International Society for Prenatal Diagnosis Updated Position Statement on the use of genome-wide sequencing for prenatal diagnosis.

The research and clinical use of genome-wide sequencing for prenatal diagnosis of fetuses at risk for genetic disorders have rapidly increased in recent years. Current data indicate that the diagnostic rate is comparable and for certain indications higher than that of standard testing by karyotype and chromosomal microarray. Responsible clinical implementation and diagnostic use of prenatal sequencing depends on standardized laboratory practices and detailed pre-test and post-test counseling. This Updated Position Statement on behalf of the International Society for Prenatal Diagnosis recommends best practices for the clinical use of prenatal exome and genome sequencing from an international perspective. We include several new points for consideration by researchers and clinical service and laboratory providers.

Hemodynamic and anatomic changes after fetal aortic valvuloplasty are associated with procedural success and postnatal biventricular circulation.

BACKGROUND: There are minimal data characterizing the trajectory of left heart growth and hemodynamics following fetal aortic valvuloplasty (FAV). METHODS: This retrospective study included patients who underwent FAV between 2000 and 2019, with echocardiograms performed pre-FAV, immediately post-FAV, and in late gestation. RESULTS: Of 118 fetuses undergoing FAV, 106 (90%) underwent technically successful FAV, of which 55 (52%) had biventricular circulation. Technically successful FAV was associated with improved aortic valve growth (p < 0.001), sustained antegrade aortic arch (AoA) flow (p = 0.02), improved mitral valve (MV) inflow pattern (p = 0.002), and favorable patent foramen ovale (PFO) flow pattern (p = 0.004) from pre-FAV to late gestation. Compared to patients with univentricular outcome, patients with biventricular outcome had less decrement in size of the left ventricle (LV) (p < 0.001) and aortic valve (p = 0.005), as well as more physiologic PFO flow (p < 0.001) and antegrade AoA flow (p < 0.001) from pre-FAV to late gestation. In multivariable analysis, echocardiographic predictors of biventricular outcome were less decline in LV end diastolic dimension (p < 0.001), improved PFO flow (p = 0.004), and sustained antegrade AoA flow (p = 0.002) from pre-FAV to late gestation. CONCLUSION: Stabilization of left heart growth and improved hemodynamics following successful FAV through late gestation are associated with postnatal biventricular circulation.

Late gestation predictors of a postnatal biventricular circulation after fetal aortic valvuloplasty.

OBJECTIVES: Fetal aortic valvuloplasty (FAV) for severe aortic stenosis (AS) has shown promise in averting progression to hypoplastic left heart syndrome. After FAV, predicting which fetuses will achieve a biventricular (BiV) circulation after birth remains challenging. Identifying predictors of postnatal circulation on late gestation echocardiography will improve parental counseling. METHODS: Liveborn patients who underwent FAV and had late gestation echocardiography available were included (2000-2017, n = 96). Multivariable logistic regression and classification and regression tree analysis were utilized to identify independent predictors of BiV circulation. RESULTS: Among 96 fetuses, 50 (52.1%) had BiV circulation at the time of neonatal discharge. In multivariable analysis, independent predictors of biventricular circulation included left ventricular (LV) long axis z-score (OR 3.2, 95% CI 1.8-5.7, p < 0.001), LV ejection fraction (OR 1.3, 95% CI 1.0-1.8, p = 0.023), anterograde aortic arch flow (OR 5.0, 95% CI 1.2-20.4, p = 0.024), and bidirectional or right-to-left foramen ovale flow (OR 4.6, 95% CI 1.4-15.8, p = 0.015). CONCLUSION: Several anatomic and physiologic parameters in late gestation were found to be independent predictors of BiV circulation after FAV. Identifying these predictors adds to our understanding of LV growth and hemodynamics after FAV and may improve parental counseling.

General practitioners' knowledge about pregnancy complications associated with long-term cardiovascular risk.

INTRODUCTION: Cardiovascular disease (CVD) is the leading cause of mortality in women; preeclampsia (PE) and gestational diabetes mellitus (GDM) are associated with an increased risk of CVD. OBJECTIVE: To evaluate general practitioners (GP) knowledge about complicated pregnancies and their association with CVD. METHODS: An anonymous case-based electronic questionnaire designed to assess the level of understanding on the influence of a history of pregnancy complications on long-term cardiovascular risk and general knowledge about CVD risk was sent to GPs. RESULTS: The response rate was 35 % (161/465). The participants recognized that PE and GDM are risk factors for CVD (98 and 83 %, respectively), and reported the following CVD screening strategies in women with a history of PE and GDM: blood pressure monitoring (PE 100 %, GDM 46 %), body mass index calculation (PE 68 %, GDM 57 %), lipid profile evaluation (PE 71 %, GDM 57 %), glycated hemoglobin (PE 26 %, GDM 92 %), and fasting glucose (PE 28 %, GDM 91 %). CONCLUSION: GP-reported screening strategies to identify CVD in women with a history of PE and GDM were variable.

