Earliest ultrasound finding of implantation?

Our purpose was to verify our earlier observation of an altered endometrial echo character during the periimplantation period, signifying the earliest detection of implantation by ultrasound.

The transvaginal ultrasound study used a 7.5-MHz probe on day 6 following preembryo transfer.

Of 31 embryo transfers studied. 8 (25.8%) were positive for this sign on day 6, whereas 9 patients later showed a gestational sac, giving an accuracy of this sign of 88.8% (8 of 9).

The normal secretory-phase endometrium shows a typical, evenly distributed hyperechogenecity described earlier by Hackeloer (1). In some cases of proliferative phases, too, this echo pattern has been reported by others (2, 3), and observed by us in stimulated and unstimulated cycles, and has been named type A endometrium by Gonen et al. (4) Both these varieties are seen to have an even, unbroken outline at the anterior and posterior myometrial-endometrial interphase. We report what we believe to be the earliest ultrasound picture of implantation, resembling this variety of endometrial echo but having an irregular outline (Fig. 2).