A rare case of a heterotopic pregnancy after single embryo and blastocyst transfer is presented. A couple suffered from idiopathic infertility and underwent assisted reproduction techniques in a university hospital. Intercourse on the day of HCG administration was the probable cause for an in vivo fertilization of an oocyte that was not collected during the oocyte retrieval. The patient accessed a regional hospital with a massive haemoperitoneum in the 11th week of pregnancy with the confusing information that only one embryo had been transferred during the assisted reproduction treatment. After tubal pregnancy removal, the in-utero pregnancy proceeded normally but, at the time of the second trimester scan, a caudal regression syndrome was diagnosed and the patient decided to terminate the pregnancy.