Hydrops fetalis in the stillborn: a series from the central region of Thailand

Evaluation of cardiac findings using speckle-tracking echocardiography in fetuses with hemoglobin Bart's disease

OBJECTIVE

Hemoglobin (Hb) Bart's disease is a severe manifestation of alpha-thalassemia, resulting in fetal tissue hypoxia and severe anemia. There is limited research available on assessing speckle-tracking analysis of the fetal heart as a response to fetal anemia caused by Hb Bart's disease. This study aimed to assess the diagnostic performance of fetal cardiac measurements derived from speckle-tracking analysis to identify fetuses with Bart's anemia between 17 and 24 weeks of gestation.

METHODS

This prospective cohort study included 115 women with singleton pregnancies at risk for fetal Hb Bart's disease who underwent either amniocentesis or cordocentesis at Siriraj Hospital, Bangkok, Thailand, in the period between January 2019 and January 2021. Speckle-tracking analysis of the fetal heart was performed in the four-chamber view (4CV), assessing ventricular size and shape, ventricular contractility and left ventricular function, prior to invasive prenatal testing. Logistic regression analysis was used to determine significant cardiac predictors and calculate the probability of a fetus having Hb Bart's anemia.

RESULTS

Among the cohort, 38 (33.0%) fetuses were diagnosed with Hb Bart's disease, and of these, nine (23.7%) cases exhibited fetal hydrops. In comparison to the control group, affected fetuses displayed enlargement of the 4CV, with a globular shape of the right ventricular chamber. Additionally, there were significant reductions in both global and longitudinal left ventricular contractility in non-hydropic affected fetuses compared with the controls. At mid-gestation, no significant differences were observed in transverse contractility or left ventricular function, except for the ejection fraction, between the two groups. Based on logistic regression analysis, combined cardiac measurements derived from speckle-tracking analysis, as a function of head circumference, could differentiate non-hydropic fetuses with Hb Bart's anemia from unaffected fetuses, achieving a sensitivity of 100%, specificity of 98.7% and overall accuracy of 99.1%.

CONCLUSIONS

Speckle-tracking analysis of the fetal heart has the potential to accurately identify early fetal cardiac changes during the second trimester in individuals with Bart's anemia. These findings not only offer a novel predictive marker for Hb Bart's anemia, but also help address the question of the underlying mechanisms of heart failure associated with fetal anemia. © 2024 The Author(s). Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Placenta-Derived Extracellular Vesicles in Pregnancy Complications and Prospects on a Liquid Biopsy for Hemoglobin Bart's Disease

Extracellular vesicles (EVs) are nano-scaled vesicles released from all cell types into extracellular fluids and specifically contain signature molecules of the original cells and tissues, including the placenta. Placenta-derived EVs can be detected in maternal circulation at as early as six weeks of gestation, and their release can be triggered by the oxygen level and glucose concentration. Placental-associated complications such as preeclampsia, fetal growth restriction, and gestational diabetes have alterations in placenta-derived EVs in maternal plasma, and this can be used as a liquid biopsy for the diagnosis, prediction, and monitoring of such pregnancy complications. Alpha-thalassemia major ("homozygous alpha-thalassemia-1") or hemoglobin Bart's disease is the most severe form of thalassemia disease, and this condition is lethal for the fetus. Women with Bart's hydrops fetalis demonstrate signs of placental hypoxia and placentomegaly, thereby placenta-derived EVs provide an opportunity for a non-invasive liquid biopsy of this lethal condition. In this article, we introduced clinical features and current diagnostic markers of Bart's hydrops fetalis, extensively summarize the characteristics and biology of placenta-derived EVs, and discuss the challenges and opportunities of placenta-derived EVs as part of diagnostic tests for placental complications focusing on Bart's hydrop fetalis.

