Ultrasonographic criteria for non-viability of first trimester intra-uterine pregnancy.

This prospective cohort study evaluated the performance of transvaginal sonography in the assessment of first trimester intra-uterine pregnancy. Consecutive women with singleton pregnancies who underwent a first trimester transvaginal sonographic examination between May 1995 and March 1996 were included. Women had to have an intra-uterine gestational sac and time since last menstrual period of less than 12 weeks. In case of absent cardiac activity and a crow-rump length < 12 mm, the test sonography was repeated with a 7 to 10 days interval. A final diagnosis, that was considered to be the gold standard in further analysis, was established by sonography performed one week after the last test sonography. Among 372 pregnancies, there were 92 (25%) non-viable. The combination of absence of cardiac activity and absence of a yolk sac appeared to be a highly specific criterion whenever the mean sac diameter was > or = 16 mm or whenever a crown rump length was > 5 mm. We conclude that single transvaginal sonography is a reliable test to diagnose non-viable pregnancy in case the MSD is > or = 16 mm or in case the crown rump length is > 5 mm. The combination of absence of cardiac activity and absence of a yolk sac virtually rules out the possibility of a viable pregnancy in these patients.