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ArticleTitle	Determination of Blastocyst Implantation Site in Spontaneous Pregnancies Using Three-Dimensional Transvaginal Ultrasound
AuthorList	Shinji Minami, Kaisuke Ishihara and Tsutomu Araki
Affiliation	Department of Obstetrics and Gynecology, Nippon Medical School
Language	EN
Volume	70
Issue	3
Year	2003
Page	250-254
Received	November 22, 2002
Accepted	December 9, 2002
Keywords	implantation site, three-dimensional transvaginal ultrasound, early gestational sac (E-GS), blastocyst
Abstract	Three-dimensional transvaginal ultrasound was used to determine the location of early gestational sacs (E-GSs) and, as a result, the physiological implantation sites of human blastocysts. We examined 138 patients who were found by three-dimensional transvaginal ultrasound to have a GS with an inner diameter of 3 to 6 mm (E-GS). The uterine cavity was divided into three parts: upper, middle, and lower regions. The upper region was subdivided into the right, middle, and left areas, and the middle region was subdivided into the right and left areas. Thus, overall 6 areas were designed and the frequency of the E-GS detection in each area was evaluated. Of the 138 patients, 123 (89.1%) had E-GSs detected in the upper region, which was found to be the most frequent region. When the frequency of E-GS detection among the upper three areas was compared, the right and left upper areas had a higher frequency than the middle upper area. As to the miscarriage rate, patients with E-GSs detected in the upper region had a significantly lower rate than those in the middle and lower regions (p<0.05). The endometrium suitable for human blastocyst implantation under physiological conditions is at the uterine fundus, especially near the uterotubal junction.
Correspondence to	Shinji Minami, MD, Department of Obstetrics and Gynecology, Nippon Medical School Second Hospital, 1-396 Kosugi-cho, Nakahara-ku Kawasaki, Kanagawa 211-8533, Japan Shinm@nms.ac.jp