Granulomatous mastitis during pregnancy with sudden onset of gait difficulty and erythema nodosum: A case report and review of the literature.

Granulomatous mastitis (GM), a benign inflammatory disease of the breast, often mimics breast cancer on presentation. We present a case of GM during pregnancy manifesting as a breast mass, sudden onset of plantar pain, and erythema nodosum (EN). A 31-year-old pregnant Japanese woman, gravida 2, para 1, was referred to our hospital with severe plantar pain on both soles, causing difficulty walking. This pain worsened and EN appeared on both lower legs, followed by a left breast mass. Ultrasound findings suggested malignancy; however, aspiration biopsy confirmed GM. Her arthritis and EN resolved 2 days after commencing oral prednisolone and her walking improved. EN with/without arthritis is commonly associated with GM, especially during pregnancy. The described manifestations with a breast mass are suggestive of this diagnosis.

Resuscitative endovascular balloon occlusion of the aorta: A novel approach for treating amniotic fluid embolism with disseminated intravascular coagulopathy-A report of two cases.

We present two critical cases of life-threatening postpartum hemorrhage (PPH) due to amniotic fluid embolism (AFE) complicated by disseminated intravascular coagulopathy (DIC). These cases are the first to show the effectiveness of resuscitative endovascular balloon occlusion of the aorta (REBOA) for patient survival. In Case 1, the patient, experiencing critical conditions with severe PPH and DIC despite conventional treatments, including rapid blood transfusion and fibrinogen concentrate, was air-transferred to our hospital, where REBOA was promptly employed before hysterectomy was completed. Case 2 involved an ambulance-transferred patient with massive PPH and DIC despite conventional treatments. Prehospital REBOA was performed to prevent cardiac arrest during transfer, and hysterectomy was performed in the hospital. Given the rapid deterioration associated with AFE, REBOA can serve as a bridge until complete hemostasis to maintain vital signs and control bleeding in patients unresponsive to standard therapies before hemostatic interventions or during transfer.

Superb microvascular imaging for assessment of post-cesarean myometrial blood flow from 1 to 4 weeks after operation: A preliminary study.

PURPOSE: To evaluate superb microvascular imaging for measuring puerperal myometrial microvascular blood flows at incisional sites following cesarean delivery. METHODS: Twenty postpartum women (singleton births) were studied: 10 with cesarean and 10 with transvaginal deliveries. All cesarean cases were first operational delivery with lower uterine incision, repaired with double-layer suture. At 1 and 4 weeks postpartum, the uterus was delineated using transvaginal ultrasonography with superb microvascular imaging. Separate regions of interest were created for anterior myometrium of the isthmus and the body. The microvascular flow profile in three circular sampling points placed in a region of interest was quantified and expressed as vascular density. The vascular density ratio of the uterine isthmus to the body was compared between one and four weeks for both groups. Wilcoxon's signed-rank test was used to assess statistical significance (set at p < 0.05). RESULTS: In cesarean deliveries, the vascular density ratio of the uterine isthmus to the body increased from 1 (median: 0.51, range: 0.30-0.68) to 4 weeks (0.99, 0.85-1.60), whereas no changes were noted in transvaginal deliveries. CONCLUSION: Superb microvascular imaging can effectively measure myometrial microvascular blood flow recovery at cesarean incision sites, indicating its potential as a tool for monitoring postpartum wound healing.

Novel application to evaluate endometrial blood flow using transvaginal superb microvascular imaging: A preliminary study describing physiological changes from ovulation to mid-luteal phase.

