Early conception after adenomyomectomy as a risk factor for intramural pregnancy. Twin implantation following IVF with successful subsequent pregnancy: A case report

A 36-year-old nulliparous woman presented at 8 weeks and 1 day of gestation after in vitro fertilization and embryo transfer (IVF-ET) with a presumed diagnosis of cornual pregnancy, based on transvaginal ultrasound findings. She had undergone an open adenomyomectomy via Pfannenstiel laparotomy five months earlier for symptomatic adenomyosis. Two embryos had been transferred during the IVF cycle. Transvaginal ultrasonography revealed two gestational sacs located in an abnormal position near the uterine fundus, with one showing a fetal pole and cardiac activity, raising suspicion for an atypical ectopic pregnancy ( Fig. 1 ). Pelvic magnetic resonance imaging (MRI) confirmed that both embryos were implanted within the uterine myometrium at the site of the previous surgical scar, without communication with the endometrial cavity. It also demonstrated bowel adhesions to the uterine serosa and thinning of the myometrial layer at the implantation site, consistent with twin myometrial pregnancy ( Fig. 2 ). Fig. 1 Transvaginal ultrasound findings of myometrial pregnancy at 8 + 1 weeks of gestation following IVF-ET. (A) Two gestational sacs with fetal poles are visualized within the myometrium, completely separated from the endometrial cavity. (B) M-mode image showing fetal cardiac activity in one embryo, with a heart rate of 157 beats per minute. (C) Color Doppler image demonstrates prominent peritrophoblastic vascular flow surrounding the gestational sacs, consistent with active trophoblastic invasion. Fig. 1 Fig. 2 Pelvic MRI demonstrating twin myometrial pregnancy. Axial (A), sagittal (B), and coronal (C) T2-weighted images reveal two gestational sacs embedded within the myometrium at the site of the previous adenomyomectomy scar. The surrounding myometrial tissue is markedly thinned, and there is no communication with the endometrial cavity. Fig. 2 Transvaginal ultrasound findings of myometrial pregnancy at 8 + 1 weeks of gestation following IVF-ET. (A) Two gestational sacs with fetal poles are visualized within the myometrium, completely separated from the endometrial cavity. (B) M-mode image showing fetal cardiac activity in one embryo, with a heart rate of 157 beats per minute. (C) Color Doppler image demonstrates prominent peritrophoblastic vascular flow surrounding the gestational sacs, consistent with active trophoblastic invasion. Pelvic MRI demonstrating twin myometrial pregnancy. Axial (A), sagittal (B), and coronal (C) T2-weighted images reveal two gestational sacs embedded within the myometrium at the site of the previous adenomyomectomy scar. The surrounding myometrial tissue is markedly thinned, and there is no communication with the endometrial cavity. Surgical management was planned to prevent potential uterine rupture and to address the ectopic gestation. The operation was performed under general anesthesia in the lithotomy position, utilizing the previous Pfannenstiel incision. After abdominal entry, dense adhesions between the uterus and surrounding bowel were noted, and the myometrium at the implantation site appeared markedly thinned. Dilatation and curettage were then performed, followed by insertion of an 8 Fr Foley catheter to delineate the endometrial cavity. Intraoperative transvaginal ultrasound was first used to localize the ectopic gestational sacs in relation to the endometrial cavity. Based on this localization, uterine incision and enucleation of the masses were performed. After excision, transvaginal ultrasound was repeated to confirm complete removal of the gestational tissue and to assess the integrity of the uterine repair ( Fig. 3 ). Fig. 3 Intraoperative and ultrasound images during surgical management of myometrial pregnancy. (A) Intraoperative image of the uterus, showing the gestational masses embedded within the myometrium at the prior adenomyomectomy scar site before excision. (B) Preoperative transvaginal ultrasound showing a Foley catheter inserted into the endometrial cavity to delineate its boundaries and assist with localization during surgery. (C) Postoperative transvaginal ultrasound confirming complete removal of gestational tissue, with the Foley catheter clearly visible within an empty endometrial cavity. Fig. 3 Intraoperative and ultrasound images during surgical management of myometrial pregnancy. (A) Intraoperative image of the uterus, showing the gestational masses embedded within the myometrium at the prior adenomyomectomy scar site before excision. (B) Preoperative transvaginal ultrasound showing a Foley catheter inserted into the endometrial cavity to delineate its boundaries and assist with localization during surgery. (C) Postoperative transvaginal ultrasound confirming complete removal of gestational tissue, with the Foley catheter clearly visible within an empty endometrial cavity. The patient recovered without complications and was discharged on postoperative day 4. Histopathological examination confirmed the diagnosis of myometrial pregnancy, revealing decidual changes in the endometrium and chorionic villi embedded within the myometrium. To reduce retrograde menstruation and support optimal uterine healing, a 6-month course of gonadotropin-releasing hormone agonist therapy was administered postoperatively. Follow-up imaging demonstrated satisfactory restoration of the uterine wall, and the patient subsequently underwent IVF-ET one year after surgery. She achieved a successful pregnancy, and a mid-trimester MRI evaluation demonstrated no evidence of myometrial thinning or scar dehiscence. The pregnancy progressed without major complications, and she delivered a healthy male infant weighing 2370 g via elective cesarean section at 35 weeks and 6 days of gestation.

