In 2019, 23.7 percent of all contraceptive users choose female permanent contraception, that is a total of 219 million women worldwide [1]. Although it is relatively rare, post-sterilization pregnancy occurs. The 10-year cumulative occurrence of pregnancy after all methods of sterilization found by CREST was 18.5 per 1000 women [2]. Common risk factors contributing to ectopic pregnancy include smoking; previous ectopic pregnancies, appendectomy, Chlamydia trachomatis infections, infertility, and adnexal surgeries; failure of intrauterine devices; failure of reversible contraceptives; and pregnancy after female sterilization [3]. In women with retained uterus, abdominal pain mandates a pregnancy test, regardless of previous tubal surgery or sterilization surgery, to exclude the possibility of ectopic pregnancy. This report aimed to provide knowledge on the possibility and occurrence of this rare phenomenon of spontaneous left distal tubal pregnancy despite laparoscopic left partial salpingectomy for sterilization and create awareness of its prevention.

The study was approved by the institutional review board and ethics committee of the Chang Gung Medical Foundation for clinical trials (IRB No.: 201900873B0) (blinded for review) and a waiver of consent was granted.

A 39-year-old woman with an obstetric history of gravida 7, para 3 (all normal spontaneous deliveries), two induced abortions, and a right tubal pregnancy was brought to our emergency department due to sudden-onset lower abdominal pain that started one day before her arrival. She reported regular menstrual cycles; the most recent was five weeks and three days earlier. The patient denied having a history of pelvic inflammatory disease. Her past surgical history included one right tubal pregnancy for which she received an open right salpingectomy (11 years and 3 months ago) and laparoscopic left tubal sterilization (6 years and 7 months ago). The initial physical examination showed stable vital signs. The urine pregnancy test was positive. Laboratory test indicated a serum human chorionic gonadotropin ($\beta$-hCG) level of 1022.05 mIU/mL and a hemoglobin level of 12.5 g/dL. A transvaginal ultrasound exam revealed no evidence of intrauterine pregnancy.

Serum $\beta$-hCG levels after 2 and 5 days were 2239 and 2303 mIU/mL, respectively. Although there was no evidence of intrauterine pregnancy, a heterogeneous 4.0 $\times$ 2.1 cm left adnexal mass with minimal ascites was visible on transvaginal ultrasound. Based on the clinical, imaging, and laboratory findings, ectopic pregnancy was impressed, and the patient was admitted for surgical management.

Three-dimensional laparoscopy intraoperative finding includes a 3 $\times$ 4 cm bulging ectopic pregnancy at the left distal end of the remnant stump in the ampulla region, 100 mL of internal bleeding, and a 3.5 cm gap at the previous left tubal sterilization site (Fig. 1). Both ovaries appeared normal in shape and size. No endometriotic foci or endometrioma was found. Previous salpingectomy region is every close to right infundibulopelvis ligament, mimicking its appearance as a residual right fallopian tube. Our examination confirmed the absence of right fallopian tube, which is compatible with her right salpingectomy history. Following patient’s preference for sterilization, a complete left residual tubal stump excision was done. A histopathological exam confirmed ectopic pregnancy diagnosis in the left distal tubal stump. On postoperative day 1, patient’s $\beta$-hCG level decreased to 914.96 mIU/mL. The patient fully recovered post-operatively and was discharged.

Fig. 1.

Three-dimensional laparoscopic surgery showing a 3 cm $\mathrm{\times }$ 4 cm bulging mass at the left distal end of the remnant stump in the ampulla region. The curly bracket denotes the site of the previous tubal ligation gap.

We previously reported a similar case of spontaneous right distal tubal pregnancy post bilateral laparoscopic sterilization, showing that the incidence of pregnancy after tubal sterilization is extremely rare, and the causative mechanism remains unclear [4]. To have the same medical professionals encounter similar cases in such a short duration is unprecedented at our institution. Hence, we would like to report and discuss the postulated mechanisms.

According to literature, there are three main postulations on the occurrence of ectopic pregnancies at the remnant distal tube after sterilization. All mechanisms center on fistula formation, although they differ with regard to its formation. McCausland found that if the site of laparoscopic coagulation is in close proximity to the endosalpinx of the proximal fallopian tube, the tube may be injured and activate a potential fistula formation. However, if coagulation occurs farther away, only fibrosis ensues [5]. This is of clinical significance because if the surgeon can avoid injuring the proximal isthmic portion of the fallopian tube, the possibility of ectopic pregnancy, endosalpingoblastosis, and fistula formation decreases while the prognosis of laparoscopic tubal sterilization improves. Additionally, Dietl et al. and Creinin & Zite [6, 7] suggested that as time elapses after sterilization, the proximal segment of the oviduct showed natural histological transformations, such as chronic inflammation, luminal dilatation, or plical attenuation. Zuzarte et al. [8] proposed that the endometrial and peritoneal cavities might connect through a persistent lumen in the interstitial portion and distal remnant of the oviduct as a result of insufficient ligation. Because intraperitoneal sperm transmigration exists in almost half of all human pregnancies [2], a residual stump presents a risk for ectopic pregnancy and its reoccurrence. If the distal blunt-ended fallopian tube receives a fertilized ovum but the micro fistula is insufficient in size for the fertilized ovum to pass through, the zygote is unable to reach the uterine cavity for implantation, resulting in an ectopic tubal pregnancy. We can even consider total salpingectomy to prevent ectopic pregnancy. This method has a side bonus to reduce the risk for ovarian cancer. According to studies from Ely et al. [9] and Mills et al. [10], salpingectomy is as safe and efficacious as tubal ligation for sterilization and may be preferred because bilateral tubal ligation can reduce ovarian cancer risk by 13–41% but a dramatic 42–78% in total salpingectomy. Hence, removing fallopian tubes have shown to be an effective prophylaxis measure against ovarian cancer and can be considered in woman who wish to undergo sterilization procedure.

All methods of contraception have a risk of failure. Although rare, an ectopic pregnancy can occur after tubal sterilization. To avoid this possibility, surgical techniques should be used to obliterate the residual canal, including the precise location and depth of electrocautery to prevent fistula formation. Because sperm can migrate transperitoneally, total salpingectomy should be the preferred option for women with no desire to bear children to reduce the risk of ectopic pregnancies associated with residual stumps and this procedure is also an effective prophylaxis measure against ovarian cancer.

CYL, CML, YST, CMC, HJS, LYC, and CJW contributed to the conception and design of the study. CYL and CML contributed to the writing of the manuscript. CYL, YST, CMC, HJS, LYC, and CJW contributed to the acquisition and interpretation of the data. All authors read and approved the final manuscript.

The study was approved by the institutional review board and ethics committee of the Chang Gung Medical Foundation for clinical trials (IRB No.: 201900873B0) and a waiver of consent was granted.

The authors would like to thank the Chang Gung Medical Foundation Institutional Review Board for approving this case report for publication.

This research received no external funding.

The authors declare no conflict of interest.