INTRODUCTION: We aimed to describe physiological changes in endometrial blood flow (minute arterioles running through the endometrium) from ovulation to the mid-luteal phase using superb microvascular imaging. MATERIAL AND METHODS: The study involved 17 women (median age, 32.5 years; first to third interquartile range, 29.8-40.0 years) with regular menstrual cycles who were managed in our institute from 2020 to 2021. The uterus was delineated at the sagittal section using transvaginal ultrasonography incorporated with superb microvascular imaging. For each participant, a total of 28 cycles were observed; 17 cycles observed within one day of ovulation and the implantation period, 5-7 days (D5-7) after ovulation in the same cycle, and nine cycles in which only ovulation was observed, and two cycles in which only D5-7 was observed. Therefore, 26 and 19 images at ovulation and D5-7, respectively, were acquired. Endometrial blood flow was evaluated by depth of the vascular signal in the endometrium and categorized as follows: signals only in the basal layer of the endometrium (grade 1), reaching up to half the endometrium (grade 2), and covering the whole endometrium (grade 3). Changes in the grade of endometrial blood flow from ovulation to D5-7 after ovulation, and the relationship between the grade of endometrial blood flow and the endometrial thickness on ovulation and D5-7 after ovulation, were analyzed. Statistical significance was set at p < 0.05. RESULTS: The endometrial blood flow from ovulation to D5-7 after ovulation during the same menstrual period showed a downgrade in 14 of 17 cycles (82.3%) and no change in the remaining three cycles (17.6%), indicating a decrease in the endometrial blood flow from ovulation to D5-7 after ovulation (p = 0.001). There were differences between the grade of endometrial blood flow and median endometrial thickness on ovulation (grade 1: 5.9 mm, grade 2: 9.1 mm, and grade 3: 11.2 mm); however, no differences in the endometrial thickness were found between the grades on D5-7 after ovulation. CONCLUSIONS: In the normal menstrual cycle, endometrial blood flow decreased from ovulation to the mid-luteal phase, and the endometrial thickness in the ovulatory phase was related to the endometrial perfusion.

Gestational age-related changes in cervical gland length in normal singleton pregnancies from 17 to 36 weeks of gestation.

AIM: To determine the gestational age-related changes in cervical gland length in relation to cervical length (CL) in normal singleton pregnancies. METHODS: We studied 363 women with an uncomplicated singleton pregnancy (188 nulliparous and 175 multiparous women with one or more previous transvaginal deliveries). A total of 1138 cervical gland and CLs were measured longitudinally at 17-36 weeks of gestation using transvaginal ultrasonography along the curvature from the external os to the lower uterine segment and the internal end of the cervical gland area (CGA), respectively. Gestational age-related changes in cervical gland and CLs and their relationships were analyzed using a linear mixed model. RESULTS: Cervical gland and CLs decreased in different ways with advancing gestation depending on parity, and their changes were related to each other. The CGAs in nulliparous women were longer than those in multiparous women at 17-25 weeks of gestation (p < 0.05), but with no differences thereafter. CLs in multiparous women were different from those in nulliparous women at 17-23 and 35-36 weeks (p < 0.05), but there were no differences at 24-34 weeks. The cervix did not shorten compared with the CGA throughout the observational periods in nulliparous and multiparous women. CONCLUSIONS: Shortening of the cervix indicates changes to the lower uterine segment in normal pregnancies. The cervical gland region can be a useful marker representing the true cervix beyond 25 weeks of gestation, irrespective of parity.

Unraveling the enigma: A case of dynamic morphological changes in the niche at 25 weeks of gestation recapitulating the ontogenesis of uterine scar dehiscence.

We present the first report of a case with a peculiar configurational change in the lower uterine segment detected during transvaginal ultrasonography observation over a short period of time at 25 weeks of gestation, predicting the presence of uterine scar dehiscence at term.

A case of ventricular noncompaction associated with heterotaxy and atrioventricular block diagnosed at 15 weeks of gestation using superb microvascular imaging.