INTRODUCCIÓN: La enfermedad cardiovascular (ECV) constituye la principal causa de mortalidad en mujeres; la preeclampsia (PE) y la diabetes mellitus gestacional (DMG) están asociadas a incremento en el riesgo de ECV. OBJETIVO: Evaluar el conocimiento de los médicos generales (MG) sobre complicaciones obstétricas asociadas a ECV. MÉTODOS: Se envió a los MG un cuestionario electrónico anónimo basado en casos, diseñado para evaluar el entendimiento de la influencia de la historia obstétrica en el riesgo cardiovascular a largo plazo y el conocimiento general sobre riesgo de ECV. RESULTADOS: La tasa de respuesta fue de 35 % (161/465). Los participantes reconocieron que la PE y la DMG son factores de riesgo para ECV (98 y 83 %, respectivamente) y reportaron las siguientes estrategias de tamizaje de ECV en mujeres con historial de PE y DMG: monitoreo de presión arterial (PE 100 %, DMG 46 %), cálculo de índice de masa corporal (PE 68 %, DMG 57 %), evaluación del perfil de lípidos (PE 71 %, DMG 57 %), hemoglobina glucosilada (PE 26 %, DMG 92 %) y glucosa en ayuno (PE 28 %, DMG 91 %). CONCLUSIÓN: Las estrategias de tamizaje para identificar ECV en mujeres con antecedentes de PE y DMG reportadas por los MG fueron variables.

Fetal cardiac intervention-Perspectives from a single center.

Fetal cardiac intervention was first proposed in the early 1990s to impact cardiac development and survival of fetuses with fetal aortic stenosis and evolving hypoplastic left heart syndrome (HLHS). Although initial attempts of fetal aortic valvuloplasty were unsuccessful and carried a high rate of morbidity and mortality, our collaborative group at the Brigham and Women's Hospital and Boston Children's Hospital have reinvigorated the procedure using improvements in imaging, anesthesia, balloon catheters, and surgical techniques. Two decades of experience have now allowed us to document the safety of in utero intervention and to achieve a better understanding of the impact of midgestation intervention on developing HLHS. Research into underlying genetics, predictive biomarkers, and ways to incorporate stem cell technology will hopefully allow us to further refine the procedure to most benefit children with this historically lethal disease.

Structural Chromosomal Rearrangements Require Nucleotide-Level Resolution: Lessons from Next-Generation Sequencing in Prenatal Diagnosis.

In this exciting era of "next-gen cytogenetics," integrating genomic sequencing into the prenatal diagnostic setting is possible within an actionable time frame and can provide precise delineation of balanced chromosomal rearrangements at the nucleotide level. Given the increased risk of congenital abnormalities in newborns with de novo balanced chromosomal rearrangements, comprehensive interpretation of breakpoints could substantially improve prediction of phenotypic outcomes and support perinatal medical care. Herein, we present and evaluate sequencing results of balanced chromosomal rearrangements in ten prenatal subjects with respect to the location of regulatory chromatin domains (topologically associated domains [TADs]). The genomic material from all subjects was interpreted to be "normal" by microarray analyses, and their rearrangements would not have been detected by cell-free DNA (cfDNA) screening. The findings of our systematic approach correlate with phenotypes of both pregnancies with untoward outcomes (5/10) and with healthy newborns (3/10). Two pregnancies, one with a chromosomal aberration predicted to be of unknown clinical significance and another one predicted to be likely benign, were terminated prior to phenotype-genotype correlation (2/10). We demonstrate that the clinical interpretation of structural rearrangements should not be limited to interruption, deletion, or duplication of specific genes and should also incorporate regulatory domains of the human genome with critical ramifications for the control of gene expression. As detailed in this study, our molecular approach to both detecting and interpreting the breakpoints of structural rearrangements yields unparalleled information in comparison to other commonly used first-tier diagnostic methods, such as non-invasive cfDNA screening and microarray analysis, to provide improved genetic counseling for phenotypic outcome in the prenatal setting.

