Patients undergoing assisted reproduction are advised to abstain from intercourse to prevent the possibility of multiple pregnancy. If patients do not follow this advice, multiple dizygotic pregnancy or even a heterotopic pregnancy can result. We report the case of a 28-year-old nulliparous female with unexplained infertility who underwent freeze-all vaginal oocyte retrieval. Twenty-one days later she presented with vaginal bleeding (similar to menstruation) and right lower-quadrant pain. The results of ultrasound scanning and a laboratory work-up were consistent with an ectopic pregnancy. She underwent laparoscopic right salpingectomy for a tubal ectopic pregnancy. We recommend sexual abstinence during assisted reproduction to lower the risk of multiple pregnancy and especially of heterotopic pregnancy. Keywords: In vitro fertilization, Ectopic pregnancy, Superfecundation, Superfetation