Second trimester pregnancy in a rudimentary uterine horn

Abstract

Sir, We wish to call attention to the case of a 34-year-old woman who presented to the emergency clinic with severe abdominal pain. She believed herself to be 13 weeks pregnant. The pregnancy had so far been uneventful. She had not attended the antenatal care program and had undergone no ultrasound examinations during her pregnancy. Earlier on the same day her general practitioner had reported ‘size of uterus according to gestation’. She had previously given birth to three children, the first child by cesarean section in week 29 and the second and third child by term vaginal delivery. On examination she was awake and conscious, but pale and in severe pain. Blood pressure was 98/65 mmHg and pulse 73 bpm. The hemoglobin was 6.0 g/l and serum-hCG 22,252 iu/l. There were signs of peritoneal irritation in the left iliac fossa. Transvaginal ultrasound revealed an empty uterus and a small hyperechoic mass close by the left ovary. The right ovary appeared normal and no significant free fluid was found in the Pouch of Douglas. An ectopic pregnancy was suspected. An emergency laparotomy was performed revealing massive hemoperitoneum. A ruptured rudimentary horn containing the placenta was found on the left side of the uterus. The fetus was found floating in the abdominal cavity. It was estimated to be of 16 weeks of gestation according to crown-heel length. There were no visible malformations. An excision of the ruptured uterine horn along with the placenta and a left salpingectomy was performed. Measured blood loss was 4.8 l and blood transfusions and fresh frozen plasma were given. The woman recovered without complications and was discharged 4 days later. This case illustrates an extremely rare and potentially life-threatening condition that remains a diagnostic challenge. It is to the best of our knowledge the first reported case of a ruptured uterine horn pregnancy following two term vaginal deliveries and a cesarean section. Congenital uterine malformations occur in 1:200 to 1:600 women (1). The presence of a rudimentary uterine horn is a result of abnormal development of one of the Müllerian ducts. In a review of 568 cases of rudimentary uterine horn pregnancies a rupture rate of 50.1% was found with 80% occurring before the third trimester (2). The maternal mortality rate fell from 23% in the 1920s to less than 0.5% more recently. This woman had not previously been diagnosed with a uterine malformation. In the operation notes of the cesarean section ‘a fibroma-like structure at the origin of the left salpinx’ was described, which is likely to have been the rudimentary horn. Women with uterine malformations have a higher risk of obstetric complications, including preterm labor (3). Prior knowledge of this condition would thus be valuable, but the sensitivity of ultrasound for diagnosing rudimentary horn pregnancies is only 29% (4). There are a few reports of rudimentary horn pregnancies proceeding to term, but immediate surgery is the standard treatment when the diagnosis is made.