Perinatal risk factors associated with severity of haemolytic disease of the foetus and newborn due to Rhc maternal-foetal incompatibility: A retrospective cohort study.

BACKGROUND AND OBJECTIVES: Anti-c is the third red blood cell antibody responsible for haemolytic disease of the foetus and newborn (HDFN) requiring intrauterine transfusion. We aimed to identify risk factors associated with HDFN and severe HDFN due to Rhc maternal-foetal incompatibility. MATERIALS AND METHODS: A retrospective cohort study was conducted in Paris and the surrounding area (France), between 2013 and 2015. We included mothers and their children managed by the National Reference Centre in Perinatal Hemobiology for alloimmunization and maternal-foetal incompatibility for the Rhc antigen (N = 121). We conducted bivariate analyses to assess a relationship between perinatal factors (e.g., titre and concentration of anti-c antibodies, direct antiglobulin test) and HDFN, its severity and duration. RESULTS: The incidence of HDFN was 30% (n = 36), including 11% of severe HDFN (n = 13). Seven percent (n = 9) of neonates received at least one transfusion during the first week and 21% (n = 26) after this period until 3 weeks of life. During pregnancy, a concentration ≥7.5 IU/ml and a titre ≥4 and above were associated with HDFN and severe HDFN (p < 0.05). At birth, the high intensity of the quantitative direct antiglobulin test was associated with HDFN and severe HDFN (p < 0.05). A concentration ≥15 IU/ml is the best factor (area under curve [AUC] = 0.78) in predicting HDFN, followed by a titre ≥8 (AUC = 0.76). CONCLUSION: Anti-c alloimmunization causes neonatal anaemia, which is often belated. Paediatricians have to be aware of these risk factors and organize prolonged monitoring of neonates.

Prenatal exome sequencing in 65 fetuses with abnormality of the corpus callosum: contribution to further diagnostic delineation.

PURPOSE: Abnormality of the corpus callosum (AbnCC) is etiologically a heterogeneous condition and the prognosis in prenatally diagnosed cases is difficult to predict. The purpose of our research was to establish the diagnostic yield using chromosomal microarray (CMA) and exome sequencing (ES) in cases with prenatally diagnosed isolated (iAbnCC) and nonisolated AbnCC (niAbnCC). METHODS: CMA and prenatal trio ES (pES) were done on 65 fetuses with iAbnCC and niAbnCC. Only pathogenic gene variants known to be associated with AbnCC and/or intellectual disability were considered. RESULTS: pES results were available within a median of 21.5 days (9-53 days). A pathogenic single-nucleotide variant (SNV) was identified in 12 cases (18%) and a pathogenic CNV was identified in 3 cases (4.5%). Thus, the genetic etiology was determined in 23% of cases. In all diagnosed cases, the results provided sufficient information regarding the neurodevelopmental prognosis and helped the parents to make an informed decision regarding the outcome of the pregnancy. CONCLUSION: Our results show the significant diagnostic and prognostic contribution of CMA and pES in cases with prenatally diagnosed AbnCC. Further prospective cohort studies with long-term follow-up of the born children will be needed to provide accurate prenatal counseling after a negative pES result.

Managing the Unusual Causes of Fetal Anemia.