Hydrops fetalis in a cohort of 3,137 stillbirths and second trimester miscarriages

Hydrops fetalis was diagnosed in 277 (9%) of 3,137 fetuses referred to the Wisconsin Stillbirth Service Program (WiSSP) for etiologic evaluation of stillbirth or second trimester miscarriage. Hydrops was clinically recognized at delivery in only about half the cases, while the remainder were diagnosed at autopsy or during evaluation of records, photographs, and radiographs. The peak incidence of hydrops was at 20-28 weeks. Hydropic fetuses were also frequent before 20 weeks but became increasingly rare toward term. The most frequent identifiable underlying cause was chromosomal (29%), followed by other syndromes (14%), and more distantly by cardiac (6%) and other single system disorders. While the overall prevalence of hydrops and chromosomal causes was comparable to other autopsy series, the frequency of nonchromosomal syndromes was higher, reflecting increased attention to syndrome identification. Lethal multiple pterygium syndrome (LMPS) was identified retrospectively in 17 cases, accounting for 6% of all hydrops; 3/17 had a previous affected sib, emphasizing the importance of accurate diagnosis and counseling. Depending on the underlying cause, hydropic fetuses may be either small (if the cause is chromosomal or LMPS) or large (in cases with other syndromes or cardiac causes) for gestational age. The relatively large number in the "idiopathic" group in WiSSP (104/277; 38%) is probably due to variability of autopsies at local hospitals and limited laboratory data. Improved recognition of hydrops and testing directed at diagnosis of specific underlying causes can lead to improved counseling for families.

Pregnancy in Thalassemia

Therapeutic advances, including the availability of oral iron chelators and new non-invasive methods for early detection and treatment of iron overload, have significantly improved the life expectancy and quality of thalassemia patients, with a consequent increase in their reproductive potential and desire to have children. Hundreds of pregnancies have been reported so far, highlighting that women carefully managed in the preconception phase usually carry out a successful gestation and labor, both in case of spontaneous conception and assisted reproductive techniques. A multidisciplinary team including a cardiologist, an endocrinologist, and a gynecologist, under the supervision of an expert in beta-thalassemia, should be involved.

During pregnancy, a close follow-up of maternal disorders and of the baby’s status is recommended. Hemoglobin should be maintained over 10 g/dL to allow normal fetal growth. Chelators are not recommended; nevertheless, it may be reasonable to consider restarting chelation therapy with desferrioxamine towards the end of the second trimester when the potential benefits outweigh the potential fetal risk.

Women with non-transfusion-dependent thalassemia who have never previously been transfused or who have received only minimal transfusion therapy are at risk of severe alloimmune anemia if blood transfusions are required during pregnancy. Since pregnancy increases the risk of thrombosis three-fold to four-fold and thalassemia is also a hypercoagulable state, the recommendation is to keep women who are at higher risk -such as those who are not regularly transfused and those splenectomised- on prophylaxis during pregnancy and the postpartum period.

Risk factors and causes of stillbirths among pregnant women in Pakistan

BACKGROUND

Globally 3 million stillbirths occur per year, and Pakistan is ranked 3rd among the countries having the highest burden. Despite being a major public health problem, efforts to reduce this figure are insufficient.

OBJECTIVE

The aim of the study was to identify and measure the inequalities in stillbirth associated risk factors, causes and fertility risk behaviors.

METHODS

Data were derived from the Pakistan Demographic and Health Surveys (PDHS) 1990-2013. Inequalities on determinants were evaluated using rate differences and rate ratios; time trends computed with annualized reduction rate (ARR).

RESULTS

Overall ARR determined for stillbirth was -12.52 percent per annum. The high ARR were recorded for mothers age <20, urban areas, educated mothers and for highest wealth quintile. The relative inequalities were most pronounced for wealth quintiles, education and age of mothers. Stillbirth causes were unexplained antepartum (33%), unexplained intrapartum (21%), intrapartum asphyxia (21%) and antepartum maternal disorders (19%). The high fertility risk behavior was found in mothers with age >34 and birth order >3.

CONCLUSION

The study concluded that to achieve gain in child survival, there is need to promote antenatal care, birth spacing, and family planning programs in developing countries.

Cardiac Findings in Fetal and Pediatric Autopsies: A 15-Year Retrospective Review

INTRODUCTION

Congenital heart defects (CHDs) carry significant morbidity and mortality in pediatric patients. This study determined the spectrum of CHDs based on fetal and pediatric autopsies.

METHODS

Autopsy reports over a 15-year period were reviewed. Postmortem findings were correlated with echocardiography records.

RESULTS

From 608 autopsies, 119 cases with CHDs were identified (11% of fetal, 53% of neonatal, 18% of infant, and 4.5% of childhood autopsies). Persistent left superior vena cava was the most common individual defect. 41% of cases had extracardiac malformations. 18.5% of cases had chromosomal abnormalities. Prenatal echocardiography was available in 52 cases, showing 85% correlation with autopsy findings. Defects missed by echocardiography were generally of mild severity.

