Attempts surgically to induce chorionic fusion between embryos

Intercornual fistulas were made in the uteri of 19 ewes in an attempt to induce chorionic fusion between fetuses. Ewes were 28 to 40 days pregnant with at least one fetus per horn. Sections were removed from the dorsomedial wall of each uterine horn, and left and right horns were sutured together around the openings to produce the fistulas. In some cases a doughnut-shaped sheet of silastic was inserted between the horns, and in most cases the chorioallantoic membranes of the respective fetuses were sutured to one another prior to suturing the uterine walls. In the 16 animals in which intercornual fistulas were constructed in the area of the intercornual ligament, no chorionic anastomosis was induced. In one of the three animals in which fistulas were produced distal to that ligament, the fistula remained patent 25 days post-surgery, and membranes of two female fetuses were joined, through the opening, by a narrow strand of chorionic tissue. We concluded that this technique was not a promising one for induction of choriovascular anastomosis.