Abstract
OBJECTIVE: Our objective was to measure the sensitivity and specificity of a six-item "pregnancy checklist" at excluding early- or luteal-phase pregnancy among women with a negative urine pregnancy test who were initiating contraception. STUDY DESIGN: This was a secondary analysis of the Contraceptive CHOICE Project, a prospective cohort study of 9256 women in the St. Louis region. Women who had a negative urine pregnancy test on the day of enrollment were included in this analysis. Women with a positive urine pregnancy test or without urine pregnancy testing were excluded. We identified all luteal-phase pregnancies that occurred among women with a negative urine pregnancy test. We calculated the sensitivity, specificity, positive predictive value and negative predictive value (NPV) and likelihood ratios of the pregnancy checklist for excluding luteal-phase pregnancies. RESULTS: There were 6929 women included in this analysis; 69% of these women met at least one checklist criterion to exclude pregnancy ("negative screen"). There were 36 luteal-phase pregnancies (0.5%) subsequently diagnosed among women with a negative urine pregnancy test. The sensitivity and specificity of the checklist were 77.7% and 69.1%, respectively. The NPV of the checklist was 99.8% and the positive predictive value was 1.3%. CONCLUSION: Among women with a negative urine pregnancy test, the pregnancy checklist can be used to safely exclude more than 99% of early pregnancies at the time of contraceptive initiation. IMPLICATIONS: In patients with a negative urine pregnancy test, a pregnancy checklist using six criteria based on patient history has high NPV in excluding early pregnancy. This checklist can be used to facilitate same-day initiation of contraceptive methods, including long-acting reversible contraception. Although the checklist had a high false positive rate, initiation of contraception should not be delayed in women with a "positive screen." Rather women who desire an intrauterine device or implant can be "bridged" with a shorter-acting method until pregnancy can be excluded.