or controls (n = 62) who had not used steroid contraception for 6 months. The groups were matched for body mass index, age, smoking, alcohol consumption, caffeine consumption and exercise. There was no matching for family history nor was this considered in the exclusion criteria. There was no consideration of the menstrual history of the controls or the DMPA users so there is no record as to whether the DMPA users were amenorrhoeic. The results are given on one measurement of bone density and not on serial readings. The criterion used for long-term use was 2 years, which does not match with any corresponding retrospective studies. Other papers considered in their discussion gave information from 1 to 5 years. There appears to be no consensus as to what constitutes long-term use. The conclusions of the study showed that bone loss in the DMPA group was only significant for the lumbar spine and no other site. There was no significant affect associated with combined oral contraception. The authors feel that their study will help to diminish concerns that hormonal contraception has a detrimental affect on bone density but they also recognise that only a prospective study can give a definitive answer. This paper is yet another that gives us a snapshot of women using DMPA and that the bone mass loss may not be as bad as maintained by some authorities, but the paper does not actually give a definitive answer.