We present a case of fetal atrioventricular block, heterotaxy, and ventricular noncompaction observed longitudinally from the first to early second trimesters using B-mode and Doppler imaging, including superb microvascular imaging. At 12 weeks of gestation, the atrial and ventricular rates were 133 and 67 beats/min, respectively, and dextrocardia was noted. At 15 weeks of gestation, detailed sonography revealed ventricular septal defect, interruption of the inferior vena cava, dilated azygos vein, and double-outlet right ventricle. In addition, superb microvascular imaging revealed irregular contours in the anatomical left ventricular wall, indicating prominent trabeculations of the ventricle, which were characteristic findings of ventricular noncompaction. At 21 weeks of gestation, intrauterine fetal death occurred, and the autopsy revealed complex congenital heart disease, including ventricular noncompaction.

Difficulty in prenatal diagnosis of the volvulus of the small intestine: A peculiar clinical course of two cases with massive bowel dilatation and loss of peristalsis.

We report two cases of fetal intestinal volvulus (jejunum in case A, ileum in case B) with massive bowel dilatation and loss of peristalsis, which suddenly appeared in the third trimester. The bowel was dilated to different sizes and there were various echogenic patterns of the intestines in case A and a sausage-like appearance in case B. Case A developed polyhydramnios, whereas case B did not. Among 47 cases of fetal intestinal volvulus (29 articles) in which 32 were diagnosed prenatally, almost all cases with a prenatal diagnosis showed "whirlpool sign" or "coffee bean sign" by sonography and/or findings indicating intestinal hemorrhage. Even without these findings, the presence of dilatation of the intestines and loss of peristalsis occurring in the third trimester were diagnostic clues. The presence of different sizes and various patterns of bowel dilation and hydramnios may be helpful for predicting the involved site of intestinal volvulus.

Missing decidual Doppler signals as a new diagnostic criterion for placenta accreta spectrum: A case described using superb microvascular imaging.

We present a case of a 34-year-old pregnant woman with a prior cesarean delivery presenting with placenta previa. Placenta previa accreta was diagnosed from missing decidual flow signals using superb microvascular imaging (SMI). At 31 weeks' gestation, B-mode ultrasonography showed that the placenta was attached to the anterior uterine segment, extending over the internal cervical os. In normally appearing myometrium, SMI demonstrated double layers of flow signals underneath the placental basal plate, corresponding to myometrial and decidual flows. The thin myometrium located on the bladder where sonolucent zones were not visible revealed three different flow patterns in the Doppler signals underneath the basal plate as follows: double layers (both myometrium and decidual tissues present); a single layer (myometrium alone) or no layers (decidual tissues missing). A cesarean hysterectomy was performed at 37 weeks, and histology confirmed the presence of placenta accreta.

Simple method to distinguish the type of fetal premature contraction using arterial Doppler time interval measurements.

AIM: The purpose of this study was to establish a simple method to distinguish premature ventricular contractions (PVC) from premature atrial contractions (PAC) using a fetal Doppler ultrasound arterial pulse waveform to measure time intervals between sinus node restarting. METHODS: We retrospectively identified 14 fetuses with premature contraction (8 with PAC, 6 with PVC). We measured two distinct parts of time intervals using an arterial pulsed-wave Doppler: the two consecutive waveforms just before the premature contraction (2-V interval) and two consecutive waveforms including the premature contraction (XV interval) to measure time intervals between sinus node restarting. We then evaluated the time difference between the 2-V and XV intervals in PVC compared to PAC. RESULTS: For PVC, the difference between the 2-V interval and the XV interval was significantly shorter than that for PAC. A cut-off point of 33 ms, where a difference ≤33 ms was clearly shown to be associated with a PVC and a difference more than 33 ms signified a PAC was demonstrated. CONCLUSION: The 2-V and XV interval measurements, used to measure time intervals between sinus node restarting, could easily distinguish PVC from PAC in utero. Therefore, this study could potentially be a feasible and effective method for obstetricians or sonographers to employ usefully.

Clues and pitfalls in prenatal diagnosis of classic cloacal exstrophy using ultrasonography and magnetic resonance imaging: A case with sequential observation from 17 to 30 weeks' gestation and literature review.