BACKGROUND: Rare causes of fetal anemia requiring intrauterine transfusion (IUT) are challenging for fetal medicine specialists. OBJECTIVES: The aim of this study was to describe the perinatal patterns and prognosis in a consecutive series of fetuses transfused for fetal anemia of rare or unknown etiology, and to propose a protocol of investigation for fetal anemia of undetermined cause and for the management of subsequent pregnancies. METHOD: We conducted a retrospective descriptive study on fetuses transfused for severe anemia of rare or unknown etiology managed in our national referral center (Centre National de Référence d'Hémobiologie Périnatale) and born between 2010 and 2017. RESULTS: During the study period, 584 IUT were performed in 253 fetuses. Among those IUT, 23 (3.9%) were performed for a rare or unknown cause of anemia in 13 fetuses (5.1% of transfused fetuses). The median gestational age at diagnosis was 26 weeks of gestation (WG; range 21-33). Hemoglobin levels ranged from 1.6 to 9.1 g/dL (0.18-0.83 multiples of median) before the first IUT. The fetuses received between 1 and 6 IUT (39% received at least 2 IUT). The definitive etiologies for central anemia were: congenital syphilis, neonatal poikilocytosis, type II congenital dyserythropoietic anemia (CDA), and neonatal hemochromatosis. There was 1 case with suspected type I CDA and 1 with suspected Diamond-Blackfan anemia. There was 1 case of peripheral anemia, secondary to cerebral hemorrhages of different ages, related to a variant of the COL4A1 gene. In 6 fetuses corresponding to 4 mothers, no precise diagnosis was found despite a complete workup. In our series, there were 8 live births, 4 terminations of pregnancy, and 1 intrauterine fetal death. CONCLUSIONS: Fetal anemia of rare or unknown diagnosis represents 5% of all transfused fetuses in our cohort. Fetal and neonatal anemias can be recurrent in further pregnancies, with variable expressivity.

Prenatal Imaging Findings of Pontine Tegmental Cap Dysplasia: Report of Four Cases.

OBJECTIVES: To describe the prenatal imaging findings in pontine tegmental cap dysplasia (PTCD), a rare congenital malformation of the hindbrain so far reported postnatally only and characterized by a typical appearance of the pons with malformations of the vermis and the cerebellar peduncles. METHODS: This retrospective multicenter study retrieved 4 cases of PTCD over a 10-year period. Prenatal ultrasonography and fetal magnetic resonance imaging (MRI) findings were reviewed and compared to postnatal or postmortem data. RESULTS: In all cases, the parents were referred between 22 and 27 weeks of gestation for characterization of a small cerebellar diameter <3rd centile. The prenatal diagnosis of PTCD was suspected in 1/4 cases, while in 3/4 cases the suggested prenatal diagnosis was pontocerebellar hypoplasia. In all cases, PTCD was characterized by ventral pontine hypoplasia with absence of bulging of the pons and by the tegmental cap protruding into the fourth ventricle on prenatal MRI. Parents opted for termination of pregnancy in 1 case. In the 3 other cases, the children presented with global developmental delay and multiple cranial nerve impairment. CONCLUSION: PTCD is a differential diagnosis of pontocerebellar hypoplasia and should be discussed on prenatal MRI in the presence of the tegmental cap protruding into the fourth ventricle.

Two-Port Fetoscopic Repair of Myelomeningocele in Fetal Lambs.

OBJECTIVE: The aim of this study was to assess the feasibility and the effectiveness of a fetoscopic myelomeningocele (MMC) repair with a running single suture using a 2-port access in the sheep model. METHODS: Eighteen fetuses underwent surgical creation of a MMC defect at day 75. Fetuses were then randomized into 3 groups. Four fetuses remained untreated (control group). In the other 14 fetuses, a prenatal repair was performed at day 90: 7 fetuses had an open repair (oMMC), and 7 fetuses had a fetoscopic repair (fMMC) using a single-layer running suture through a 2-port access. Lambs were sacrificed at term, and histological examinations were performed. RESULTS: Hindbrain herniation was observed in all live lambs in the control group. A complete closure of the defect was achieved in all the lambs of the fMMC group. A complete healing of the defect and no hindbrain herniation were observed in all live lambs of the oMMC and fMMC groups. The durations of surgeries were not statistically different between the oMMC and the fMMC groups (60 vs. 53 min, p = 0.40), as was the risk of fetal loss (fMMC: 1/7, oMMC: 3/7, p = 0.56). DISCUSSION: Fetoscopic repair of MMC can be performed using a single-layer running suture through a 2-port access and may be promising to reduce the risk of premature rupture of membranes.

