Introduction

An ectopic pregnancy (EP) is an implantation of the blastocyst outside the uterine cavity. The overall incidence of EP increased during the mid-twentieth century, plateauing at approximately 2 % in the early 1990s [1]. It is difficult to determine the current incidence of EP because inpatient hospital treatment of EPs has decreased and data from hospitalization records are not available. Widespread use of reproductive techniques, such as cleavage-stage embryo transfer and ovulation induction, is thought to elevate the risk of EP. The prevalence of EP has been increased to 2–11 % by assisted reproductive technology (ART) [2, 3]. In patients undergoing ovulation induction, the reported incidence of EP is approximately 3 % [4]. The location of EPs vary, but the vast majority (>95 %) are found in the fallopian tubes. In spite of the increased incidence of EP after ovulation induction and ART, abdominal pregnancy is still a rare phenomenon. Therefore, a patient with two simultaneous primary EPs in different locations, the abdominal cavity and the fallopian tube, is an extremely rare case. The present case involves EPs that developed during an ovulation induction treatment cycle.

Case report

A 26-year-old Japanese woman, gravida 0, para 0, had visited an outside hospital with sustained high basal body temperature. Her past medical history was nothing. She had undergone her first cycle of controlled ovarian stimulation using 100 mg/day of clomiphene citrate beginning on cycle day 5 and lasting for 5 days. Urinary LH monitoring, determined daily with the use of commercial kits, was used to time intercourse. Pregnancy was confirmed, and it was estimated to be 4 weeks gestation from the day of ovulation. Two weeks later, she visited the hospital again with intermittent abdominal pain in her left lower quadrant and 2 days of vaginal bleeding. An ultrasonographic scan did not detect a gestational sac in the uterine cavity. She was referred to our hospital for a suspected EP. A transvaginal ultrasound examination showed a small gestational sac surrounded by a hematoma and a fetal heartbeat located in the anterior left side of the uterus. Bimanual examination revealed tenderness in the same location. Her serum hCG levels were elevated at 5,349.2 mIU/ml. Based on these findings, she was initially diagnosed with a left tubal pregnancy. Laparoscopic surgery was performed and showed a small amount of hemoperitoneum and an enlarged but unruptured right fallopian tube (Fig. 1). The left fallopian tube was normal, in contrast to our expectations, and no adhesions were observed in the pelvis. A right salpingectomy and hemostasis was performed with monopolar forceps. A thorough abdominal inspection revealed that a small (approximately 1.0–1.5 cm in diameter) hematoma was buried in the vesicouterine pouch adjacent to the left round ligament (contralateral to the hemosalpinx) (Fig. 2), and the mass was completely removed. Histopathological examination confirmed that chorionic villi were seen in both the right salpinx and the hematoma (Fig. 3). The patient had an uneventful postoperative course, and was discharged 5 days after surgery.

Fig. 1
figure 1

Laparoscopic findings of the tubes. Right hemosalpinx (arrow) and intact left fallopian tube are shown

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Fig. 2
figure 2

Laparoscopic findings of the pelvic cavity. Slight hemoperitoneum and peritoneal implant (arrow) adjacent to the left round ligament are shown (a low magnification, b high magnification)

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Fig. 3
figure 3

Histopathological findings of ectopic pregnancy (hematoxylin–eosin stain, a vesicouterine pouch. Chorionic villi in hematoma. Original magnification ×40; b right fallopian tube. Chorionic villi corresponding to first trimester surrounded by decidualized tubal stroma. Original magnification ×12.5)

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Discussion

Timely diagnosis of EPs is essential because they may cause life-threatening hemorrhage. Despite the recent advances in diagnostic imaging apparatus, it is still difficult to accurately diagnose the site of an EP. The sensitivity of transvaginal ultrasound for the diagnosis of EP ranges 69–93 % and is affected by the gestational age, the existence of adnexal masses, and the diagnostic ability of the physician [5–7]. It is not surprising that misdiagnoses occur in cases of absent adnexal masses, such as abdominal pregnancy. Abdominal pregnancy is a rare phenomenon that occurs in approximately 1 in 10,000 pregnancies [8]. It is a serious disease because it is seldom detected until an advanced gestational age or in the event of subsequent severe hemorrhage [9]. Maternal mortality rates associated with abdominal pregnancy have been reported to be in the range 5–12 % [10, 11]. In other report, maternal mortality rate of abdominal pregnancy is estimated to be 7–8 times as high as that of other types of ectopic pregnancy [12, 13]. Fortunately, in the present case, because of the existence of conceptus in the pelvis and the thorough abdominal inspection, we detected the abdominal EP at an early stage and successfully treated the patient.

There are no specific ultrasonographic characteristics of abdominal pregnancies at an early gestational age. The classic ultrasound findings, which can be observed at an advanced gestational age, are the absence of the uterine wall between the bladder and the fetus, poor visualization of the placenta, extrauterine location of the placenta, and a fetus located adjacent to the mother’s abdominal organs [14]. Therefore, magnetic resonance imaging (MRI) and laparoscopy should be considered in the cases of suspected abdominal pregnancy.

The etiology of abdominal pregnancy is thought to involve two mechanisms: (1) direct implantation on the peritoneum (primary abdominal pregnancy) and (2) abortion or rupture of a tubal (less commonly, an ovarian) pregnancy and subsequent re-implantation of the conceptus on the peritoneum (secondary abdominal pregnancy). Most of the abdominal pregnancies are considered secondary. The implantation sites of abdominal pregnancies are mostly the pouch of Douglas and the posterior uterine wall, maybe because adnexa are usually located in these sites [15]. Based on the literature, the following is the suggested diagnostic criteria for primary abdominal pregnancy: (1) intact ovary and fallopian tube, (2) absence of uteroperitoneal fistula, (3) existence of only peritoneal implantation, and (4) early gestational age (which eliminates the possibility of secondary implantation) [16]. Our case had both tubal and peritoneal lesions, which did not fulfill the criteria of primary abdominal pregnancy. However, reproductive technologies such as ovulation induction and ART, which tend to cause multiple pregnancies, are unexpected circumstances in the previous report. This case involved a pregnancy at an early gestational age, making secondary implantation unlikely. Therefore, we think that this case had two distinct pregnancies: a right tubal pregnancy and a primary abdominal pregnancy.

In conclusion, a high index of suspicion is important for diagnosing abdominal pregnancy and reducing the associated morbidity and mortality. Multiple implantation sites should be considered, particularly in the cases with multiple ovulations or embryo transfers.