Purpose: To test the reliability of established ultrasound (US) parameters in predicting the outcome of first-trimester pregnancy.
Materials and methods: The authors retrospectively reviewed 2,655 first-trimester US scans in 2,285 patients. Parameters tested against outcome were (a) a yolk sac and mean gestational sac diameter of 8 mm on transvaginal US scans, (b) an embryo and mean sac diameter of 16 mm on transvaginal US scans, and (c) a difference between the mean sac diameter and crown-rump length of less than 5 mm (oligohydramnios) at 5.5-9.0 weeks gestation.
Results: Thirty (22%) of 135 patients without yolk sacs and with an 8-mm mean sac diameter developed live embryos: 24 had normal follow-up or delivery; six were lost to follow-up. Five (8%) of 59 patients with no depiction of embryos and with a 16-mm mean sac diameter developed live embryos: Two delivered, one spontaneously aborted, one had death of one twin embryo before being lost to follow-up, and one was lost to follow-up. Seventeen (0.74%) of 2,285 patients had early oligohydramnios: Six (35%) had normal follow-up scans or delivery, two (12%) spontaneously aborted, and nine (53%) were lost to follow-up.
Conclusion: Established parameters predictive of early pregnancy failure potentially result in misdiagnosis of nonviability or poor prognosis when applied to a large, unselected patient population. Close follow-up is necessary in cases with borderline abnormal findings.