We observed a case of classic cloacal exstrophy (CE) from 17 to 30 weeks' gestation. At 17 weeks, an omphalocele and single umbilical artery (SUA) were diagnosed with a normal female karyotype on amniocentesis. A pelvic cystic adjacent to SUA, considered to be the bladder at 17 weeks, became swollen to form double cysts at 25 weeks. A phallus-like structure along the lower abdomen was additionally detected, leading to the diagnosis of CE. Fetal magnetic resonance imaging (MRI) at 30 weeks confirmed that the phallus-like structure was of intestinal origin. The presence of a non-visualizable bladder together with abdominal wall defect or omphalocele and an elephant trunk-like deformity are key findings in the prenatal diagnosis of classic CE. Fetal MRI was useful in confirming ultrasonographic findings and obtaining additional findings for the diagnosis of CE. We have discussed clues and potential pitfalls in diagnosing CE, with a review of the literature.

Peculiar blood flow profiles among placental chorionic villous vessels of an abnormally thick placenta in a case of systemic lupus erythematosus characterized using microvascular imaging.

We present a patient with systemic lupus erythematosus receiving long-term steroid therapy, who had myometrial thinning, markedly thickened placenta, and fetal growth restriction (FGR). Blood flow profiles of the myometrium, decidua and placental villous vessels (VV) were described using superb microvascular imaging (SMI) at 35 weeks' gestation. Images showed no decidual blood flow underneath the placenta sitting on a thin myometrium and sparse VV distribution and non-visualization of peripheral VV flow. Emergency cesarean hysterectomy was performed at 36 weeks. Histological findings showed missing decidua on the thin myometrium, which indicated placenta accreta spectrum, and massive perivillous fibrin deposition and increased numbers of syncytial knots in the placenta. We speculated that the thick placenta and peculiar VV flow profiles resulted from congestion of the intervillous space and intervillous underperfusion/low intraplacental oxygenation, respectively, resulting in FGR. Superb microvascular imaging is useful for diagnosing placenta accreta spectrum and understanding the pathophysiology of thick placenta and FGR.

Gestational age-related changes in shear wave speed of the uterine cervix in normal pregnancy at 12-35 weeks' gestation.

Background This study aimed to analyze age-related changes in shear wave speed (SWS) of the normal uterine cervix. Methods We studied 362 women with a normal singleton pregnancy at 12-35 weeks' gestation. The SWS of the cervix was measured using transvaginal ultrasonography at the internal os region of the anterior cervix (IOA), posterior cervix (IOP) and cervical canal (IOC), and at the external os region of the anterior cervix (EOA), posterior cervix (EOP) and cervical canal (EOC). The following parameters were analyzed: (1) time trend of SWS of the individual sampling points, (2) comparison of SWS in the internal cervical region and SWS in the external cervical region, and (3) comparison of SWS between the internal and external cervical regions. Statistical analyses were performed using mixed-effects models. Results The SWS of IOP decreased in bilinear regression, with a critical change in the rate at 22 weeks, whereas the SWS of the remaining points decreased linearly. The estimated values of SWS of IOP at 84, 154 and 251 days were higher than those of IOA and IOC (P<0.001). The estimated values of SWS of IOP at 84 and 154 days were higher than those of EOP (P<0.001). Significant differences between IOP and EOP were shown until 244 days (P<0.05). The estimated value of SWS of IOC at 84 days was higher than that of EOC (P<0.001). Significant differences between IOC and EOC were shown until 210 days (P<0.05). Conclusion The SWS of the uterine cervix in pregnancy decreases with advancing gestation. The SWS of IOP had the highest value among the sampling points with unique characteristics.

Prediction of histological chorioamnionitis and neonatal and infantile outcomes using procalcitonin in the umbilical cord blood and amniotic fluid at birth.

