Unicornuate uterus is extremely rare. it presents 1/76,000 to 1/140,000 of pregnancies [2,7,10,11]. However, its occurrence is serious and may involve the vital maternal pc; its natural evolution is the almost inevitable rupture of the rudimentary hemiuterus in 80-90% occurring

frequently in the 2nd trimester [2,3,5,7,12,14]. This implies its early diagnosis at the very beginning of pregnancy allowing its early termination at the pre-rupture stage. However, the diagnosis of this type of ectopic pregnancy is laid in more than 50% at the rupture stage [12-14] nahum et al analyzed 588 cases of pregnancies on rudimentary horn having been reported in the literature between 1900 and 1999, the diagnosis was made at the rupture stage in 50%; having occurred in 80% before the 3rd trimester [10]. Seema et al reported 10 cases of uterine rupture in a retrospective analysis of 12 pregnancies on rudimentary horn [19]. 3 cases of uterine rupture in the 2nd trimester (20wk, 17wk, 24wk) were reported by Sujata et al in their retrospective analysis of 5 cases of rudimentary horn pregnancy admitted to their hospital between 2001 and 2010 [22].

This diagnostic delay can be justified by the fact that this rare ectopic pregnancy occurs in women whose uterine congenital malformation is not yet known and who have a history of normal pregnancies [2,12,13,16]. On ultrasound the pregnancy in a rudimentary horn can simulate a pregnancy of normal intrauterine

location due to the non-visualization of the normal hemiuterus latero-deviated by the gravid horn or take the appearance of a pregnancy in a bicornuate uterus.

pregnancy in a rudimentary horn can also be visualized on ultrasound as a latero-uterine pregnancy evoking a cornual, tubal or abdominal pregnancy, however, even if the diagnosis in this case is not established, it is indeed of an ectopic pregnancy systematically indicating a termination of pregnancy and therefore the therapeutic management is done at the pre-rupture stage. this is the case of our patient whose pregnancy was diagnosed as ectopic on ultrasound without suggesting a rudimentary horn pregnancy.

The sensitivity of ultrasound in the diagnosis of pregnancy on rudimentary horn of a unicornuate uterus is only 30% [8,12,16,17].

Tsafir proposes 3 sonographic criteria of strong suspicion of this type of ectopic pregnancy (19): a) pseudo asymmetric aspect of bicornuate pregnancy b) gestational sac surrounded by a layer of myometrium c) non-continuity of the gravid cavity with the cervical canal. The analysis of the ultrasound aspect of the pregnancy in our case shows the presence of a layer of musculature.

Magnetic resonance imaging, considered the gold standard in the diagnosis of uterine malformations, confirms the diagnosis [8,17,19]. Systematic termination of pregnancy is indicated in this type of ectopic pregnancy to prevent rupture of the rudimentary hemiuterus [8,9,12] even if sporadic cases of pregnancy carried to term are described in the literature [6,10]. management therapy consists of resection of the rudimentary horn with the homolateral fallopian tube.