The authors received no financial support for the research, authorship, and/or publication of this article.

This case provides clinically relevant insights into the risk of intramural implantation following early conception after adenomyomectomy, particularly in the setting of IVF. It underscores the importance of appropriate timing of conception and careful postoperative counseling. In addition, the combined use of intraoperative ultrasound guidance and endometrial cavity delineation represents a practical and reproducible surgical strategy for fertility preservation. Successful subsequent pregnancy further supports the feasibility of this approach.

Myometrial pregnancy represents one of the rarest and most dangerous forms of ectopic pregnancy, with few cases reported in the literature [5] , [6] . It is typically associated with previous uterine trauma such as cesarean section, myomectomy, or adenomyomectomy, which compromise myometrial integrity and create tracts through which trophoblastic tissue can invade [7] . Assisted reproductive technologies, particularly IVF, have increased the incidence of atypical ectopic implantation, likely related to the embryo transfer process and altered uterine architecture [8] , [9] . The present case is notable in that both embryos transferred during IVF implanted within the scar site of a prior adenomyomectomy, resulting in a twin myometrial pregnancy. This presentation is exceedingly rare. The short interval between surgery and conception is a key feature, as incomplete myometrial healing may have created a vulnerable implantation site. Although no standardized guideline exists, several studies recommend delaying conception for at least 6 to 12 months following deep myometrial resection to reduce the risks of abnormal implantation, uterine rupture, or placenta accreta spectrum disorder [10] . This case therefore underscores the importance of individualized counseling on optimal timing of conception after uterine surgery. The occurrence of twin implantation within the same scar region may be explained by the presence of a localized defect in the myometrium, allowing both embryos to implant within the disrupted area following embryo transfer. This phenomenon supports the role of prior uterine injury and incomplete scar healing in facilitating abnormal implantation within the myometrium [2] , [11] . Diagnosis of myometrial pregnancy remains challenging, as imaging findings can overlap with interstitial or cornual pregnancies [12] , [13] . Proposed diagnostic criteria include (1) a gestational sac completely surrounded by myometrium, (2) absence of communication with the endometrial cavity, and (3) exclusion of tubal pregnancy. In this case, MRI clearly demonstrated these features and provided superior anatomical delineation compared with ultrasound [2] , [14] . The findings reported here support the role of MRI as a valuable adjunct for confirming the diagnosis and guiding surgical planning, particularly in patients with recent uterine surgery [15] , [16] . Management depends on gestational age, viability, depth of implantation, and fertility desire. Although the administration of methotrexate has been tried, medical therapy is often ineffective in deeply implanted intramural pregnancies due to limited vascular accessibility [5] . In the present case, surgical excision was selected given the advanced gestational age, presence of fetal cardiac activity, and deep myometrial involvement. Importantly, the combined use of intraoperative ultrasound and Foley catheter placement was instrumental in delineating the endometrial cavity and avoiding inadvertent entry, thereby facilitating complete excision while preserving uterine integrity. This approach may represent a practical and reproducible technique for fertility-preserving management in similar cases. Future fertility considerations remain critical. Preconception evaluation of scar integrity, such as saline infusion sonography or hysteroscopy, may be beneficial [17] , [18] . In subsequent pregnancies, early confirmation of intrauterine implantation, serial monitoring of myometrial thickness, and individualized delivery planning—including consideration of elective cesarean delivery—are recommended to mitigate the risks of rupture or abnormal placentation.

This article was not commissioned and was peer reviewed.

Mi Jung Kwon contributed to patient care, acquiring the data and drafting the manuscript. Chery Ahn contributed to acquiring the data and revising the article critically for important intellectual content. Eun Min Lee contributed to acquiring and interpreting the data and revising the article critically for important intellectual content. Ok-Ju Kang contributed to patient care, conception of the case report, and revising the article critically for important intellectual content. All authors approved the final submitted manuscript. Patient consent. Written informed consent was obtained from the patient for publication of the case report and accompanying images.

Myometrial pregnancy is an extremely rare and potentially life-threatening type of ectopic pregnancy in which the gestational sac implants within the myometrium, separated from the endometrial cavity or fallopian tubes. It is often misdiagnosed as interstitial or cornual pregnancy [1] , and is most commonly associated with previous uterine trauma, such as cesarean section, myomectomy, or adenomyomectomy [2] . The increasing use of assisted reproductive technologies (ART), particularly in vitro fertilization (IVF), has been associated with a rising incidence of atypical ectopic implantations, likely related to the embryo transfer process and altered uterine architecture [3] . Timely diagnosis and appropriate surgical management are essential to preserve fertility and prevent serious complications such as uterine rupture or massive hemorrhage [4] . This report presents a rare case of twin myometrial pregnancy following IVF in a patient with a recent history of open adenomyomectomy, in which both transferred embryos implanted within the myometrial scar. The case highlights the risk associated with conception soon after uterine surgery and the feasibility of fertility-preserving management.

The authors declare that they have no competing interest regarding the publication of this case report.