Second-trimester ovarian pregnancy mimicking intrauterine pregnancy and causing hemorrhagic shock in surgery: a case report and review of the literature.

A 29-year-old woman, gravida 7, para 3, abortus 3, with a history of three cesarean sections was referred from a primary hospital to our center for the termination of her pregnancy. The patient was from an ethnic minority background, married, had a secondary school education, and was non-employed. In addition to three cesarean sections, she also had three medical abortions, two of which required a dilation and curettage due to retained products of conception. She had no comorbidities and family history was uneventful. The patient cannot recall the exact date of her last menstrual period. About two months ago, she visited a maternal and child health hospital due to mild nausea and vomiting.An ultrasound performed at that facility was reported to the patient as confirming an “intrauterine pregnancy,” although the detailed report was not available for our review. The patient did not pursue further prenatal care thereafter and reported an uneventful course without abdominal pain, vaginal bleeding, or discharge. In the second trimester, the patient considered her pregnancy unplanned and requested to terminate. She initially visited the aforementioned maternal and child health hospital, which considered her a high-risk pregnant woman and recommended that she be treated at a higher-level hospital. The patient instead visited to a private primary hospital. The ultrasound at that hospital indicated: “Intrauterine mid-trimester singleton pregnancy with a live fetus, equivalent to 20 weeks in size; the lower edge of the placenta is adjacent to the incision in lower segment of the anterior uterine wall; a hypoechoic area (20 × 7 mm) at the lower segment of the anterior uterine wall incision, suggesting a scarred niche.” A routine blood test revealed a hemoglobin level of 8.3 g/dL. Due to these multiple risk factors, the patient was subsequently referred to our center. Upon admission, the patient had no obvious symptoms. Physical examination revealed that the patient’s height was 150 cm, weight was 38.3 kg, and body mass index (BMI) was 17.0 kg/m 2 . Obstetric examination showed a symphysial-fundal height of 22 cm, which was consistent with the gestational age. The cervix was long, closed, posterior, and firm in consistency, which is typical in intrauterine pregnancy at this gestational age. Due to the early gestational age, the fetal presentation was not documented in the medical records. The ultrasound (Fig.  1 ) indicated “Intrauterine singleton pregnancy with a live fetus, fetal development equivalent to 20 + weeks, in a cephalic presentation. The placenta is located on the anterior left wall, with the lower edge of the placenta covering the internal cervical os. The amount of amniotic fluid and the Doppler spectrum of the umbilical artery are within the normal range.” Uterine artery Doppler was not evaluated in this examination. The routine blood test showed a hemoglobin level of 7.8 g/dL and a hematocrit (Hct) of 0.28. Fig. 1 Ultrasonographic images. A Cephalic presentation; B The placenta appeared to cover the internal cervical os Ultrasonographic images. A Cephalic presentation; B The placenta appeared to cover the internal cervical os The patient was orally administered mifepristone, followed by an ultrasound-guided intra-amniotic injection of 100 mg of ethacridine lactate. The injection was prepared by diluting the contents of two ampoules (2 mL:50 mg each) of ethacridine lactate with normal saline to a total volume of 10 mL, in accordance with our institutional protocol for mid-trimester termination [ 10 – 12 ]. The process of intra-amniotic injection was uneventful and without complications. However, after 72 h, the patient still showed no significant signs of labor, so an additional intra-amniotic injection of 100 mg of ethacridine lactate was administered. This procedure also went smoothly without any particular issues. Considering the patient’s low body weight, combined with anemia, and the risk of massive bleeding during labor, 1.5 units of red blood cells were transfused. 24 h after the second intra-amniotic injection, the patient complained of significant lower abdominal pain, which was severe. On physical examination, blood pressure was 104/61 mmHg, heart rate was 100 bpm, there was suspected tenderness in the lower abdomen without rebound tenderness, the external genitalia were clean and dry, and the cervix was not dilated. An urgent ultrasound indicated a possible ectopic pregnancy in the abdominal cavity, with fetal development equivalent to 20 + weeks; there were no abnormalities in the uterine structure, and no pregnancy echo was seen inside the uterine cavity. Considering the patient’s scarred uterus, the possibility of uterine rupture could not be ruled out, so a laparotomy was performed immediately. The surgery