Intramyometrial Pregnancy with Uterine Rupture at Second-trimester after Frozen Embryo Transfer

We detail a particularly challenging case of a 32-year-old woman with a history of secondary infertility who conceived via frozen embryo transfer (FET) and presented at 14 weeks’ gestation with signs of uterine rupture. The patient, gravida 5, para 0, had been struggling with secondary infertility for 4 years. She conceived after undergoing FET but presented with sudden-onset severe lower abdominal pain at 14 weeks. Her obstetric history included two prior biochemical pregnancies, a left-sided tubal ectopic pregnancy managed through laparoscopic salpingectomy, and one intrauterine missed abortion at 7 weeks, which required dilation and evacuation. Notably, she had no history of caesarean delivery, myomectomy or known congenital uterine anomalies. After 2 years of unsuccessful ovulation induction cycles, the couple pursued assisted reproductive technology. However, she had been diagnosed with diffuse adenomyosis involving the junctional zone on TVS prior to initiating assisted reproduction [ Figure 1 ]. Through in vitro fertilisation (IVF) utilising a gonadotropin-releasing hormone (GnRH) antagonist protocol, they achieved 15 mature oocytes and secured nine grade I embryos. Since the patient’s endometrial thickness was <6 mm on the day of human chorionic gonadotropin (HCG), FET was planned. Two doses of GnRH agonist depot were administered at 28-day intervals prior to endometrial preparation for FET. However, the endometrial thickness did not exceed 5 mm even after giving 12 mg estradiol valerate (EV). Endometrial preparation was challenging due to adenomyosis, but after two unsuccessful attempts, satisfactory thickness was achieved with a combination of tamoxifen and EV. Two grade 1 quality cleavage-stage embryos were transferred. Serum β-hCG measurements taken 14 days post-embryo transfer indicated a level of 106 mIU/mL, with appropriate doubling after 48 h. TVS at 6 weeks 6 days confirmed a live intrauterine singleton pregnancy located in the upper uterine cavity [ Figure 2 ]. Follow-up scans at 9 weeks showed normal foetal growth and cardiac activity, and first-trimester screenings were reported as normal. However, the patient subsequently presented at 14 weeks with acute abdominal pain. At 14 weeks of gestation, the patient presented with acute, generalised abdominal pain and exhibited severe pallor (haemoglobin-5.6 g/dL), hypotension (blood pressure 90/60 mmHg) and tachycardia (heart rate 110 bpm), alongside diffuse tenderness and guarding. Transabdominal ultrasound revealed moderate free fluid in the peritoneal cavity and absent foetal cardiac activity. A diagnosis of intra-abdominal bleeding with a suspected pregnancy-related complication led to an emergency diagnostic laparoscopy. On laparoscopic entry, approximately 800 mL of hemoperitoneum was noted. A mass-like lesion was identified on the posterior wall of the uterus, just below the fundus, obscured by omentum. After separating the omentum, a tear measuring 4–5 cm was observed [ Video 1 ]. A foetus was located in the posterior myometrial wall and was on the verge of expulsion [ Figure 3 ]. The removal of placental tissue proved particularly challenging due to its deep embedding within the myometrium [ Figure 4 ]. Attempts to separate the placenta resulted in significant bleeding, necessitating a conversion to laparotomy for better exposure and haemostatic control. The placenta was carefully separated from the myometrial bed, and it was noted that there was no communication between the placental bed and endometrial cavity, and the uterine myometrial rent was repaired in two layers. Transvaginal sonography showing diffuse adenomyosis involving the junctional zone, identified prior to initiation of assisted reproductive treatment Transvaginal sonography at 6 weeks 6 days showing a live intrauterine singleton pregnancy located in the upper uterine cavity Transvaginal sonography revealed the fetus located within the posterior myometrial wall, on the verge of expulsion Intraoperative image showing the fetus in the abdominal cavity and placental tissue in the myometrium