Fetal Brain Injury Associated with Parvovirus B19 Congenital Infection Requiring Intrauterine Transfusion.

BACKGROUND: Infection with parvovirus B19 (B19V) during pregnancy may cause severe fetal anemia, hydrops, and fe tal death. Furthermore, neurodevelopmental impairment among survivors may occur despite appropriate prenatal management, including intrauterine transfusion (IUT). OBJECTIVES: Our primary objective was to describe cerebral lesions on MRI in fetuses with severe anemia requiring IUT for B19V infection. Our secondary objective was to search for clinical and biological characteristics associated with the occurrence of such lesions. STUDY DESIGN: We performed a retrospective review of data on fetuses infected with B19V and requiring at least one IUT between 2005 and 2016. Fetuses with abnormal cerebral MRI results in the 3rd trimester were compared to those with normal MRI results. RESULTS: Of 34 transfused fetuses, 26 children were born at full term. Five intrauterine fetal deaths, 1 neonatal death, and 2 terminations of pregnancy occurred. Cerebral anomalies were observed in 7/27 fetuses on MRI, including cerebellar hemorrhage or a small cerebellum. Only viral load in fetal blood appeared to be associated with brain lesions (11.5 log10 copies/mL [10.5-12.5] in case of abnormal MRI results vs. 9.5 log10 copies/mL [7.8-10.0]; p = 0.05). CONCLUSIONS: Among the fetuses transfused for B19V infection, 26% presented with prenatal abnormal cerebral imaging results. In our study, viral load in fetal blood appeared to be the only factor associated with fetal brain lesions.

Clinical input of anti-D quantitation by continuous-flow analysis on autoanalyzer in the management of high-titer anti-D maternal alloimmunization.

BACKGROUND: In addition to titration by indirect antiglobulin test most widely used, anti-D quantitation by continuous-flow analysis (CFA) may be performed to assess severity of maternal immunization. Only five studies have reported its added value in the management of pregnancies complicated by anti-D immunization. STUDY DESIGN AND METHODS: A retrospective study of 74 severe anti-D-immunized pregnancies was conducted from January 1, 2013, to December 31, 2014, in the Trousseau Hospital in Paris (France). Concentration of maternal anti-D was measured by titration and by CFA two-stages method (2SM; total amount of anti-D) and one-stage method (1SM; high-affinity IgG1 anti-D). These biologic data were analyzed according to the severity of the hemolytic disease of the fetus and the newborn. RESULTS: The value of 5 IU anti-D/mL in maternal serum is validated as a threshold to trigger ultrasonographic and Doppler fetal close follow-up. A high 1SM/2SM ratio was associated with a higher risk of intrauterine transfusion (IUT). For pregnancies requiring IUT and without increasing titer, maternal 1SM anti-D concentration tends to correlate with the precocity of fetal anemia. In the "without-IUT" group 1SM and 2SM anti-D concentrations correlate significantly with cord bilirubin levels of the newborn at birth. CONCLUSION: Altogether our results underline the importance of anti-D quantitation by CFA to optimize the management of anti-D-alloimmunized pregnancies.

Patterns of Detection of Fetal Posterior Fossa Anomalies: Analysis of 81 Cases in the Second Half of Gestation.

