Persistent trophoblast after conservative treatment of tubal pregnancy: prediction and detection. The incidence of persistent trophoblast and risk of second surgical intervention after conservative treatment of tubal pregnancy are substantial. The preoperative and postoperative hCG patterns in patients with tubal pregnancy were studied to see whether this information could predict and detect persistent trophoblast at an early stage. Ninety-eight women with tubal pregnancy underwent conservative surgical treatment by laparoscopy or laparotomy. Eight developed postoperative complications necessitating a second operation, and seven of them had both biochemical and histologic evidence of persistent trophoblastic activity. In seven of 31 patients with preoperative hCG above 3000 IU/L, a second operation was necessary, whereas in 67 with preoperative hCG levels below 3000 IU/L, only one such intervention was necessary. Eight of the 22 patients with hCG above 1000 IU/L on the second day after surgery and seven of 11 patients with hCG above 1000 IU/L on the seventh day after surgery later needed a second surgical procedure. In contrast, 86 of 87 women with hCG below 1000 IU/L on the seventh day after surgery had an uneventful convalescence. We conclude that pre- and postoperative hCG measurements can identify patients at risk of developing persistent trophoblast. Further, in patients with preoperative hCG titers below 3000 IU/L, we recommend conservative surgery followed by measurement of hCG 1 week postoperatively. 