Lifetime patterns of contraception and their relationship to unintended pregnancies

Abstract

Background: For the past 30 years many effective methods of contraception have been available, yet unintended pregnancy rates still range from 30% to 50% in many populations. We examined patterns of women's contraceptive use throughout their lives and relate them to unintended pregnancy.

Methods: A total of 396 women aged 18 to 50 years chosen by convenience sampling from a family practice residency office were interviewed in a cross-sectional study about their history of using and changing contraception, and whether they believed they became pregnant while using a method of contraception. We analyzed the data for correlations and significance using chi-square and Student t tests.

Results: Most women had used both condoms and oral contraceptive pills, and tried an average of 3.54 methods during a lifetime. Two patterns of women's use of contraception emerged that describe 75% of the women. One third of the women--those who indicated a pattern of following their first method with a less effective method--are significantly more likely to have an unintended pregnancy while using contraception (odds ratio=1.4). The other group (50% of the entire sample) used increasingly effective methods and were less likely to have an unintended pregnancy.

Conclusions: Pregnancy is an inherent natural consequence of sexual intercourse, even when using very effective contraceptive methods. By asking a few questions about a woman's history of contraceptive use, physicians may be able to determine those who are more likely to be at risk for an unintended pregnancy.