Fetal phenotypes emerge as genetic technologies become robust.

Prenatal genomic evaluation of the fetus is available at decreasing cost and with a faster turnaround time. However, fetal genotype-phenotype correlations are in their infancy. By comparison, pediatric and adult genotype-phenotype databases are well established and publicly accessible. A similar system for fetal genomics is lacking. When a fetal anomaly is identified by ultrasound imaging, a genetic diagnosis provides important information. However, fetal prognostic counseling is problematic if the only available information is based on outcomes following postnatal diagnoses. The same conditions identified prenatally may have more benign or more deleterious outcomes. Also, the condition may evolve over the pregnancy itself. As genomic testing increasingly examines fetal DNA at a single nucleotide level, the concomitant in utero phenotype deserves equal attention. Often, the reports of fetal phenotype are limited. Among sonologists, an increased awareness of attaining and communicating detailed fetal phenotypes is needed. The interpretation of expanded prenatal sequencing is reliant on deeper fetal phenotyping. The information gained significantly impacts clinical care and understanding of fetal development. This case series highlights: the broad spectrum of fetal phenotypes for known genetic conditions, phenotype progression during pregnancy, and the need to supplement systematic imaging with descriptive details when assessing fetuses with malformations.

Caring for Women After Hypertensive Pregnancies and Beyond: Implementation and Integration of a Postpartum Transition Clinic.

Purpose We developed a postpartum transition clinic to better support women after hypertensive pregnancy. Description Our program goals were (1) early postpartum hypertension medical management, (2) patient and provider education around CVD risk, (3) transition to primary care provider (PCP) and (4) a sustainable clinical model reimbursed by private and public insurances. We focused on women immediately postpartum in this analysis. Assessment Over the course of 5 years, a racially and socioeconomically diverse population of 412 immediately postpartum women received care for one, two or more appointments. Referral diagnoses included antepartum preeclampsia (PET) 51% (210/412), postpartum preeclampsia/hypertension (PP-PET) 22.3% (92/412), preeclampsia superimposed on chronic hypertension (siPET) 10.2% (42/412), chronic hypertension (cHTN) 8.8% (37/412), and gestational hypertension (gHTN) 7.8% (31/412). Almost half of women had 2-3 visits 47.3% (195/412) with no difference by diagnosis (p = 0.18). No show rates were consistently around 25%. Acquisition of home blood pressure monitors increased from 56.8% (44/94) to 93.8% (61/65) over the 5 years (p < 0.0001). Nearly half of patients seen had antihypertensive medication adjustments 48.3% (199/412). Of those patients scheduled, 86.8% (79/91) attended a nutrition consultation. For patients with PCPs within our system, 79.5% (105/132) kept their scheduled follow up PCP appointments. Conclusion We report a postpartum transition clinic after hypertensive pregnancy. In this diverse population, patients attended 2-3 visits, incorporated home blood pressure monitoring, adjusted antihypertensive medications and initiated prevention measures such as nutrition referrals and PCP follow-up. An internist salary was sustained through billings and collections from private and public insurance.

Myocardial injury in fetal aortic stenosis: Insights from amniotic fluid analysis.

OBJECTIVE: Fetal aortic stenosis (AS) imposes pressure load on the developing left ventricle (LV) and leads to derangements in myocardial structure and function via mechanisms that are not well characterized. METHODS: We compared amniotic fluid NT-BNP and troponin levels in fetuses with AS prior to fetal valvuloplasty and controls. We estimated correlations between NT-BNP and fetal echo parameters and identify NT-BNP cutoff associated with biventricular outcome RESULTS: Median NT-BNP level was higher in fetal AS than controls (3858 vs 1737 pg/mL, P < 0.012). By contrast, troponin levels were lower in fetal AS, with troponin > detectable in 0/25 (0%) AS cases compared with 22/85 (26%) controls (P = 0.03). Of 25 fetal AS cases, 12 (48%) had biventricular outcome. Fetuses with NT-BNP < 910 pg/mL were more likely to have biventricular (OR =10) compared with those ≥910 pg/mL (P = 0.045). Higher NT-BNP correlated with earlier gestational age and measures of larger left heart size. CONCLUSION: NT-BNP is elevated in fetal AS, suggesting that LV pressure load and increased wall stress lead to maladaptive stretch-related myocardial remodeling. Troponin is normal in mid-gestation fetal AS, suggesting that ischemia is not the primary factor in fetal response to LV pressure load.

Early hemodynamic changes after fetal aortic stenosis valvuloplasty predict biventricular circulation at birth.

