Transcervical sonography: an investigational technique for visualization of the embryo

A catheter-based, miniature ultrasound transducer, operating at a frequency of 12.5 MHz, was introduced transcervically into the uterine cavity of 18 pregnant women about to undergo first-trimester abortion. Transcervical sonography showed the yolk sac and embryonic structures, such as brain vesicles, limb buds, liver, spinal canal, and umbilical cord with blood flow, in eight embryos at 5-8 menstrual weeks of age. As an investigational technique, catheter-assisted transcervical sonography offers a new diagnostic approach to imaging of the first-trimester human embryo.