Heterotopic pregnancy is an extremely rare condition in which an intrauterine and an extrauterine pregnancy co-exist. In spontaneous conceptions, heterotopic pregnancy is rare, occurring in an estimated 1 in 30,000 spontaneous pregnancies (Tad et al., 1996), and is thought to occur as a result of multiple ovulation or transfer events [14], facilitated by simple ovulation induction, insemination or IVF/ICSI techniques. The majority of these pregnancies (around 80 %) end in the first trimester [8]. Ultrasound is the best diagnostic imaging test (Tad et al., 1996) but magnetic resonance imaging (MRI) could be useful in cases where location of the site of pregnancy or placental implantation is difficult [1]. The treatment of heterotopic pregnancy must be as minimally invasive as possible to preserve the development of the intrauterine pregnancy. The reference treatment is surgical, either by laparotomy or laparoscopy, depending on the time of diagnosis [7]. Nonsurgical management of early ectopic pregnancy has also been described in some case reports and typically involves in situ methotrexate or potassium chloride injection [13].

In most series and case reports, the heterotopic pregnancies show no differences in gestational age. Superfetation, defined as the coexistence of 2 or more foetuses of different gestational ages, remains exceptional and poorly explained. Here, we present a case of a spontaneous heterotopic pregnancy with superfetation consisting of an intrauterine pregnancy of 5 + 4 WG coexisting with an abdominal pregnancy in the pouch of Douglas of 8 + 1 WG.