Assessment of the implantation site by transvaginal ultrasonography

Abstract

To investigate the implantation site in a singleton pregnancy. Transvaginal ultrasonography (US) was performed at the mid or late follicular phase and/or at very early gestation before 6 weeks. Ultrasound monitoring was performed on 21 women with spontaneous cycles or treated by administration of 2.5 mg/d bromocriptine mesylate (Parlodel; Sando Co., Tokyo, Japan) for occulted hyperprolactinemia at the Fertility Clinic of the Department of Obstetrics and Gynecology at Gunma University Hospital. The site of the ovary with a growing follicle and/or a corpus luteum of pregnancy, and the location of a gestational sac in longitudinal and transverse views were observed. When ovulation occurred in the right ovary, 12 of the 14 gestational sacs were located on the right wall, 1 on the midwall, and 1 on the left wall. Ovulation in the left ovary resulted in 5 gestational sacs located in the left wall and 2 on the midwall. That is, of 21 gestational sacs, 17 were located on the ipsilateral uterine wall to the ovulating ovary, 3 on the midwall, and only 1 on the contralateral. Implantation occurs on the ipsilateral uterine wall to the ovulating ovary.