CONCLUSION

Postmortem examination is important to delineate the anatomy of CHDs, and recognize extracardiac malformations for identification of possible genetic syndromes. This information can be used for parental counseling and for assessment of accuracy of pre-mortem imaging studies.

Fetal isovolumetric time intervals as a marker of abnormal cardiac function in fetal anemia from homozygous alpha thalassemia-1 disease

OBJECTIVE

To determine whether fetal isovolumetric time intervals can be an early sonographic marker of fetal anemia in fetuses with homozygous alpha thalassemia-1.

METHODS

Pregnancies at risk for fetal homozygous alpha thalassemia-1 disease at 18-22 weeks were recruited before cordocentesis for hemoglobin typing. Isovolumetric contraction time (ICT) and isovolumetric relaxation time (IRT) intervals were measured by placing pulsed wave Doppler sample volume within the left ventricle to obtain the mitral and aortic waveform. Time intervals were compared between the affected group of homozygous alpha thalassemia-1 fetuses and the unaffected group.

RESULTS

Among 70 fetuses at risk, 28 cases were diagnosed as affected by homozygous alpha thalassemia-1 disease. Mean ICT and ICT + IRT intervals in the affected group were significantly longer than in the unaffected group (47.9 ± 12.5 ms vs 35.0 ± 6.7 ms, p < 0.001; and 96.2 ± 13.6 ms vs 80.9 ± 10.6 ms, p < 0.001. ICT effectively predicted affected fetuses with 71.4% sensitivity and 78.6% specificity using a cutoff value ≥40 ms.

CONCLUSIONS

Isovolumetric contraction time was significantly prolonged in fetal anemia from homozygous alpha thalassemia-1 during the early stage of hydropic changes. Because of its simple measurement and high efficacy, ICT can be a useful marker for prenatal screening of abnormal cardiac function in fetal anemia. © 2017 John Wiley & Sons, Ltd.

Pulmonary Neuroendocrine Cell Hyperplasia in Hemoglobin Bart-induced Hydrops Fetalis: A model for Chronic Intrauterine Hypoxia

The pulmonary neuroendocrine system includes pulmonary neuroendocrine cells (PNECs) and neuroepithelial bodies (NEBs) that are distributed throughout respiratory epithelium and regulate lung growth and maturation antenatally. Abnormalities in this system have been linked to many hypoxia-associated pediatric pulmonary disorders. Hemoglobin (Hb) Bart disease is a severe form of α-thalassemia resulting in marked intrauterine hypoxia with hydrops fetalis (HF) and usually death in utero. Affected fetuses can serve as a naturally occurring human model for the effects of intrauterine hypoxia, and we postulated that these effects should include changes in the pulmonary neuroendocrine system. Bombesin immunostaining was used to assess PNECs and NEBs in stillborn fetuses with Hb Bart HF ( n = 16) and with HF from other causes ( n = 14) in comparison to non-HF controls. Hb Bart HF showed a significant increase in the proportion of PNECs in respiratory epithelium ( P = .002), mean number of NEB nuclei ( P = .03), and mean size of NEBs ( P = .002), compared to normal non-HF controls. Significant differences were not observed between HF due to other causes and non-HF controls with normal lungs. Non-HF controls with pulmonary hypoplasia showed significant increases in PNECs compared to HF cases not due to Hb Bart HF, implying HF alone does not cause such increases. In contrast, no significant differences were noted between non-HF controls with pulmonary hypoplasia and Hb Bart cases. Hb Bart HF may provide a useful model for studying the pulmonary neuroendocrine system under chronic intrauterine hypoxia.

Causes of and factors associated with stillbirth in low- and middle-income countries: a systematic literature review

BACKGROUND

Annually, 2.6 million stillbirths occur worldwide, 98% in developing countries. It is crucial that we understand causes and contributing factors.

METHODS

We conducted a systematic review of studies reporting factors associated with and cause(s) of stillbirth in low- and middle-income countries (2000-13). Narrative synthesis to compare similarities and differences between studies with similar outcome categories.