OBJECTIVE: To describe the early hemodynamic changes after fetal aortic valvuloplasty (FAV) for evolving hypoplastic left heart syndrome due to mid-gestational aortic stenosis and to assess whether these early changes predict biventricular (BiV) circulation at neonatal discharge. METHOD: We retrospectively reviewed all technically successful FAV cases resulting in live birth between 2000 and 2015 (n = 93, 45% BiV circulation at neonatal discharge). Paired testing methods were used to compare pre-intervention and post-intervention measures of left ventricular hemodynamics. Logistic regression was used to determine whether these changes were predictive of post-natal outcome. RESULTS: Measures of left heart physiology were markedly abnormal pre-FAV and improved significantly post-FAV. No subjects had systolic antegrade transverse aortic arch flow pre-FAV and 65% of subjects had antegrade flow post-FAV. The number of subjects with abnormal left-to-right patent foramen ovale flow decreased, and the number with biphasic mitral valve inflow increased. The median left ventricular ejection fraction improved after intervention. Amongst the pre-post changes, gaining partially or exclusively antegrade systolic arch flow was the most significant independent predictor of BiV circulation (OR 9.80 and 19.83, respectively, both P < 0.001). CONCLUSION: Technically successful FAV is associated with immediate improvements in left heart physiology that are predictive of BiV circulation at neonatal discharge.

Have we done our last amniocentesis? Updates on cell-free DNA for Down syndrome screening.

Prenatal aneuploidy screening changed significantly in 2012 when cell-free fetal deoxyribonucleic acid (DNA) was introduced as a noninvasive prenatal test. A noninvasive prenatal test detects cell free fragments of fetal DNA from the placenta circulating in maternal blood that coexist with cell-free DNA (cfDNA) of maternal origin. Using next-generation sequencing, the noninvasive prenatal test compares maternal and fetal cfDNA ratios for chromosomes of interest (i.e., 21, 18, 13, X, and Y) to assess chromosomal aneuploidy. Compared to traditional screening using ultrasound and serum markers, the noninvasive prenatal test has superior test characteristics, including a higher detection rate and positive predictive value, and a lower false-positive rate. The noninvasive prenatal test is already used for primary screening in high-risk women and is rapidly expanding to all women. Given its increasing use, understanding the noninvasive prenatal test's limitations is critical. Discordant results (i.e. noninvasive prenatal test is positive for aneuploidy with a normal fetal karyotype) can occur because of biological processes such as aneuploidy confined to the placenta, a vanished twin, maternal aneuploidy or maternal cancer. Use of the noninvasive prenatal test for screening beyond the most common aneuploidies is not recommended. The noninvasive prenatal test is a major advance in prenatal aneuploidy screening but it is not diagnostic and does not replace invasive testing (i.e. chorionic villous sampling or amniocentesis) for confirmation of fetal chromosomal disorders.

Antepartum management and obstetric outcomes among pregnancies with Down syndrome from diagnosis to delivery.

OBJECTIVE: Little is known about the obstetric care of an ongoing pregnancy with trisomy 21. We sought to ascertain an obstetric profile for pregnancies with Down syndrome to help guide prenatal management. METHOD: Pregnancies managed for delivery with trisomy 21 between 2003 and 2014 were analyzed. We reviewed demographic data, diagnostic testing, prenatal surveillance, obstetric outcomes, and placental pathology. T-test, chi-squared test, and Fisher correction were used as indicated. RESULTS: Sixty-eight pregnancies were identified, and four women (5.9%) experienced a loss during the pregnancy. Among the remaining 64 pregnancies, the average gestational age at delivery was 36.9 weeks, growth restriction was present in 12 (17.5%), and major anomalies were present in 51 (75.0%). Delivery was undertaken for non-reassuring fetal surveillance in 35.9% of the pregnancies; 93% of which represented a change from prior reassuring surveillance and 52.6% of which demonstrated histopathologic evidence of placental insufficiency. None among increased maternal age, the presence of an anomaly, or growth restriction were significantly more common in the group with non-reassuring surveillance. CONCLUSION: There are high rates of fetal growth restriction, delivery for non-reassuring fetal status, and evidence of placental insufficiency among affected pregnancies, suggesting a role for antepartum surveillance. © 2017 John Wiley & Sons, Ltd.

Fetal aortic valvuloplasty for evolving hypoplastic left heart syndrome: postnatal outcomes of the first 100 patients.

