In previous studies, a physician’s involvement did not affect a woman’s use or satisfaction with contraception.11 In our study most women had discussed their satisfaction with contraceptive methods with a physician. Discussion or lack of discussion did not affect methods chosen, number of methods chosen, or the chance of becoming pregnant while using birth control.
Other studies have suggested that women may choose highly effective contraception, especially irreversible contraception, because of fear of pregnancy, then have a more satisfying sexual life because this fear has been reduced.12,13 However, in our study population, no form of contraception significantly affected a woman’s satisfaction with her sexual life.
There was a very low effectiveness rate in our population of women who used DMP. DMP is usually a very effective method that boasts ideal and actual failure rates of less than 3 in 1000 women-years (99.7%). However, 11 of the 82 women in our study reported that they became pregnant while using DMP, for an effectiveness rate of only 86%. The average duration of use of DMP in these women was only 11 months (range=1 week to 60 months). It cannot be determined from the data, but because the average length of use is so short many of these pregnancies may have occurred in women who received only 1 shot and never returned. They considered themselves users of DMP, even though the medication’s effectiveness had waned. Women may have also wanted to please the interviewer or give an answer they thought was appropriate. This may be a major bias of our method of obtaining data. It is perhaps more socially acceptable to claim to be using DMP than to admit to using no method at all, or to claim to be using condoms consistently when actually only using them occasionally.
Limitations
Our study has inherent difficulties. It was a convenience sample; women who were interviewed might have been visiting the physician to obtain a prescription method of contraception, while those who used over-the-counter or rhythm methods may not have been counted proportionally. There is also an inherent recall bias. Women may be more likely to remember a significant fact (such as a pregnancy) as the reason for changing a birth control method rather than the headaches or irregular bleeding that may have contributed to the change. The women may have been more likely to tell the interviewer they were using a birth control method that failed than to say they stopped or forgot to use their method. This would make the methods look less effective.
However, reasons for changing or using contraception are based on the women’s perceptions, so although recall bias may occur, the women’s perceptions are as important as the actual happenings. Whether a woman became pregnant while using a particular method was defined by her recall of the situation. No objective measurements (counting pills, checking charts for DMP shots) were performed. The woman’s perceptions were important for our study because they affected her subsequent use of contraceptive methods. This induced a bias, however, from the interpretation by the women. Another flaw of our study is that it was difficult to determine when a woman was using more than one method concurrently; this would give a higher effectiveness rate than either method individually and overall.
A prospective concurrent study of women’s use of contraception over time would give better answers about why women change contraception and how they use it.
Conclusions
Pregnancy must be considered a possible risk even for those women using an effective method of contraception over a lifetime. OCPs had a lifetime risk of one third for pregnancy in our study population. However, by determining a woman’s pattern of contraceptive use, the health care professional may be able to pinpoint some women who are at higher risk for unintended pregnancies. These women should be followed up more closely and urged to use more effective contraception.