A unicornuate uterus with a rudimentary horn is a uterine anomaly resulting from the incomplete development of one of the Müllerian ducts and an incomplete fusion with the contralateral side. Pregnancy in a rudimentary horn of the uterus is a rare clinical condition that can lead to a catastrophic outcome when it ruptures with a reported incidence of 1 in 100,000 to 140,000 pregnancies. Usually the diagnosis is missed and may present as an emergency with haemoperitoneum. The majority of cases are diagnosed late, after the rupture has occurred [1,2].

The use of ultrasonography helps clinicians to diagnose uterine malformations earlier, which can then be confirmed by a Magnetic Resonance Image (MRI) or a laparoscopy. The standard treatment for a rudimentary horn pregnancy is surgical excision to prevent complications and recurrence [2,3].

A 26 -year-old PGR was referred to Dr RPGMC Tanda as a case of 19 weeks with diagnosis of intrauterine fetal demise which had been detected on a routine antenatal ultrasound. There was no history of abdominal pain or vaginal blood loss at any time. She had regular menstrual cycles associated with dysmenorrhoea. There was no significant past medical or surgical history. Her vitals were normal. A transabdominal ultrasound showed a single, non-viable, intrauterine fetus with fetal parameters corresponding to 19 weeks of gestation and decision was made to induce abortion after routine investigations. Oral Mifepristone 200 mg was given followed by misoprostol 400 microgram after 48 hours given vaginally every four hours for a maximum of five doses. The patient experienced uterine contractions, with minimal vaginal spotting but no cervical changes. Repeat TVS was done showing a normal cervix leading to a small empty uterus just above it and a non-viable pregnancy was seen above and on the right of the uterus. Pregnancy in a rudimentary horn of the uterus was suspected. An MRI of the pelvis confirmed the diagnosis of pregnancy in the rudimentary horn of the uterus. Exploratory laparotomy with excision of rudimentary horn along with ipsilateral fallopian tube was done. B/l ovaries, contralateral fallopian tubes, kidneys and other abdominal organs were normal. Post-operative period was uneventful (Figure 1,2).

Figure 1: Excision of Rudimentary Horn Along with Ipsilateral Fallopian Tube

Figure 2: MRI of the Pelvis

Intraoperative Findings

Uterus was unicornuate with pregnancy in rudimentary non communicating horn on right side. The myometrium of the rudimentary horn was thin and membranous. Both ovaries and fallopian tubes were grossly normal. Rudimentary horn along the products of conception was resected. No communication with uterus was present. On cut section of the rudimentary horn a single fetus was found along with placenta.

Uterine anomalies result from the failure of complete fusion of the Müllerian ducts during embryogenesis. The incidence in the general population is estimated to be 4.3%. A unicornuate uterus with a rudimentary horn is the rarest anomaly and results from the failure of one of the Müllerian ducts to develop completely and an incomplete fusion with the contralateral side [2-4].

The most accepted explanation is the trans peritoneal migration of the sperm cells or a fertilized ovum. These cases usually result in the rupture of the horn in the second or third trimester. 

The rupture occurs because of the underdevelopment of the myometrium and a dysfunctional endometrium. The key for diagnosis prior to the rupture is a high index of clinical suspicion. A history of severe dysmenorrhoea may be a clue for diagnosis [4,5].

A careful pelvic examination in the first trimester showing a deviated uterus with a palpable adnexal mass should provoke suspicion of a Müllerian anomaly. It can be confirmed by an ultrasound or MRI. On USG a variation in the thickness of the myometrium in two horns and a marked distance between them favour the diagnosis of a rudimentary horn pregnancy [1,3].

Approximately 38% of patients have coexisting renal abnormalities. Immediate surgery is recommended whenever a diagnosis of a pregnancy in the rudimentary horn is made. The traditional treatment is a laparotomy and the surgical removal of the pregnant horn to prevent rupture and recurrent rudimentary horn pregnancies [1,4].

Even with developments in ultrasound technology, untrained doctors still struggle to make the antenatal diagnosis of a pregnancy with a simple horn. Early intervention combined with a high index of clinical suspicion for uterine abnormalities can lower the mortality rate. The suggested surgical procedure for the best prognosis when a rudimentary horn pregnancy is detected is the removal of the horn with ipsilateral salpingectomy. The requirement for strong clinical suspicion of this uncommon illness is highlighted by this example.

1. Ambusaidi, Q. and C.Jha. “Pregnancy in the rudimentary uterine horn: case report of an unusual presentation.” Sultan Qaboos University Medical Journal, vol. 14, no. 1, February 2014, pp. e134–e138.

2. Saravelos, S.H. et al. “The pattern of pregnancy loss in women with congenital uterine anomalies and recurrent miscarriage.” Reproductive Biomedicine Online, vol. 20, no. 3, March 2010, pp. 416–422.

3. Buntugu, K. et al. “Rudimentary horn pregnancy: Prerupture diagnosis and management.” Ghana Medical Journal, vol. 42, 2008, pp. 92–94.

4. Jain, R. et al. “A rare case of intact rudimentary horn pregnancy presenting as hemoperitoneum.” Journal of Human Reproductive Sciences, vol. 3, 2010, pp. 113–115.

5. Okonta, P.I. et al. “Pregnancy in a noncommunicating rudimentary horn of a unicornuate uterus: A case report.” Cases Journal, vol. 2, 2009, article 6624.