involved a vertical incision in the lower abdomen. Upon opening the abdominal cavity, a giant cyst was observed with a smooth surface, tortuous and dilated blood vessels, containing fluid and a fetus. Attempts to explore the boundaries of the cyst were unsuccessful, and the uterus could not be located. A small incision was made in avascular area of the cyst and a dead fetus approximately 20 weeks in size was removed, with the placenta unable to be delivered. When the cyst shrank, it was identified as the left ovary, densely adherent to the abdominal wall, pelvic wall, and omentum; the left fallopian tube was stretched over the cyst but appeared macroscopically normal and intact; the uterus was normal in size and appearance; the right adnexa appeared normal (Fig.  2 B); there was no fluid found in the pelvic cavity. After the removal of the dead fetus, the left ovary still measured about 15 cm in diameter, soft in texture, with visible dilated blood vessels on the surface. The placenta was attached to the ovary with indistinct boundaries (Fig.  2 A). Therefore, the diagnosis of an ovarian pregnancy was established and a left salpingo-oophorectomy was performed. Due to the dense adhesion of the left ovary to the surrounding tissues, a left ureteral stent was inserted. The diagnosis of an ovarian pregnancy was further confirmed by postoperative histology (Fig.  3 ). Fig. 2 Surgical findings. A The placenta was attached to the ovary with indistinct boundaries; B The uterus and right adnexa were normal in size and appearance Surgical findings. A The placenta was attached to the ovary with indistinct boundaries; B The uterus and right adnexa were normal in size and appearance Fig. 3 Pathological findings: placental villous tissue within ovarian tissue. A Low-power view (×4 magnification); B High-power view (×10 magnification). Blue arrow: ovarian tissue; black arrow: placental villi Pathological findings: placental villous tissue within ovarian tissue. A Low-power view (×4 magnification); B High-power view (×10 magnification). Blue arrow: ovarian tissue; black arrow: placental villi The patient was admitted with significant underweight (BMI 17.0 kg/m 2 ) and pre-existing anemia (hemoglobin 7.8 g/dL). Intraoperative difficulties and significant bleeding occurred, leading to hemorrhagic shock during the surgery, with the lowest blood pressure recorded at 56/39 mmHg and the highest heart rate at 170 bpm. The total duration of the surgery was 3 h and 40 min, with a total blood loss of 2000 ml. The patient received 6 units of red blood cells, 1000 ml of plasma, and 10 units of cryoprecipitate, with an intravenous fluid intake of 2550 ml and a urine output of 300 ml. Postoperatively, the patient was transferred to the intensive care unit (ICU) for close monitoring. Her vital signs remained stable, allowing for a gradual tapering and eventual discontinuation of vasoactive medications. Mechanical ventilation was ceased 22 h after the operation. On the second day after surgery, she received another transfusion of 2 units of red blood cells. She was then transitioned back to a general ward on the third postoperative day and was discharged on the fifth postoperative day.

An ectopic pregnancy happens when a blastocyst implants outside the uterine cavity, typically in the fallopian tubes. Ovarian pregnancies, which are quite rare, occur in approximately one out of every 7,000 pregnancies [ 1 ]. The diagnosis of an ovarian pregnancy is challenging due to its nonspecific manifestations. Although ultrasound is useful in identifying ectopic pregnancies, differentiating between ovarian and tubal pregnancies by ultrasound is difficult, often necessitating laparoscopic examination for a conclusive diagnosis [ 2 ]. Most ovarian pregnancies are identified in early pregnancy, which are usually managed by laparoscopic ovarian wedge resection or methotrexate administration [ 2 – 4 ]. An undiagnosed or unmanaged ovarian pregnancy may lead to rupture, hemorrhagic shock, and even pose a threat to life [ 5 ]. Ovarian ectopic pregnancies in the second trimester are extremely rare. Most reports in the literature are case reports, with patients exhibiting significant clinical heterogeneity, making diagnosis challenging and clinical management difficult [ 6 , 7 ]. However, the rupture of an ovarian ectopic pregnancy at a later stage of pregnancy poses a greater risk than those that rupture in the early stages, being more likely to cause severe internal bleeding, hypovolemic shock, respiratory and circulatory disturbances, and other life-threatening complications, which require particular attention from clinicians [ 7 – 9 ]. Here we describe an unusual case of second-trimester ovarian pregnancy mimicking intrauterine pregnancy, which caused hemorrhagic shock during the laparotomy. A further discussion of diagnosis and management on this rare entity is also performed based on a review of the existing literature.

