Accuracy of a home based device for giving an early estimate of pregnancy duration compared with reference methods

A home pregnancy test with weeks since ovulation results had 93% agreement with time since ovulation and 99% with ultrasound, which provides an estimate more accurate than last menstrual period and earlier than ultrasound.

Sarah Johnson, Ph.D., Sonya Godbert, C.Stat., Paul Perry, Pauline Parsons, Louise Roberts, Philip Buchanan, John Larsen, M.D., Todd A. Alonzo, Ph.D., Michael Zinaman, M.D.

Volume 100, Issue 6, Pages 1635-1641.e1, December 2013


To assess a home pregnancy test’s accuracy to concurrently detect pregnancy and determine pregnancy duration.

Multicenter, prospective study.

Study sites in the United States.

Women actively attempting to conceive who have menstrual bleeds (18–45 years).

Volunteers collected early morning urine samples (three or fewer menstrual cycles). Pregnant volunteers underwent ultrasound dating scans. Ovulation day (LH surge +1 day) during pregnancy-resulting cycles was determined by quantitative measurement of LH. Random urine samples were tested with the hCG-measuring pregnancy test from 4 days before the expected period until 4 weeks later.

Main Outcome Measure(s):
A home pregnancy test’s accuracy in determining pregnancy duration compared with ultrasound and ovulation day.

Agreement between pregnancy test results and time since ovulation was 93% (confidence interval [CI], 91.5–94.4). Agreement with ultrasound was dependent on the formula: there was 99% agreement when calculated with adjustment for Hadlock formula bias (Pexsters; CI, 98.2–99.4) or using a nonbias formula (Wu; CI, 98.6–99.6), when ultrasound error was accommodated. Agreement was lower when bias/measurement errors were not accounted for (Wu, 86%, CI, 83.9–88; Hadlock, 80.8, CI, 78.2–83.3).

This home pregnancy test provides an accurate estimation of pregnancy duration in weeks categories, 1–2, 2–3, 3+ weeks since ovulation, thereby showing utility in dating pregnancy.

  • grassy2

    I am confused by this paper – it states that ultrasound was performed at weeks 11-13 after LMP but how can those ultrasound estimates of gestational age then be inside the windows 1-2,2-3 and 3+ weeks since ovulation (even if we add the 2 weeks follicular phase to those windows given 5 weeks or less since LMP)

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