OBJECTIVE: To establish which characteristics of fetal ultrasound screening lead to the diagnosis of posterior fossa (PF) anomalies. METHODS: A total of 81 fetuses with PF anomalies diagnosed after dedicated neuroimaging between July 1, 2007, and January 1, 2013, were included. The ultrasound characteristics of the fetal cerebellum categorized according to an anatomical approach to the PF, associated fetal anomalies, gestational age at diagnosis, and the potential benefits from systematic measurement of the transverse cerebellar diameter (TCD) were analyzed. RESULTS: Fifty fetuses (61.7%) presented with a PF malformation responsible for an increased "fluid-filled" space of the PF, 24 fetuses (29.6%) had a malformation associated with a decreased cerebellar biometry, 23 fetuses (28.4%) had an abnormal cerebellar anatomy and/or echogenicity, and 2 fetuses (2.4%) showed an isolated malformation of the brainstem. Forty-seven cases (58%) showed additional cerebral or extracerebral anomalies, which led to the diagnosis of PF anomaly in 55.3% of the cases. Isolated PF anomalies were associated with an increased "fluid-filled" space of the PF in 91.2% of the cases. Twenty-eight fetuses had a TCD measurement considered as pathological. DISCUSSION: Examination of the transcerebellar plane during 2nd- and 3rd-trimester ultrasound screening combined with systematic measurement of the TCD would allow improving the detection of PF anomalies.

Fetoscopic patch coverage of experimental myelomenigocele using a two-port access in fetal sheep.

PURPOSE: This study aims to assess the feasibility and the effectiveness of a fetoscopic myelomeningocele (MMC) coverage using a sealed inert patch through a two-port access, in the sheep model. METHODS: Forty-four fetuses underwent surgical creation of a MMC defect at day 75 and were divided into four groups according to the MMC repair technique, performed at day 90. Group 1 remained untreated. Group 2 had an open surgery using suture of the defect. Groups 3 and 4 underwent defect coverage using a Gore®-polytetrafluoroethylene patch secured with surgical adhesive (Bioglue®), with an open approach (group 3) and a fetoscopic one (group 4). Lambs were killed at term, and histological examinations were performed. RESULTS: Fetoscopic patch coverage was achieved in all the lambs of group 4. All the fetuses of group 2 had a complete closure of the defect whereas only 38% in group 3 and 14% in group 4. Fetal loss rate seems to be lower in group 4 than in groups 2 and 3. CONCLUSION: Fetoscopic coverage of MMC defect can be performed using a sealed patch through a two-port access, but the patch and glue correction may not be the ideal technique to repair fetal MMC.

Limited Dorsal Myeloschisis: A Diagnostic Pitfall in the Prenatal Ultrasound of Fetal Dysraphism.

OBJECTIVE: To determine the ultrasonographic characteristics of limited dorsal myeloschisis (LDM) at prenatal ultrasound (US) and to highlight the main features that may help differentiate LDM and myelomeningocele (MMC). METHODS: In a tertiary reference center in fetal medicine, we prospectively collected the medical data and ultrasonographic characteristics of all patients referred for in utero prenatal repair of MMC between November 1, 2013 and April 30, 2015. RESULTS: Among the 29 patients assessed, the diagnosis of MMC was revised in 7 cases. In 6 cases, the diagnosis of LDM was established. On US scan, LDM was characterized by a spinal saccular lesion with a thick peripheral lining in continuity with the adjacent skin. Within the saccular lesion, a thick hyperechoic well-delineated structure was present in continuity with the spinal cord. Cerebral structures were normal except for 2 cases showing a cisterna magna slightly decreased in size. In the remaining 22 cases MMC was confirmed, with cerebral anomalies present in 21/22 cases (95.5%). CONCLUSION: LDM is a form of closed dysraphism accessible to prenatal diagnosis by US that may mimic MMC. Considering the major difference in prognosis between these two entities, physicians should be aware of the existence and ultrasonographic characteristics of LDM.

Prenatal Sacral Anomalies Leading to the Detection of Associated Spinal Cord Malformations.

