Miscarriage diagnosis and gestational age estimation in the early first trimester of pregnancy: transvaginal versus transabdominal sonography

A comparison is made between 290 patients examined using transabdominal sonography and 308 patients examined using transvaginal sonography. Patients with suboptimal menstrual histories and threatened miscarriages were excluded from these two groups of patients. The transabdominal and transvaginal sonography examinations were carried out while the patient's bladder was empty, so that there was no delay between the clinical and sonographic examinations. In this way there was no patient discomfort from a full bladder. In normal pregnancies after 42 days of amenorrhea, the percentage visualization rates of the chorionic sac, of the embryo with heart activity and of the yolk sac were measured. There were no significant differences between the two groups. The two techniques were able to provide a reliable diagnosis of miscarriage on embryos >or= 4 mm or with chorionic sacs >or= 10 mm mean diameter. However, before 42 days of gestation, transvaginal sonography was better than transabdominal sonography at diagnosing miscarriage. The percentage of anembryonic pregnancies was higher in the transabdominal sonography group (21%) than in the transvaginal sonography group (7%), despite similar gestational ages at the time of a positive diagnosis. Thus, a transabdominal scan can be used after 42 days and borderline cases can be referred for transvaginal sonography for confirmation.