AIM: We aimed to clarify the usefulness of procalcitonin (PCT) in the evaluation of histological chorioamnionitis (CAM) and in the prediction of neonatal and infantile outcomes as a reference of interleukin-6 (IL-6). METHODS: Subjects were 36 singleton pregnant women delivered at 22-37 weeks' gestation due to threatened premature delivery and/or preterm premature rupture of membranes. Cases were classified into the CAM and non-CAM groups, according to Blanc's criteria. Comparisons were made on umbilical venous and amniotic fluid PCT levels among the groups. The relations between umbilical venous PCT and IL-6 levels and neonatal and infantile outcomes were also analyzed. RESULTS: The umbilical venous PCT level in the CAM group (240.2 pg/mL, 125.4-350.3 pg/mL: median, first quartile-third quartile) was higher than that in the non-CAM group (105.1, 50.2-137.5 pg/mL; P = 0.0006). There were no differences in the amniotic fluid PCT levels between the groups. There was a strong correlation between umbilical venous PCT and IL-6 levels (correlation coefficient: 0.793). Among 10 cases with an umbilical venous PCT level of ≥170.0 pg/mL and six cases with IL-6 ≥ 11.0 pg/mL, six (60.0%) and five cases (83.3%), respectively, had adverse neonatal and infantile outcomes. Among seven cases with adverse neonatal and infantile outcomes, six (85.7%) and five (71.4%) cases showed umbilical venous PCT levels of ≥170.0 pg/mL and IL-6 levels of ≥11.0 pg/mL, respectively. CONCLUSION: Similar to IL-6, the umbilical venous PCT level is a promising parameter for predicting histological CAM and adverse neonatal and infantile outcomes related to in utero inflammatory status.

BK-UM in patients with recurrent ovarian cancer or peritoneal cancer: a first-in-human phase-I study.

BACKGROUND: BK-UM (CRM197) is a mutant form of diphtheria toxin and a specific inhibitor of heparin-binding epidermal growth factor-like growth factor (HB-EGF). We assessed the safety, pharmacokinetics, recommended dose, and efficacy of BK-UM in patients with recurrent ovarian cancer (OC) or peritoneal cancer (PC), and measured HB-EGF levels in serum and abdominal fluid after BK-UM administration. METHODS: Eleven patients with advanced or recurrent OC or PC were enrolled and treated with BK-UM via the intraperitoneal route. The dose was escalated (1.0, 2.0, 3.3, and 5.0 mg/m2) using a 3 + 3 design. RESULTS: Eight of 11 patients completed treatment. No dose-limiting toxicity (DLT) was experienced at dose levels 1 (1.0 mg/m2) and 2 (2.0 mg/m2). Grade 3 transient hypotension as an adverse event (defined as a DLT in the present study) was observed in two of four patients at dose level 3 (3.3 mg/m2). Treatment with BK-UM was associated with decreases in HB-EGF levels in serum and abdominal fluid in seven of 11 patients and five of eight patients, respectively. Clinical outcomes included a partial response in one patient, stable disease in five patients, and progressive disease in five patients. CONCLUSIONS: BK-UM was well tolerated at doses of 1.0 and 2.0 mg/m2, with evidence for clinical efficacy in patients with recurrent OC or PC. A dose of 2.0 mg/m2 BK-UM is recommended for subsequent clinical trials. TRIAL REGISTRATION: This trial was prospectively performed as an investigator-initiated clinical trial. The trial numbers are UMIN000001002 and UMIN000001001, with registration dates of 1/30/2008 and 2/4/2008, respectively. UMIN000001001 was registered as a trial for the continuous administration of BK-UM after UMIN000001002 .

A survey on awareness of genetic counseling for non-invasive prenatal testing: the first year experience in Japan.