INTRODUCTION: Systematic analysis of the spine is recommended as part of the basic sonographic examination. The aim of our study is to assess the proportion of spinal cord anomalies diagnosed following detection of a sacral anomaly. MATERIAL AND METHODS: We analyzed retrospectively collected data in a prenatal tertiary center during a 9-year period. Patients were referred for second-line ultrasound in the context of diabetes mellitus or following detection of pelvic or lower spine anomalies. We included all cases of sacral anomalies with available postnatal or postmortem outcomes (imaging and/or pathologic data) and excluded all cases of open dysraphism (myelomeningocele). RESULTS: Nineteen patients were included. The mean gestational age was 28 weeks (21-39). Sacral anomalies included 2 cases of complete agenesis, 12 cases of partial agenesis, 4 segmentation anomalies, and 1 case of abnormal angulation of the sacral spine. Fourteen associated spinal cord malformations included 8 tethered spinal cords, 5 truncated spinal cords, and 1 lipoma of the filum terminale. All anomalies were confirmed by postnatal or postmortem examinations. CONCLUSIONS: Sacral anomalies detected during basic sonographic examination represent an important warning sign for associated spinal cord anomalies, with possible poor neonatal outcome.

Prognosis of Fetal Parenchymal Cerebral Lesions without Ventriculomegaly in Congenital Toxoplasmosis Infection.

OBJECTIVE: To evaluate the neurodevelopmental and ocular outcome of a continuous retrospective series of fetal toxoplasmosis infections for which prenatal ultrasound (US) follow-up revealed abnormal cerebral findings without associated ventriculomegaly. MATERIALS AND METHODS: We retrospectively reviewed all cases of proven fetal Toxoplasma gondii infection with fetal cerebral anomalies at US examination without significant ventriculomegaly (≥10 mm) evaluated in our center over a 5-year period. US and magnetic resonance imaging findings were collected. The neurodevelopmental and ocular outcomes of the cases were studied. RESULTS: Nine fetuses were included. Hyperechogenic foci of the cerebral parenchyma were isolated in five cases. Among those, four children had normal neurological development. Amblyopia was detected in on case. Hyperechogenic foci were associated with other anomalies of cerebral parenchyma in three cases among which two children had normal neurological development. Termination of pregnancy was performed in three cases: one case within the context of severe maternal schizophrenia with isolated hyperechogenic foci, one case where hyperechogenic foci were associated with extensive lesions of the white matter, and one case for severe fetal hydrops. CONCLUSION: The neurological prognosis of cerebral hyperechogenic lesions without ventriculomegaly in fetal toxoplasmosis infection may be favorable. The risk of ocular damage however remains high and unpredictable in the prenatal period.

Accuracy of Middle Cerebral Artery Doppler Assessment between 34 and 37 Weeks in Fetuses with Red Cell Alloimmunization.

BACKGROUND: The Doppler measurement of middle cerebral artery peak systolic velocity (MCA-PSV) is considered the gold standard for the noninvasive detection of moderate to severe anemia. However, the accuracy of this test has not been evaluated so far, specifically beyond 34 weeks. OBJECTIVES: To assess the accuracy of MCA-PSV to detect moderate to severe fetal anemia and to identify risk factors associated with false-positive and false-negative MCA-PSV values after 34 weeks. STUDY DESIGN: We studied a retrospective cohort of 150 pregnant women with severe alloimmunization who delivered between 2010 and 2014 and correlated MCA-PSV and fetal or neonatal hemoglobin levels. RESULTS: Sensitivity to predict severe anemia was 69%, with a false-negative rate of 3.6%. When MCA Doppler assessment was normal, the identification of serosal effusions increased the detection rate of severe fetal anemia to 94%, with a false-negative rate of 0.8%. False-positive MCA-PSV measurements were more frequent in fetuses with 1 previous intrauterine transfusion (p = 0.0002), but were not associated with MCA resistance index, intrauterine growth restriction and fetal heart rate. CONCLUSIONS: Between 34 and 37 weeks, sensitivity of MCA-PSV Doppler assessment alone is 69% and increases to 94% when also considering signs of hydrops. False-positive MCA-PSV measurements are more frequent in case of former fetal transfusion.