BACKGROUND: Fetal aortic valvuloplasty can be performed for severe midgestation aortic stenosis in an attempt to prevent progression to hypoplastic left heart syndrome (HLHS). A subset of patients has achieved a biventricular (BV) circulation after fetal aortic valvuloplasty. The postnatal outcomes and survival of the BV patients, in comparison with those managed as HLHS, have not been reported. METHODS AND RESULTS: We included 100 patients who underwent fetal aortic valvuloplasty for severe midgestation aortic stenosis with evolving HLHS from March 2000 to January 2013. Patients were categorized based on postnatal management as BV or HLHS. Clinical records were reviewed. Eighty-eight fetuses were live-born, and 38 had a BV circulation (31 from birth, 7 converted after initial univentricular palliation). Left-sided structures, namely aortic and mitral valve sizes and left ventricular volume, were significantly larger in the BV group at the time of birth (P<0.01). After a median follow-up of 5.4 years, freedom from cardiac death among all BV patients was 96±4% at 5 years and 84±12% at 10 years, which was better than HLHS patients (log-rank P=0.04). There was no cardiac mortality in patients with a BV circulation from birth. All but 1 of the BV patients required postnatal intervention; 42% underwent aortic or mitral valve replacement. On the most recent echocardiogram, the median left ventricular end-diastolic volume z score was +1.7 (range, -1.3 to +8.2), and 80% had normal ejection fraction. CONCLUSIONS: Short- and intermediate-term survival among patients who underwent fetal aortic valvuloplasty and achieved a BV circulation postnatally is encouraging. However, morbidity still exists, and ongoing assessment is warranted.

Clinical diagnosis by whole-genome sequencing of a prenatal sample.

Conventional cytogenetic testing offers low-resolution detection of balanced karyotypic abnormalities but cannot provide the precise, gene-level knowledge required to predict outcomes. The use of high-resolution whole-genome deep sequencing is currently impractical for the purpose of routine clinical care. We show here that whole-genome "jumping libraries" can offer an immediately applicable, nucleotide-level complement to conventional genetic diagnostics within a time frame that allows for clinical action. We performed large-insert sequencing of DNA extracted from amniotic-fluid cells with a balanced de novo translocation. The amniotic-fluid sample was from a patient in the third trimester of pregnancy who underwent amniocentesis because of severe polyhydramnios after multiple fetal anomalies had been detected on ultrasonography. Using a 13-day sequence and analysis pipeline, we discovered direct disruption of CHD7, a causal locus in the CHARGE syndrome (coloboma of the eye, heart anomaly, atresia of the choanae, retardation, and genital and ear anomalies). Clinical findings at birth were consistent with the CHARGE syndrome, a diagnosis that could not have been reliably inferred from the cytogenetic breakpoint. This case study illustrates the potential power of customized whole-genome jumping libraries when used to augment prenatal karyotyping.

Angiogenic markers in pregnancies conceived through in vitro fertilization.

OBJECTIVE: Pregnancies that have been conceived through in vitro fertilization (IVF) have been associated with higher rates of preeclampsia and other complications that are associated with placental dysfunction. We evaluated whether IVF pregnancies, when compared with those conceived spontaneously, would be associated with alterations in serum angiogenic markers. STUDY DESIGN: This was a retrospective cohort study from 3 US academic institutions (2006-2008). Women with singleton pregnancies who conceived via IVF or spontaneously were included. Placental growth factor (PlGF) and soluble fms-like tyrosine kinase-1 (sFlt-1) were measured at 4 time points throughout gestation. Pregnancy outcomes that included diagnosis of preeclampsia or other obstetric complications were ascertained from the medical record. The relationship among IVF status, PlGF, and sFlt-1 were modeled over gestation and stratified by clinical pregnancy outcome. RESULTS: Of the included 2392 singleton pregnancies, 4.5% (108 pregnancies) were conceived though IVF. IVF pregnancies were significantly more likely to be complicated by preeclampsia (15.7% vs 7.7%). IVF pregnancies had significantly higher levels of sFlt-1 at 18, 26, and 35 weeks of gestation (P = .04, P = .004, P < .0001, respectively) and lower levels of PlGF at 18 and 35 weeks of gestation (P = .007 and .0006, respectively). These differences persisted even after being controlled for maternal comorbidities or obstetric outcomes such as preeclampsia. CONCLUSION: Pregnancies conceived via IVF were found to have an increased antiangiogenic profile (elevated sFlt-1 and decreased PlGF) at multiple time points throughout gestation when compared with spontaneously conceived pregnancies. Alterations in the angiogenic profile persisted even after we controlled for maternal comorbidities of clinically evident disorders of abnormal placentation such as preeclampsia. The increased antiangiogenic profile suggests fundamentally aberrant placentation related to in vitro fertilization, which may warrant closer fetal surveillance in these pregnancies.