Ovarian pregnancy, characterized by the implantation of a fertilized ovum within the ovary, represents a rare variant of non-tubal ectopic pregnancies that do not involve the fallopian tubes [ 1 ]. The majority of existing research on this topic is comprised of individual case studies. According to a systemic review conducted within the specified timeframe from 2011 to 2022, a mere 82 instances of ovarian pregnancies have been documented in the literature [ 13 ]. The prevalence of ovarian pregnancy is reported to be between 0.03% and 0.09% relative to the total number of pregnancies, with variations observed across different demographic studies [ 14 – 16 ]. Despite the lack of a definitive understanding of the pathogenesis of ovarian pregnancies, several potential risk factors have been identified, such as the use of assisted reproductive technologies, intrauterine device usage, coexisting endometriosis, pelvic adhesions, and a history of abdominal surgeries [ 2 , 6 ]. The clinical manifestation of ovarian pregnancy closely mirrors that of tubal ectopic pregnancy, with symptoms typically encompassing amenorrhea, lower abdominal pain, and vaginal bleeding. In cases where ovarian pregnancy rupture occurs, resulting in substantial intra-abdominal hemorrhage, the clinical presentation can include symptoms indicative of hemorrhagic shock [ 1 , 2 ]. In fact, ovarian pregnancies are more prone to intra-abdominal hemorrhage and life-threatening conditions compared to tubal ectopic pregnancies. It is indicated that ultrasonography revealed hemoperitoneum in 80% of ovarian pregnancy cases, and a separate investigation reported that 30% of these cases experienced circulatory failure [ 17 , 18 ]. Therefore, the prompt and precise diagnosis of ovarian pregnancy, followed by appropriate management, is crucial for enhancing patient prognosis. The Spiegelberg criteria for diagnosing ovarian pregnancy encompass several key features: attachment of the ovary to the uterus via the ovarian ligament, the gestational sac being situated within or in proximity to the ovary, the fallopian tube remaining intact but with detached fimbria, and the presence of ovarian tissue in the histological specimen [ 1 ]. The current case fulfilled all these criteria of ovarian pregnancy. Intraoperatively, although the left fallopian tube was stretched and edematous, it remained macroscopically intact with no evidence of rupture or tubal pregnancy. However, due to the symptomatic similarities between ovarian and tubal pregnancies, preoperative diagnosis of ovarian pregnancy poses a significant challenge. A large proportion of ovarian pregnancies are not confirmed until the surgery. As for the management, surgical intervention is essential, with a current preference for minimally invasive laparoscopic procedures over traditional laparotomy in recent years. The optimal surgical approach involves the removal of the ectopic pregnancy while maintaining the integrity of the ovary. In cases of larger or more advanced ovarian pregnancies, ovarian wedge resection may be necessary, and oophorectomy should be considered only in extreme circumstances [ 2 ]. Additionally, a success rate of 60% has been documented in the medical management of ectopic ovarian pregnancies using methotrexate [ 19 ]. Ovarian pregnancies in second-to-third trimester, however, are even rarer cases. As shown in Table 1 , currently there are only six documented cases of ovarian pregnancies at advanced gestational ages in the English literature. In these six cases, the patients were all multiparous women. Specifically, two cases of ovarian pregnancies reached full term, with one resulting in the live birth of a female infant [ 20 ]. The other case, however, was complicated by a stillbirth, which was identified and surgically managed during a subsequent pregnancy [ 21 ]. Of the remaining four cases, all were diagnosed during the second trimester of pregnancy [ 7 – 9 , 22 ]. Although several risk factors for ovarian pregnancy have been mentioned above, among these patients with advanced gestational age, only one case had a history of contraceptives use [ 21 ], while no significant risk factors were identified for the other patients. Clinical manifestations among the cases varied significantly. Two cases presented with abdominal pain and vaginal bleeding, similar to those of tubal ectopic pregnancies [ 9 , 22 ]. One case followed a course akin to a normal intrauterine pregnancy [ 20 ]. A full-term ovarian pregnancy with a stillbirth was characterized by an abdominal mass [ 21 ], while two cases initially presented with symptoms of hemorrhagic shock [ 7 , 8 ]. The atypical and nonspecific nature of these manifestations render the diagnosis of ovarian pregnancy particularly challenging. In only one of the six cases, the possibility of ovarian pregnancy was considered preoperatively based on the findings from magnetic resonance imaging (MRI) [ 20 ]. As for the surgical interventions, although the optimal management of early ovarian pregnancies typically involves the excision of the ectopic pregnancy or ovarian wedge resection [ 1 ], in these cases at advanced gestational ages, oophorectomy or salpingo-oophorectomy was invariably required. Additionally, intraoperative hemorrhage was often substantial, leading to blood transfusions in four cases. Table 1 Summary of the cases in the literature Cases Region Maternal age Past pregnancy history Risk factors Gestational age of ovarian pregnancy (week) Manifestations Time of diagnosis Rupture of ovarian pregnancy Hemoperitoneum Hemorrhagic shock Blood loss during surgery Blood transfusion Operation performed Outcome Agarwal N et al. 2020 [ 20 ] India 35 Gravida 9, para 4 No history of contraception