LAUSR

BACKGROUND Mifepristone, used together with misoprostol, is approved by the US Food & Drug Administration for medication abortion through 10 weeks' gestation. While in-person ultrasound is frequently used to establish medication abortion eligibility, prior research demonstrates that people seeking abortion early in pregnancy can accurately self-assess gestational duration using date of their last menstrual period (LMP). In the present study, we establish the screening performance of a broader set of questions for self-assessment of gestational duration among a sample of people seeking abortion at a wide range of gestations. METHODS We surveyed patients seeking abortion at 7 facilities prior to ultrasound and compared self-assessment of gestational duration using 11 pregnancy dating questions to measurement on ultrasound. For individual pregnancy dating questions and combined questions, we established screening performance focusing on metrics of diagnostic accuracy, defined as the area under the receiver operating curve (AUC); sensitivity, or the proportion of people ineligible for medication abortion who correctly screen as such; and proportion false negative, defined as the proportion of the total sample who screen as eligible when they are not. We tested for differences across individual and combined questions in sensitivity, using McNemar's test, and in accuracy, using AUC and Sidak's adjusted p-values. RESULTS One-quarter (25%) of 1,089 participants were >70 days' gestation on ultrasound. Using date of LMP alone demonstrated 83.5% (95% CI: 78.4, 87.9) sensitivity at identifying people >70 days on ultrasound, with AUC of 0.82 (95% CI: 0.79, 0.85) and proportion false negative 4.0%. A composite measure of responses to number of weeks pregnant, date of LMP, and date got pregnant questions demonstrated 89.1% sensitivity (95% CI: 84.7%, 92.6%) and AUC of 0.86 (95% CI: 0.83, 0.88), with 2.7% false negative. A simpler question set focused on being >10 weeks or 2 months pregnant or having missed 2 or more periods had comparable sensitivity (90.7%, 95% CI: 86.6, 93.9) and proportion false negative (2.3%), but with slightly lower AUC (0.82, 95% CI: 0.79, 0.84). CONCLUSIONS In a sample representative of people seeking abortion nationally, broadening the screening questions used to assess gestational duration beyond date of LMP results in improved accuracy and sensitivity of self-assessment at the 70-day threshold for medication abortion. Ultrasound assessment for MA may not be necessary, especially when requiring ultrasound could increases COVID-19 risk or healthcare costs, restrict access, or limit patient choice.