A sporadic case of delayed implantation after in-vitro fertilization in the human?

A possible case of delayed implantation after in-vitro fertilization (IVF) is described, The patient was sterilized in 1981, and made fertile again by tubal anastomosis in 1988, In 1990 and 1992 the patient had two right-sided tubal pregnancies, the first was treated with prostaglandin instillation, the second with salpingectomy. In connection with the salpingectomy in 1992, the left tube was observed to be constricted in the middle part and with phimosis of the ostium. In 1994 three IVF embryos were transferred, but 15 days after the transfer, serum human chorionic gonadotrophin (HCG) was negative (<10 IU/ml). Seven weeks after the embryo transfer, menstruation was still missing, and the serum HCG was now positive (329 IU/ml). Subsequent ultrasound scans were compatible with an intrauterine pregnancy, progressing normally, but 5 weeks delayed compared with the oocyte aspiration. The pregnancy was successfully carried to term. Such a long delay in detection of HCG, in association with a normal pregnancy, has not been described in the literature before.