or IUD. No history of infertility treatment, endometriosis or tubal surgery and recurrent pelvic infections. Term pregnancy Mimicking normal intrauterine pregnancy, painless spotting Preoperative diagnosis of peritoneal or ovarian pregnancy by MRI No No No 2500 ml yes Left salpingo-oophorectomy and hysterectomy Live birth; postoperative recovery uneventful Elwell KE et al. 2015 [ 22 ] USA 37 Multigravida, single parous No history of pelvic infections, infertility treatments, current IUD or abdominal surgeries 16 + 4 Mild abdominal discomfort and intermittent vaginal spotting An ectopic pregnancy in the right adnexa revealed by preoperative ultrasound, and confirmed as ovarian pregnancy during surgery No No No Not mentioned Not mentioned Right salpingo-oophorectomy Postoperative recovery uneventful Shahabuddin AK et al. 1998 [ 21 ] Bangladesh 25 Multigravida with 2 living babies Had used varieties of contraceptives including IUD Term pregnancy Abdominal lump in the past 18 months Diagnosis during surgery No No No Not mentioned Not mentioned Right oophorectomy and left salpingectomy Full term macerated fetus in the ovarian pregnancy; postoperative recovery was uneventful and the intrauterine pregnancy resulted in a term delivery Hwang DW et al. 2020 [ 7 ] Korea 26 Gravida 4, para 2 Not mentioned Second trimester (estimated by fetal weight) Coma, absence of spontaneous breathing and low blood pressure Diagnosis during surgery Yes Yes Yes Excessive bleeding Yes Right oophorectomy Disseminated intravascular coagulation; transferred to the intensive care unit Stanley JR et al. 1994 [ 9 ] USA 34 Gravida 4, para 2 No history of pelvic inflammatory disease, infertility, or use of IUD 19 Several weeks of low abdominal pain and vaginal bleeding Preoperative MRI suspicious of an extrauterine pregnancy. An ovarian twin pregnancy was confirmed during surgery. No No No Approximately 2000 ml Yes Right salpingo-oophorectomy Postoperative recovery uneventful Corrigan KJ et al. 2007 [ 8 ] USA 35 Gravida 3, para 2 Not mentioned 16 + 1 7 h of acute-onset, constant right-sided abdominal pain, shortness of breath, and nausea Diagnosis during surgery Yes Yes Yes Not mentioned Yes Right salpingo-oophorectomy Postoperative recovery uneventful IUD Intrauterine device Summary of the cases in the literature IUD Intrauterine device In the case reported here, the patient was a 29-year-old multiparous woman with a history of three cesarean sections and no other risk factors. The pregnancy was uneventful, with the patient under the impression of an intrauterine pregnancy. It was not until the administration of ethacridine lactate for pregnancy termination in the second trimester that she experienced lower abdominal pain, which led to the urgent laparotomy. The diagnosis of ovarian ectopic pregnancy was ultimately established during the surgery. Although the surgical findings confirmed that the ovarian pregnancy had not ruptured, the patient, who was extremely thin with preoperative anemia, faced severe adhesions, difficult manipulation, and significant blood loss during surgery, resulting in hypovolemic shock. Due to the surgical challenges, it was not feasible to excise the gestational tissue while preserving the affected ovary. Consequently, a left salpingo-oophorectomy was performed, with the surgical approach being consistent with that reported in the literature. The patient in the current case ultimately made a full recovery and was discharged smoothly. Upon reviewing this case, there are valuable lessons to be learned in clinical management. Firstly, the majority of ovarian pregnancies are detected during the early stages of pregnancy [ 2 , 16 ]. As pregnancy progresses into the middle to late stages, ultrasonographers usually focus on the fetus and its associated structures. Moreover, ovarian pregnancies at advanced gestational ages are exceedingly rare, making them difficult to identify through ultrasound. Uterine contour should be routinely assessed and documented in antenatal ultrasound examinations, as irregularities may indicate an ectopic implantation. Transabdominal ultrasound should be performed with a full bladder, which allows for an optimal acoustic window and improved visualization of pelvic structures. In early pregnancy, transvaginal ultrasound should be performed for better delineation of the adnexa and accurate localization of the gestational sac. Secondly, when a patient’s presentation does not align with a typical intrauterine pregnancy—for example, when the patient does not respond to the first dose of abortion-inducing medications, intrauterine pregnancy should be evaluated and the possibility of a rare ectopic pregnancy should be considered. Thirdly, this patient was severely underweight and anemic, with severe adhesions and abundant blood supply from the pregnancy tissue encountered during surgery, ultimately leading to hemorrhagic shock. If pre-intervention measures such as multiple small-volume blood transfusions had been administered to improve the overall condition and enhance her tolerance to bleeding, the risk and severity of hemorrhagic shock could potentially have been reduced.

Ovarian pregnancies at advanced gestational ages are exceedingly rare in clinical practice. The infrequency of this condition, coupled with the nonspecific nature of its symptoms and signs, renders preoperative diagnosis extremely challenging. This can lead to significant intraperitoneal hemorrhage and hemorrhagic shock, thereby posing a severe threat to the patient’s life. Consequently, when a patient’s clinical manifestations do not correspond with those of a typical intrauterine pregnancy, the potential for this rare form of ectopic pregnancy should be taken into account.