A ruptured ectopic pregnancy is a gynecological emergency. This diagnosis is rarely missed in resource-rich settings. In this case report, we discuss the human fallibility of diagnosing a ruptured ectopic pregnancy in an atypical and unusual patient presentation. In this case, the patient presented with a chronic ruptured ectopic pregnancy and simultaneous vanishing twin syndrome (VTS) in the setting of a spontaneously conceived triplet heterotopic pregnancy (HP). All three of these conditions are uncommon diagnoses and the rarity of these conditions in combination presented a challenge for the diagnostician.

A 31-year-old Gravida 2 para 1 Hispanic female presented to the emergency department at her local hospital complaining of a 1-month history of left lower quadrant pain, vaginal bleeding, generalized abdominal cramping pain, nausea, and vomiting. Her last menstrual period was eight weeks prior to the presentation. This was the patient’s first medical encounter since her positive home pregnancy test.

The patient reported regular menstrual cycles every 30 days with 5–7 days of bleeding and no hormonal contraception use within the last year. She denied a history of sexually transmitted infections or pelvic inflammatory disease. Her obstetric history included an uncomplicated term spontaneous vaginal delivery. She denied the use of assisted reproductive technology (ART) to conceive this pregnancy. She had no significant medical history, surgical history, or social history.

On presentation, the patient was afebrile, normotensive, non-tachycardic, and appeared comfortable. Abdominal exam revealed tenderness to palpation of the lower quadrants bilaterally with no rebound or guarding. Pelvic exam revealed 5 mL of dark red blood in the vault with no active bleeding. A bimanual exam showed an anteverted 8-cm uterus, 1 cm cervical dilation, no adnexal tenderness, and no palpable masses.

On transvaginal ultrasound, the uterus measured 10.0 × 9.0 × 7.0 cm with two intrauterine gestational sacs. Sac A contained echogenic material with no fetal pole. Sac B showed a fetal pole with a crown-rump length measuring 22.58 mm corresponding to a gestational age of eight weeks and four days and a fetal heart rate of 167 bpm. A lambda sign, characteristic of a dichorionic diamniotic twin pregnancy, was observed between the gestational sacs Neither ovary was identified on the ultrasound. A solid-appearing isoechoic focus, with no internal vascularity and measuring 5.8 × 4.8 × 5.0 cm, was observed posterior to the uterus (Figure 1). Free fluid was not noted. The patient’s laboratory values included a hemoglobin of 10.5 g/dL, hematocrit of 31.4%, white blood cell count of 11,500 mL, and beta-human chorionic gonadotropin (β-hCG) of 93,303.60 mIU/mL.

Given concern for possible ovarian torsion, laparoscopy was performed. Heterotopic pregnancy was not considered for the preoperative differential diagnosis. On entry into the abdominal cavity, 200 mL of clotted fibrinous blood was noted in the pelvis, surrounded by adhesions between the left fallopian tube, left ovary, posterior uterus, and anterior rectum. The left fallopian tube was dilated and ruptured with trophoblastic appearing tissue protruding through the wall positioned posterior to the uterus (Figure 2). The left ovary contained a cyst consistent with a corpus luteum. Slow oozing was noted from the left fimbriae. The right fallopian tube and ovary appeared normal. Intraoperative findings were consistent with ruptured ectopic pregnancy and the decision was made to proceed with definitive treatment with left salpingectomy. After the case’s conclusion, the fetal heart rate of sac B was confirmed to be 142 bpm. The left fallopian tube was sent to pathology, confirming ectopic pregnancy.

The patient’s postoperative course was uncomplicated. She was discharged home independently the same day. At 2-week postoperative follow-up, the patient was recovering well. Ultrasound revealed a single gestational sac with cardiac activity. The remainder of the patient’s pregnancy was uncomplicated. She had a term spontaneous vaginal delivery at 38 weeks with the delivery of a healthy male infant weighing 3380 grams. After delivery, the patient provided written consent to publish all medically pertinent information.

This case presents an intersection of two uncommon diagnoses, chronic ectopic pregnancy, and VTS, with an exceedingly rare diagnosis, spontaneous heterotopic triplet pregnancy. The rarity of these conditions in combination presents a challenge for the diagnostician. We will discuss separately the incidence, clinical presentation, and diagnostic challenges of these conditions.