Intramural pregnancy is amongst the rarest and most challenging variants of ectopic gestation, defined by the implantation of the embryo entirely within the myometrial wall, without any communication with the endometrial cavity or adnexal structures.[ 1 ] Accounting for <1% of all ectopic pregnancies, its diagnosis is particularly elusive.[ 2 ] Early transvaginal sonography (TVS) often misinterprets intramural pregnancy as a normally implanted intrauterine gestation, thereby delaying diagnosis until the onset of serious complications such as uterine rupture.[ 3 ] The incidence of such aberrant implantation is observed to be higher in pregnancies achieved through assisted reproductive technologies (ART).[ 4 5 ] Contributing factors may include iatrogenic trauma from prior uterine interventions–such as caesarean sections, myomectomies and curettage–along with conditions such as adenomyosis or altered uterine architecture, which may promote abnormal embryo migration or deep trophoblastic invasion.[ 6 ] Despite recognition of these risk factors, intramural pregnancies remain underdiagnosed in clinical settings due to their nonspecific imaging features and infrequent occurrence.[ 7 ] While uterine rupture during the first or early second trimester is typically associated with prior uterine surgery, such as caesarean delivery or myomectomy,[ 8 ] intramural pregnancies can rupture even in uteri with no prior structural compromise and often do so with minimal or no prodromal symptoms.[ 9 ] When rupture occurs, it frequently leads to catastrophic outcomes, including massive intra-abdominal haemorrhage, hypovolemic shock and perinatal mortality, necessitating prompt surgical management.[ 10 ]

Intramural pregnancies represent an extraordinary obstetric challenge due to their rarity and the complexity they introduce in management, particularly concerning early diagnosis and surgical intervention in cases of rupture. This case illustrates the critical importance of vigilance in patients with risk factors, especially those utilising ART, and highlights the need for thorough radiological evaluations to facilitate timely diagnosis and prevent catastrophic outcomes. A multidisciplinary approach in managing such patients may improve both maternal and foetal outcomes. MK: Conceptualisation, data curation and writing – original draft. PP: Formal analysis and writing–review and editing. DK: Methodology. SS: Conceptualisation, data curation, methodology and writing– review and editing. The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given her consent for her images and other clinical information to be reported in the journal. The patient understand that name and initial will not be published and due efforts will be made to conceal identity, but anonymity cannot be guaranteed. There are no conflicts of interest. The data supporting the findings of this study are available from the corresponding author upon reasonable request.

Uterine rupture in early gestation is rare but potentially fatal, typically linked to prior uterine surgery.[ 1 2 3 ] However, abnormal implantations such as intramural pregnancy, though extremely uncommon, can also lead to rupture even in an unscarred uterus. In the present case, three significant risk factors were identified: a history of D and C, adenomyosis, and an IVF pregnancy. The intramural pregnancy may have resulted from trophoblastic invasion through a microscopic tract left by prior instrumentation or implantation within a junctional zone adenomyotic lesion in the fundo-posterior wall. Similar mechanisms have been suggested in reported cases, including those where adenomyosis was implicated as a nidus for implantation. These findings are consistent with a review of 56 cases by Chen et al ., which revealed that over 83% of patients with intramural pregnancy had a history of prior uterine or endometrial surgery, supporting the hypothesis that uterine trauma plays a central role in the pathogenesis.[ 11 ] In our case, TVS failed to detect the abnormal implantation, likely because of the proximity of the gestational sac to the fundal endometrium, which gave the impression of a normal intrauterine pregnancy. This diagnostic challenge aligns with the observations of Liu and Wu, who reported that preoperative diagnosis of intramural pregnancy is often difficult and frequently only made intraoperatively.[ 12 ] Furthermore, Chen et al . also identified that gestational age beyond 10 weeks and a fundal location of the gestational sac are significant predictors of uterine rupture, with odds ratios of 8.0 and 7.0, respectively.[ 11 ] This finding is consistent with our case, where rupture also occurred at 14 weeks of gestation in the fundal implantation site, supporting the notion that these factors may contribute substantially to the risk of uterine rupture. In most reported cases of second-trimester uterine rupture due to intramural pregnancy, hysterectomy has often been necessary to control haemorrhage, with reported rates as high as 14.3% when diagnosis was delayed.[ 6 ] However, in our case, the surgical team was able to preserve the uterus through timely intervention, meticulous haemostasis and layered uterine repair. This favourable outcome highlights the critical importance of early recognition and individualised management in such complex cases. Clinicians should maintain vigilance when evaluating patients with risk factors such as prior uterine trauma, adenomyosis or ART-related pregnancies. The use of advanced imaging modalities, including high-resolution ultrasound and MRI, may aid in earlier diagnosis and guide appropriate management strategies to optimise maternal outcomes and preserve fertility.