Fetal loss after implantation. A prospective study.

The incidence of post-implantation pregnancy loss in 197 women was determined prospectively. The diagnosis of pregnancy was based on the detection of human chorionic gonadotropin in the urine during the luteal phase of each menstrual cycle. There were 152 conceptions in the 623 cycles studied with a pregnancy loss rate of 43%. 14 of the pregnancies ended in clinically recognised spontaneous abortions and in 50 the sole evidence of pregnancy was an increased concentration of urinary hCG. The maximum conception rate achieved was 36% in the first cycle after removal of an intra uterine device.