Table 5.
Proposals for diagnostic criteria for miscarriage based on this study
| Our recommendations to definitively diagnose miscarriage | Positive predictive value (%, 95% CI) | Specificity (%, 95% CI) |
|---|---|---|
| Agreement with current criteria: | ||
| Presenting with no visible embryo or yolk sac, and mean gestational sac diameter ≥25 mm | 12/12 (100, 73.5 to 100) | 364/364 (100, 99.0 to 100) |
| Presenting with an embryo with no heart activity, and crown-rump length ≥7 mm | 17/17 (100, 80.5 to 100) | 110/110 (100, 96.7 to 100) |
| Suggested additional new criteria | ||
| Initial scan criteria: | ||
| Presenting with an embryo with crown-rump length ≥3 mm, and gestational age ≥70 days | 102/102 (100, 96.4 to 100) | 87/87 (100, 95.8 to 100) |
| Presenting with no visible embryo: mean gestational sac diameter ≥18 mm and gestational age ≥70 days (10 weeks) from date of known last menstrual period | 52/52 (100, 93.2 to 100) | 907/907 (100, 99.6 to 100) |
| Repeat scan criteria: | ||
| Presenting with no visible embryo (with or without visible yolk sac) with mean gestational sac diameter ≥12 mm and returning after at least seven days: no embryo with embryo heart activity visible | 130/130 (100, 97.2 to 100) | 150/150 (100, 97.6 to 100) |
| Presenting without an embryo (with or without visible yolk sac) with mean gestational sac diameter <12 mm and returning after at least 14 days: no embryo heart activity and mean gestational sac diameter has not doubled | 41/41 (100, 91.4 to 100) | 478/478 (100, 99.2 to 100) |
| Presenting with an embryo (irrespective of crown-rump length) without heart activity, and still no heart activity visible after at least seven days | 191/191 (100, 98.1 to 100) | 103/103 (100, 96.5 to 100) |
Modified Jeffreys method used for confidence intervals when percentages equalled 100% (or 0%). Standard Jeffreys methods used otherwise.