Risk score aids in identifying spermicide failure

1. Previous pregnancies, age <35 years and increasing proportion of sex acts without protection were predictive of incidental pregnancy.

2. A risk scoring tool demonstrated excellent negative predictive value for unintended pregnancy.

Evidence Rating Level: 1 (Excellent)      

Study Rundown: Unintended pregnancies comprise about half of all pregnancies in the United States. While long acting contraceptive methods (LARCs) have been demonstrated to be the most effective in preventing pregnancy, many women still opt for barrier and chemical methods due to cost, autonomy, and safer side effect profiles. Spermicides are a convenient contraceptive method but are associated with a high failure rate, exceeding 25% with typical use and between 10-20% with perfect use. Given this high risk for unintended pregnancy with spermicide use, experts suggested it may be useful for women to have a risk scoring tool to evaluate whether spermicides are likely to help them prevent pregnancy to permit more informed decision-making about their contraceptive choice. In the present work, the authors pooled data from three randomized controlled trials (RCTs) to identify characteristics of spermicide users that were predictive of contraceptive failure resulting in pregnancy.

Results demonstrated that increasing gravity, age <35 years, and increased percentage of unprotected sex acts were predictive of unintended pregnancy. Using this information, they developed a simple risk score tool to identify women at low risk for pregnancy while using spermicide. A major strength of this meta-analysis included rigor of studies included such that only randomized controlled trials were assessed. Weaknesses included post-hoc analysis and limited generalizability to non-black, non-white populations. Further evaluation of the created risk score tool in prospective studies to better characterize its role in patient-centered decision-making is warranted.

Click to read the study in AJOG

Relevant Reading: Estimating contraceptive efficacy: the case of spermicides

Study Author, Dr. Courtney A. Schreiber, MD, MPH, talks to 2 Minute Medicine: University of Pennsylvania, Program Director, Family Planning Fellowship, Associate Professor of Obstetrics and Gynecology

“While Long Acting Reversible Contraceptive (LARC) methods are the most effective methods for women across the board, they can be hard to access for many women. Our study shows that there are women for whom spermicides, which are available over the counter, can be highly effective. Convenience is important for women, and until we have more over-the-counter contraceptives available, decision tools can help women individualize the balance between accessibility and efficacy.”

In-Depth [meta-analysis]: This secondary analysis evaluated the relationship between spermicide user characteristics and unintended pregnancy among 621 women using 3 different spermicides, C31G (n = 138), BufferGel (n = 300) and FHI Spermicide (n = 183). The primary outcome of interest was unintended pregnancy.

Women who were over age 35 were less likely to have an unplanned pregnancy (OR 0.19, CI 0.06-0.58). At least one previous pregnancy was associated with increased likelihood of unintended pregnancy (OR 3.38, CI 1.43-7.99 for 1 previous pregnancy). Percentage of unprotected sex acts was associated with slightly increased odds of pregnancy (OR 1.03, CI 1.02-1.05). A scoring system evaluating these three factors had an area under curve of 0.73 (CI 0.669-0.793). Using a cut-point of 4 to classify women as high risk of spermicide failure, the scoring tool had a negative predictive value of 97%.

Image: PD

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