Analysis of MRI brain biometrics in fetuses monitored for intra uterine growth restriction and their prognostic value: Results of a prospective multicenter study.

OBJECTIVE: Show a prognostic value of brain changes in fetuses with intra uterine growth restriction (IUGR) on early neonatal outcome. STUDY DESIGN: We prospectively recruited pregnant women whose fetuses presented fetal weight < 5th centile. A brain MRI was performed between 28 and 32 weeks of gestation (WG). Several brain biometrics were measured (as fronto-occipital diameter (FOD) and transverse cerebellar diameter (TCD)). Neonatal prognosis was evaluated according to a composite criterion. RESULTS: Of the 78 patients included, 62 had a fetal brain MRI. The mean centile value of FOD was lower in the unfavorable outcome group (n = 9) compared to the favorable outcome group (n = 53) (24.5 ± 16.8 vs. 8.6 ± 13.2, p = 0.004). The ROC curve for predicting risk of unfavorable neonatal outcome based on FOD presented an area under the curve of 0.81 (95 % CI, [0.63---0.99]) and a threshold determined at the 3rd centile was associated with sensitivity of 0.78 and a specificity of 0.89. In multivariate analysis, a FOD less than the 3rd centile was significantly associated with an unfavorable neonatal risk. There also was a reduction in TCD (25.5 ± 21.5 vs. 10.4 ± 10.4, p = 0.03) in the unfavorable neonatal outcome group. CONCLUSION: We found an association between a reduction in FOD and TCD in fetal MRIs conducted between 28 and 32 WG in fetuses monitored for IUGR with an unfavorable neonatal outcome. Our results suggest that these biometric changes could constitute markers of poor neonatal prognosis.

Effect of intravenous immunoglobulins to postpone the gestational age of first intrauterine transfusion in very severe red blood cell alloimmunization: A case-control study.

BACKGROUND: Early intrauterine transfusion (IUT) is associated with a higher risk of fetal loss. Our objective was to evaluate the efficiciency of intravenous immunoglobulins (IVIG) to postpone the gestational age at first IUT beyond 20 weeks of gestation (WG) compared to the previous pregnancy in case of very severe red blood cell (RBC) alloimmunization. STUDY DESIGN AND METHODS: Very severe RBC alloimmunization was defined by a high titer of antibodies and a previous pregnancy complicated by a first IUT before 24 WG and/or perinatal death directly related to alloimmunization. We performed a single-center case-control study. Cases and controls were patients respectively treated with weekly IVIG infusions started before 13 WG, and without. RESULTS: Twenty cases and 21 controls were included. Gestational age (GA) at first IUT was postponed after 20 WG in 18/20 (90 %) of patients treated with IVIG and in 15/21 (71 %) in the control group (p = 0.24). Compared to the previous pregnancy, the GA at first IUT was postponed by a median of 22 [+11; +49] days in the IVIG group and occurred in average 2 days earlier [-17 ; +12] in the non-treated group (p = 0.02). There was no difference between number of IUT and need for exchange-transfusion. IVIG treatment was associated with a significant decrease of antibodies' quantitation. CONCLUSION: In our series, IVIG tends to differ first IUT beyond 20 WG and have a significant effect in postponing the gestational age of the first IUT in patients with very severe RBC alloimmunization.

Open fetal surgery for myelomeningocele repair in France.