The purpose of this study is to summarize the results from a survey on awareness of genetic counseling for pregnant women who wish to receive non-invasive prenatal testing (NIPT) in Japan. As a component of a clinical study by the Japan NIPT Consortium, genetic counseling was conducted for women who wished to receive NIPT, and a questionnaire concerning both NIPT and genetic counseling was given twice: once after pre-test counseling and again when test results were reported. The responses of 7292 women were analyzed. They expressed high satisfaction with the genetic counseling system of the NIPT Consortium (94%). The number of respondents who indicated that genetic counseling is necessary for NIPT increased over time. Furthermore, they highly valued genetic counseling provided by skilled clinicians, such as clinical geneticists or genetic counselors. The vast majority (90%) responded that there was sufficient opportunity to consider the test ahead of time. Meanwhile, women who received positive test results had a poor opinion and expressed a low-degree satisfaction. We confirmed that the pre-test genetic counseling that we conducted creates an opportunity for pregnant women to sufficiently consider prenatal testing, promotes its understanding and has possibilities to effectively facilitate informed decision making after adequate consideration. A more careful and thorough approach is considered to be necessary for women who received positive test results.

Fetal Hepatic Hemangioma Diagnosed in Utero Using Doppler Microvascular Imaging.

A 35-year-old pregnant woman was referred to our institution at 33 weeks' gestation for evaluation of a fetal abdominal tumor. B-mode ultrasonography demonstrated a massive lesion. Bidirectional power Doppler mode showed abundant blood flow surrounding the tumor. On superb micro-vascular imaging, various Doppler signal patterns were observed within the tumor, including diffuse fine dotted-like signals, linear flow, and internal shunt flow. Sequential observations of the tumor and cardiac cycles also revealed pulsatile flow beneath the edges of the tumor and continuous fine flow in the central area, resembling a 'centripetal fill-in' appearance on contrast computed tomography. Therefore, we assumed the fetal tumor to be a hepatic hemangioma. Fetal heart failure was detected at 37 weeks' gestation, and a 2,484-g female infant was delivered with 1- and 5-min Apgar scores of 7 and 8, respectively. A postnatal contrast computed tomography examination showed a progressive centripetal fill-in appearance, leading to a diagnosis of hepatic hemangioma. Kasabach-Merritt syndrome was also noted. Intensive treatment was performed, and the infant was discharged at 3 months after birth. In summary, we experienced a case of hepatic hemangioma diagnosed in utero using superb micro-vascular imaging. And basing seamless postnatal treatments on prenatal imaging findings may help to reduce the perinatal mortality.

Risk Factors in Fetal Ovarian Cysts for Postnatal Adverse Outcomes.

AIM: To investigate the natural history of fetal ovarian cysts and elucidate the risk factors for postnatal adverse outcomes in fetal ovarian cysts. METHODS: The study subjects were 18 cases with ovarian cysts prenatally diagnosed using ultrasonography at our hospital between 2007 and 2020. The subjects were classified by cyst characteristics according to echogenic patterns [simple cyst (S) and complex cyst (C)], changes in echogenic patterns (S-to-S, S-to-C, and C-to-C), and diameters (<40 and ≥ 40 mm). Clinical parameters and outcomes were compared between S and C patterns, S-to-S and S-to-C patterns, and <40 and ≥ 40 mm diameters. RESULTS: Cases with S and C patterns (15 and 3, respectively) had median gestational ages of 35 and 36 weeks, respectively, and maximum cyst diameters of 36 and 57mm, respectively. The number of cases with S-to-S, S-to-C and C-to-C patterns were 11, 4 and 3, respectively. The maximum cyst diameter in cases with S-to-C patterns (58 mm) was larger than that in cases with S-to-S patterns (34 mm) (P<0.05). Placental weight in cases with cysts >40 mm and/or cyst expansion was greater than that in cases with neither or both conditions (P<0.05). Spontaneous resolution (before and after birth) occurred in 8 of 9 and 3 of 9 cases with maximum cyst diameters <40 and ≥ 40 mm, respectively. Ovarian function was lost in 2 cases with S-to-C patterns and in 2 cases with C-to-C patterns. CONCLUSION: Cases with cyst diameters ≥ 40 mm and/or cyst expansion during the late third trimester had greater placental weight and more postnatal adverse outcomes.

