Effect of prior pregnancy and combined oral contraceptives on baseline menstrual blood loss and bleeding response to intrauterine devices.

No effect of pregnancy was found on baseline menstrual blood loss (MBL) in women within one year of parturition or abortion. The increased bleeding response of women to intrauterine devices (IUDs) was found to be independent of pregnancy status during the year preceding IUD sertion. Women pregnant within a year of insertion had no different MBL than those pregnant more than a year prior to insertion. MBL quantified in subjects within three months of discontinuing combined oral contraceptives (OCs) was significantly lower than in prior non-OC users. Furthermore, MBL was significantly reduced in the former group during the first three menses following IUD insertion. At the sixth and twelfth menses post-insertion, MBL was still lower in prior OC users, but the difference between users and non-users was less and no longer statistically significant.