Unruptured pregnancy in a non‐communicating heterotopic right fallopian tube associated with left unicornuate uterus: evidence for transperitoneal sperm and oocyte migration

We report on the case of a 29-year-old patient with an unruptured pregnancy in a non-communicating heterotopic right fallopian tube. This tube was associated with a unicornuate uterus (Buttram class IIB) with a normal contralateral tube and ovary and agenesis of the right kidney. The corpus luteum of pregnancy was in the left ovary. This case provides supportive evidence for the phenomenon of transperitoneal sperm and oocyte migration. A 29-year-old second gravid woman presented at 12 weeks' menstrual age with a mild and painless vaginal bleeding. The patient's medical history was uneventful with a normal delivery at 40 weeks gestation. On physical examination, the abdomen was soft and a small amount of bright red blood in the vaginal vault was seen. Bimanual examination revealed no palpable adnexal masses. The ultrasound examination revealed an empty uterus. The serum titre of the β-subunit of human chorionic gonadotropin, determined four times in 2-day intervals, showed a pathologic trend with serum levels of 4000 mIU/ml. Laparoscopy was performed and revealed a left unicornuate uterus with a normal fallopian tube and ovary on the left side. A heterotopic right fallopian tube was found attached to the peritoneum beside the right colonic flexure. This fallopian tube was 3–4 cm in length and consisted of an ampulla and a well-developed fimbriated end. It contained an extra-uterine gravidity (EUG) (Fig. 1). The unicornuate uterus was characterized by a slender, fusiform solitary horn that appeared laterally deviated with a single fallopian tube originating from the canal apex. The corpus luteum of pregnancy was seen in the left ovary. The right ovary was malpositioned and appeared elongated. The upper pole was attached superior to the common iliac vessels. Extra-uterine gravidity (EUG) in a heterotopic, non-communicating right fallopian tube. Careful exploration and dye injection failed to disclose any connection between the heterotopic fallopian tube and the uterus. The heterotopic right fallopian tube was resected. Microscopic examination revealed a hematosalpinx and multinucleated cells typical of syncytiotrophoblast. The postoperative course was uneventful. A postoperative pyelogram confirmed absence of the right kidney and collecting system. The incidence of EUG is approximately 16 in 1000 pregnancies and has increased five-fold between 1970 and 1987 according to the statistics of the CDC (1). The prevalence of all congenital uterus anomalies is on average 0.5% among women in the general population but data are varying between 0.1% and 3.2% depending on the researcher. If only fertile women are considered, the prevalence of uterus malformations is 0.17% (2). Depending on the degree of expression, a considerable number of malformations can arise. Several authors have suggested classifications including the clinical classification of the American Fertility Society (1988). The classification of Buttram and colleagues appears particularly relevant to us because it simultaneously considers both clinical and embryological perspectives (3). Buttram uses a classification with six subgroups (Table I). A unicornuate uterus forms when the development of a paramesonephric duct is impaired. The exact incidence is unknown but figures range from 2.5% to 13% (4). Because unicornuate uterus is a rare anomaly and as no simple screening technique exists, prospective research cannot be done. Therefore the current knowledge depends on small retrospective studies or on case reports. An EUG in a heterotopic, non-communicating tube with a unicornuate uterus and associated kidney agenesis is a rarity. Only a few case reports are found in the literature (5–7). Brown and co-workers (6) described an EUG in a heterotopic tube, left, with a unicornuate uterus, in which the heterotopic tube was located in immediate physical proximity of an also heterotopic corpus luteum bearing ovary. Consequently, a transperitoneal sperm migration occurred. In another case the exact localization of the ovary remained uncertain (7). Here we found the corpus luteum on the left, in combination with a heterotopic fallopian tube on the right. This points to an ovulation on the side opposite to the heterotopic tube. Because the EUG was localized in the right tube and this tube had no relationship to the uterus, a transperitoneal migration must have occurred. Whether this was a transperitoneal migration of sperm and oocytes or a migration of the fertilized ovum, remains uncertain. A transperitoneal migration appears plausible if one considers that in 16% of EUGs a contra-lateral corpus luteum is found. Beyth and co-workers (8) demonstrated in an animal model that a direct contact between the fimbria and the ovary is not essential for ovum reception. It remains unresolved if 'chemotactic' factors that attract the sperm or the fertilized ovum across the peritoneum in the direction of the heterotopic (or contra-lateral) tube are involved.