INTRODUCTION: Open fetal myelomeningocele (MMC) surgery is currently the standard of care option for prenatal MMC repair. We described the population referred to our center and reviewed outcome after open fetal MMC repair. MATERIAL AND METHODS: All patients referred to our center for MMC were reviewed from July 2014 to June 2020. For all the patients who underwent fetal MMC repair, surgical details, maternal characteristics and data from the neonatal to the three-years-old evaluations were collected. RESULTS: Among the 126 patients referred to our center, 49.2% were eligible and 27.4% (n = 17) of them underwent fetal MMC repair. Average gestational age at fetal surgery was 24+6 weeks. There was no case of fetal complication and the only maternal complication was one case of transfusion. We recorded 70% of premature rupture of membranes and 47% of premature labor. Average gestational age at delivery was 34+2 weeks and no patient delivered before 30 weeks. There was no case of uterine scar dehiscence or maternal complication during cesarean section. After birth, 59% of the children had a hindbrain herniation reversal. At 1-year-old, 42% were assigned a functional level of one or more better than expected according to the prenatal anatomic level and 25% required a ventriculoperitoneal shunt. At 3-year-old, all the children attended school and 75% were able to walk with orthotics or independently. CONCLUSION: Open fetal surgery enables anatomical repair of the MMC lesion, a potential benefit on cerebral anomalies and motor function, with a low rate of perinatal and maternal complications.

Pregnancy outcome after first trimester exposure to ionizing radiations.

OBJECTIVE: To evaluate the effects of ionizing radiation exposure during the first trimester of pregnancy in usual clinical situations. STUDY DESIGN: We conducted a prospective observational cohort study using data collected between 1987 and 2014. This database was authorized by the French "Commission Nationale de l'Informatique et des Libertés". The exposed group consisted of 319 pregnant women exposed to sub diaphragmatic ionizing radiations for diagnostic purposes, during the first trimester of pregnancy, and the control group consisted of 319 pregnant women without any exposure or exposed to non-teratogenic agents. Data on maternal history and radiations exposure were collected on first contact, and pregnancy outcomes were documented at follow-up. An univariate analysis was performed to compare both groups for the main outcomes. RESULTS: Exposure to sub diaphragmatic ionizing radiation for diagnosis purpose (median fetal dose of 3.1 mGy [0.2-130.0]) during the first trimester of pregnancy was not significantly associated with an increased risk of malformations (1.5% vs 1.8%, p = 1.00), miscarriage (7.8% vs 7.2%, p = 0.88), in utero fetal death (0.3% vs 0%, p = 1.00) or fetal growth restriction (5.4% vs 3.5%, p = 0.62). CONCLUSION: Pregnant women exposed to irradiant diagnostic procedures do not present a higher risk of malformations, miscarriage, in utero fetal death or fetal growth restriction and should be reassured, even if the examination focused on the pelvis.

Developing a knowledge base to support the annotation of ultrasound images of ectopic pregnancy.

BACKGROUND: Ectopic pregnancy is a frequent early complication of pregnancy associated with significant rates of morbidly and mortality. The positive diagnosis of this condition is established through transvaginal ultrasound scanning. The timing of diagnosis depends on the operator expertise in identifying the signs of ectopic pregnancy, which varies dramatically among medical staff with heterogeneous training. Developing decision support systems in this context is expected to improve the identification of these signs and subsequently improve the quality of care. In this article, we present a new knowledge base for ectopic pregnancy, and we demonstrate its use on the annotation of clinical images. RESULTS: The knowledge base is supported by an application ontology, which provides the taxonomy, the vocabulary and definitions for 24 types and 81 signs of ectopic pregnancy, 484 anatomical structures and 32 technical elements for image acquisition. The knowledge base provides a sign-centric model of the domain, with the relations of signs to ectopic pregnancy types, anatomical structures and the technical elements. The evaluation of the ontology and knowledge base demonstrated a positive feedback from a panel of 17 medical users. Leveraging these semantic resources, we developed an application for the annotation of ultrasound images. Using this application, 6 operators achieved a precision of 0.83 for the identification of signs in 208 ultrasound images corresponding to 35 clinical cases of ectopic pregnancy. CONCLUSIONS: We developed a new ectopic pregnancy knowledge base for the annotation of ultrasound images. The use of this knowledge base for the annotation of ultrasound images of ectopic pregnancy showed promising results from the perspective of clinical decision support system development. Other gynecological disorders and fetal anomalies may benefit from our approach.