The incidence of twin HP is 1/30,000 among patients who conceived spontaneously and 1.5/1000 among patients who used assisted reproductive technology [1]. Due to the rarity of triplet HP, there are no data on its incidence. At the time of publication of this article, there have been 11 documented cases in the literature of spontaneously conceived triplet HP pregnancy [2],[3],[4],[5],[6],[7],[8],[9],[10],[11],[12] (Table 1). The majority of these cases presented in the first trimester, while only two occurred in the second trimester at 15 and 18 weeks. Our case is the only documented triplet HP case that presented with acute abdominal pain, overt vaginal bleeding, and VTS at the time of initial presentation. Of note, the case report published by Arsala et al. describes a triplet HP case with VTS. However, the VTS was diagnosed eight days after surgical treatment and was not present at the time of initial presentation with triplet HP.

Among ectopic pregnancies, 20% are classified as chronic. Chronic ectopic pregnancy (CEP) is an ectopic pregnancy with a growth pattern characterized by a protracted cycle of microvascular trauma, bleeding, and thrombus formation that culminates in an enlarging pelvic hemocoel. The theorized mechanism of chronicity is that the trophoblastic invasion impacts terminal vascular branches, which results in slow bleeding that can be outpaced by the coagulation cascade [3]. The chronicity of the condition can cause an atypical presentation with poorly localized, intermittent, dull pain. This presentation contrasts sharply with the classic presentation of acute ruptured ectopic pregnancy which presents with constant, sharp adnexal pain making diagnosis difficult. Further confounding the diagnosis, CEP can present with undetectable serum β-hCG and usually will not present with free fluid on pelvic ultrasound, which can be falsely reassuring [13]. The diagnosis is usually made during evaluation of the amorphous adnexal mass via diagnostic laparoscopy [14]. Of note, information on CEP is sparse in mainstream didactic literature. Neither the ACOG Practice Bulletin, PubMed StatPearls, nor UpToDate articles on ectopic pregnancy mention the variant presentation of CEP. Williams Gynecology textbook only has two paragraphs dedicated to the topic of CEP [14]. Consequently, many providers may be unfamiliar with CEP and unable to associate a similar clinical presentation with a chronic ectopic pregnancy.

Vanishing twin syndrome occurs in approximately one-third of twin pregnancies and half of triplet or higher-order pregnancies [15]. It is defined as the occurrence of the spontaneous reduction of one or more embryos in a multi-gestation pregnancy, resulting in a reduced number of viable embryos. The majority of epidemiological data on VTS is based on ART-conceived pregnancies, as those pregnancies are more likely to be followed by serial ultrasounds. The clinical presentation of VTS varies from asymptomatic to overt symptoms of vaginal bleeding, cramping, and pelvic pain with a correlating span of physical exam findings from a closed cervix with no bleeding to a dilated and effaced cervix [15]. The proportion of asymptomatic VTS cases to symptomatic VTS cases has not been addressed in the existing literature. Even with overt physical manifestations, the remaining viable pregnancy or pregnancies can be carried to full-term gestation. In this case, the patient’s clinical symptoms, physical exam, and intrauterine ultrasound findings aligned with the diagnosis of VTS. The adnexal mass could not be attributed to VTS, and thus prompted further investigation.

This case presents a diagnostic challenge for several reasons: the rarity of the final diagnosis of triplet HP, chronic ectopic pregnancy presentation, and the distracting presence of a VTS. Fortunately, the presence of a poorly defined pelvic mass, found to be the pelvic hematocele from a CEP, prompted further investigation that culminated in the appropriate treatment. Several key lessons should be gained from this case. First, the astute clinician must understand that statistical improbability does not equate to impossibility. This principle is most salient for medical conditions such as ectopic pregnancy, which when unrecognized can result in fatality. Thus, the statistical improbability of a heterotopic triplet pregnancy should not definitively rule out the diagnosis of ectopic pregnancy. Second, this case unveiled a knowledge gap in our current gynecological graduate medical education system: CEP.