The association of body mass index with serum angiogenic markers in normal and abnormal pregnancies.

OBJECTIVE: Because obesity is a risk factor for placental dysfunction, we hypothesized that maternal body mass index (BMI) would be associated with alterations in serum angiogenic markers. STUDY DESIGN: We included 2399 singleton pregnancies with and without placental dysfunction in a prospective longitudinal cohort study of angiogenic markers. We modeled the relationship between categorical and continuous BMI, soluble fms-like tyrosine kinase-1 (sFlt-1), and placental growth factor (PlGF) over gestation, stratified by pregnancy outcome. RESULTS: In women with normal pregnancies, a higher BMI was associated with lower sFlt-1 values across gestation (P < .0001), lower PlGF in the second and third trimesters (P < .0001), and lower rate of change in PlGF (P < .0001). Similar relationships were seen between maternal BMI, sFlt-1 (P < .0001), and PlGF (P = .0005) in women with clinically evident placental dysfunction. CONCLUSION: The sFlt-1 value is inversely associated with maternal BMI. The pattern of change in PlGF is also dependent on maternal BMI, indicating that obese women may have abnormalities in angiogenesis near term.

Percutaneous fetal cardiac interventions for structural heart disease.

INTRODUCTION: Prenatal diagnosis provides valuable information regarding a variety of congenital heart defects. Some defects occur early in gestation with little change throughout pregnancy, whereas others evolve during mid and late gestation. Fetal cardiac intervention (FCI) affords the opportunity to interrupt progression of disease in this latter category, resulting in improved perinatal and lifelong outcomes. AIM: This chapter addresses three lesions for which percutaneous FCI can be utilized: (1) aortic stenosis with evolving hypoplastic left heart syndrome, for which aortic valvuloplasty may prevent left ventricular hypoplasia and has yielded a biventricular circulation in approximately one third of cases; (2) hypoplastic left heart syndrome with intact atrial septum, for which relief of atrial restriction has potential to improve perinatal survival; and (3) pulmonary atresia with intact ventricular septum and evolving right ventricular hypoplasia, for which pulmonary valvuloplasty has resulted in a biventricular circulation in the majority of patients. The pathophysiology, rationale for intervention, patient selection criteria, procedural technique, and outcomes for each lesion will be reviewed. This chapter will also review complications of FCI and their treatment, and maternal and fetal anesthesia specific to FCI. The importance of a specialized center with experience managing infants delivered after FCI will also be addressed.

Technical Success and Serious Adverse Events for Fetal Aortic Valvuloplasty in a Large 20-Year Cohort.

Background: FAV is offered to fetuses with severe aortic valve stenosis and evolving hypoplastic left heart syndrome. An inferential analysis of TS and SAE in a large series has not been reported. Objectives: The purpose of this study was to determine factors associated with fetal aortic valvuloplasty (FAV) technical success (TS) and serious adverse events (SAEs). Methods: Retrospective, single-center, cohort analysis of attempted FAV from March 1, 2000, to December 31, 2020. The primary outcome was the TS of FAV, and the secondary outcome was the presence of an SAE. Results: A total of 165 FAVs were attempted in 163 patients with a median gestational age of 24.6 weeks (IQR: 22.9-27.1 weeks). FAV TS was 85% (141/165) and was higher in the 2010 to 2020 era (94% [85/90] vs 75% [56/75]; P < 0.001). Pre-FAV echocardiographic left ventricle (LV) long axis dimension z-score >-0.10 (P < 0.001) and higher LV ejection fraction (P = 0.037) were independently associated with a higher odds of TS. There were 117 SAEs in 67 attempted FAVs (41%), 13 of which were fetal deaths (7.9%). By classification and regression tree analysis, gestational age <21 weeks or in older fetuses, a procedure time of ≥39.6 minutes was associated with higher SAE rate. In the multivariable logistic regression model correcting for gestational age, fetuses with an LV end-diastolic volume <4.09 mL had an age-adjusted OR of 4.71 (95% CI: 1.67-13.29; P = 0.004) for experiencing an SAE. Conclusions: TS of FAV has improved over time, and failure is associated with smaller fetal left heart sizes. SAEs are common and are associated with smaller left hearts and longer procedure times.