Innovative hemostasis technique for cesarean section in placenta previa: A retrospective study.

OBJECTIVE: To evaluate hemostatic efficacy, complications, and subsequent pregnancy outcomes in women with placenta previa who underwent combined vertical compression sutures in the lower uterine segment and intrauterine balloon tamponade (Hot-Dog method) to achieve hemostasis after cesarean section. METHODS: We retrospectively reviewed data for 117 women with singleton pregnancy diagnosed with placenta previa who underwent cesarean section between 29 and 38 weeks' gestation. Treatments were as follows: (1) conventional-intravenous oxytocin administration after placental detachment and suturing of bleeding points at the detachment site as needed (conventional group) (n = 47). (2) Intrauterine balloon tamponade alone (balloon group) (n = 41). (3) Vertical compression sutures + intrauterine balloon tamponade (Hot-Dog group) (n = 29). RESULTS: The placenta accreta spectrum prevalence was significantly higher in the balloon and Hot-Dog groups versus the conventional group. The prevalence of anteriorly located placenta was significantly higher in the Hot-Dog versus balloon groups. Intraoperative and total blood loss were significantly higher in the Hot-Dog versus conventional groups. Postoperative blood loss was significantly lower in the Hot-Dog versus balloon groups. Fewer additional procedures for managing postoperative hemorrhage were required in the Hot-Dog versus conventional and balloon groups. The number of subsequent pregnancies in the conventional, balloon, and Hot-Dog groups was 11 (23.4%), 8 (19.5%), and 4 (13.8%), respectively; all resulted in live births at term without serious obstetric complications. CONCLUSION: The Hot-Dog method is a straightforward and safe hemostasis technique for placenta previa that preserves fertility and controls severe bleeding.

Risk factors for placenta accreta spectrum in pregnancies conceived after frozen-thawed embryo transfer in a hormone replacement cycle.

OBJECTIVE: Assisted reproductive technology (ART), especially frozen-thawed embryo transfer (FET) in a hormone replacement cycle (HRC), is a risk factor for placenta accreta spectrum (PAS). This study aimed to clarify the risk factors for PAS related to the maternal background and ART techniques in pregnancies achieved after FET in an HRC. STUDY DESIGN: We performed a case-control study in two tertiary perinatal centres in Japan. Among 14,028 patients who delivered at ≥24 weeks of gestation or were transferred after delivery to two tertiary perinatal centres between 2010 and 2021, 972 conceived with ART and 13,056 conceived without ART. PAS was diagnosed on the basis of the FIGO classification for the clinical diagnosis of PAS or retained products of conception after delivery at ≥24 weeks of gestation. We excluded women with fresh embryo transfer, FET with a spontaneous ovulatory cycle, a donor oocyte cycle, and missing details of the ART treatment. Finally, among women who conceived after FET in an HRC, 62 with PAS and 340 without PAS were included in this study. Multivariate logistic regression models were used for case-control comparisons, with adjustment for maternal age at delivery, parity, endometriosis or adenomyosis, the number of previous uterine surgeries of caesarean section, myomectomy, endometrial polypectomy or endometrial curettage, placenta previa, the stage of transferred embryos, and endometrial thickness at the initiation of progestin administration. RESULTS: PAS was associated with ≥2 previous uterine surgeries (adjusted odds ratio, 3.57; 95 % confidence interval, 1.60-7.97) and the stage of embryo transfer (blastocysts: adjusted odds ratio, 2.89; 95 % confidence interval, 1.15-7.26). In patients with <2 previous uterine surgeries, PAS was associated with an endometrial thickness of <7.0 mm (adjusted odds ratio, 5.18; 95 % confidence interval, 1.10-24.44). CONCLUSION: Multiple uterine surgeries and the transfer of blastocysts are risk factors for PAS in pregnancies conceived after FET in an HRC. In women with <2 previous uterine surgeries, a thin endometrium before FET is also a risk factor for PAS in these pregnancies.