Rudimentary horn pregnancy, a rare and unusual type of ectopic pregnancy, occurs in women who have a uterine malformation known as unicornuate uterus with rudimentary horn. 

Rudimentary horn pregnancy, a rare and unusual type of ectopic pregnancy, occurs in women who have a uterine malformation known as unicornuate uterus with rudimentary horn. This situation carries a significant risk of severe complications such as uterine rupture and internal bleeding, which makes its identification and management particularly complex.

Anatomy and Pathophysiology

the prevalence of congenital uterine malformations in the female population is estimated at 3-4%. They result from a defect or arrest of development of the Mullerian ducts during embryogenesis. There are several types of malformations, depending on the stage of embryogenesis reached (migration, fusion or septal resorption). When one of the two Müllerian ducts only partially develops, the result is a unicornuate uterus with a more or less developed rudimentary horn (non-communicating in 83% of cases). The latter can be solid or contain a cavity covered with endometrium which in this case can be rare, or even exceptional, the site of an ectopic pregnancy by trans-peritoneal migration of sperm or fertilized egg.

Risk Factors and Epidemiology

The incidence of these pregnancies is thus estimated between 1 in 76,000 and 150,000 pregnancies with a high risk (close to 80%) of uterine rupture of the rudimentary horn (probably due to a reduction in the muscular portion) and therefore of massive hemoperitoneum. 

This risk is particularly important during the 2nd trimester of pregnancy

Diagnosis

While ultrasound is generally a first-line examination in early pregnancy, it has a low sensitivity (26-33%) for the diagnosis of uterine malformation, including outside of pregnancy. 

MRI remains the reference examination for genital malformations and their classification according to the ESHRE/ESGE consensus

Complications and Evolution

Uterine rupture occurs in 80% of cases before 20 weeks, leading to a life-threatening emergency. Rigorous monitoring helps prevent these complications through rapid treatment.

Internal bleeding, hemorrhagic shock Secondary infertility

Clinical Case

A 42-year-old woman was referred to our gynecology-obstetrics department for suspected ectopic pregnancy on the left rudimentary uterine horn. 

Without any particular pathological history 

She had no known family history, including no history of genito-urinary malformation. Her menstrual cycles were regular and not painful. The malformation was previously unknown (in particular, it had not been diagnosed during her first pregnancies) and the patient was completely asymptomatic.

Exploration of the abdominopelvic cavity revealed a ruptured rudimentary uterine horn measuring 12 cm and a left unicornuate uterus of normal size.

We estimate a complete left cornual rupture 

There was no communication between the uterus and the rudimentary horn. The tubes were thin and sinuous and the ovaries were normal.

Resection of the uterine horn was necessary to prevent the risk of recurrence

Prognosis and Recommendations

Patients with a unicornuate uterus should be monitored from the start of their pregnancy to detect abnormal implantation and avoid serious complications.

Early diagnosis is valuable and allows rapid adoption of a therapeutic strategy to avoid or at least limit the risk of uterine rupture with massive hemoperitoneum.

Pregnancy with a rudimentary horn is an obstetric emergency when it is complicated. Prevention is based on early diagnosis and appropriate surgical intervention