MAIN RESULTS

A total of 142 studies with 2.1% from low-income settings were investigated; most report on stillbirths occurring at health facility level. Definition of stillbirth varied; 10.6% of studies (mainly upper middle-income countries) used a cut-off point of ≥22 weeks of gestation and 32.4% (mainly lower income countries) used ≥28 weeks of gestation. Factors reported to be associated with stillbirth include poverty and lack of education, maternal age (>35 or <20 years), parity (1, ≥5), lack of antenatal care, prematurity, low birthweight, and previous stillbirth. The most frequently reported cause of stillbirth was maternal factors (8-50%) including syphilis, positive HIV status with low CD4 count, malaria and diabetes. Congenital anomalies are reported to account for 2.1-33.3% of stillbirths, placental causes (7.4-42%), asphyxia and birth trauma (3.1-25%), umbilical problems (2.9-33.3%), and amniotic and uterine factors (6.5-10.7%). Seven different classification systems were identified but applied in only 22% of studies that could have used a classification system. A high percentage of stillbirths remain 'unclassified' (3.8-57.4%).

CONCLUSION

To build capacity for perinatal death audit, clear guidelines and a suitable classification system to assign cause of death must be developed. Existing classification systems may need to be adapted. Better data and more data are urgently needed.

Second trimester maternal serum alpha-fetoprotein (MSAFP) as predictor of fetal hemoglobin Bart's disease

OBJECTIVE

The objective of this study is to evaluate the efficacy of maternal serum alpha-fetoprotein (MSAFP) levels in predicting hemoglobin (Hb) Bart's fetus.

MATERIALS AND METHODS

A total of 199 pregnancies at risk of fetal Hb Bart's disease at 18 to 22 weeks were enrolled. Before performing cordocentesis for the Hb typing analysis, the MSAFP levels were analyzed, and sonographic markers (middle cerebral artery peak systolic velocity, cardiothoracic ratio and placental thickness) were measured. The detection rates of MSAFP and the sonographic markers in predicting fetuses affected by Hb Bart's disease were evaluated.

RESULTS

The MSAFP levels were significantly higher in pregnant women carrying affected fetuses (47 cases) than in those with unaffected fetuses (2.09 MoM vs 1.18 MoM, P < 0.001). MSAFP as a single marker effectively predicted fetal Hb Bart's disease (area under curve receiver operating characteristic 0.832, 95% CI 0.752-0.911), with 87.2% sensitivity and 74.5% specificity using a cutoff value greater than 1.50 MoM. A combination of MSAFP with sonographic markers gave detection rates in the range of 91.5% to 100%.

CONCLUSION

Second trimester MSAFP levels are significantly higher in pregnancies with Hb Bart's fetus. MSAFP as a single marker is relatively effective in Hb Bart's prenatal screening. A high detection rate is achieved when MSAFP is used in combination with sonographic markers.

Histologic changes in the adrenal gland reflect fetal distress in hydrops fetalis

The distribution of lipid in the fetal adrenal cortex is reported to correlate with the duration of hypoxia and degree of fetal stress. The original studies were based on Oil Red O staining, requiring frozen tissue that is often not available. To investigate the reliability of these observations, the distribution of lipid in the fetal adrenal cortex was studied in hydrops fetalis (HF) of different etiologies, using immunostaining for adipophilin on formalin-fixed material. Twenty cases of HF due to hemoglobin (Hb) Bart were compared to 34 cases of HF due to other causes. In the fetal zone, lipid distribution was more diffuse in Hb Bart HF compared to other causes of HF, including those due to anemia, supporting the concept that increased lipid in the fetal zone is associated with severity of hypoxia. A more diffuse distribution of lipid correlated with adrenal cytomegaly (P < 0.01) and extramedullary hematopoiesis (P < 0.01) but not Hb level (P  =  0.68) nor compact cell change (P  =  0.7) or cystic degeneration (P  =  0.07) in the definitive zone. A greater degree of cystic degeneration correlated with lower gestational age, rather than the specific etiology of HF. Thus, cystic degeneration is more a reflection of the onset of fetal stress than severity. The combined histologic changes in the fetal and definitive zones of the adrenal gland provide complementary information about fetal status in HF. Immnunostaining for adipophilin circumvents the need for frozen tissue for assessing lipid content by Oil Red O staining, facilitating studies based on archival material.

Comparison of cardiac troponin T and N-terminal pro-B-type natriuretic peptide between fetuses with hemoglobin Bart's disease and nonanemic fetuses

OBJECTIVE

The objective of this study was to compare the levels of fetal serum cardiac troponin T (cTnT), representing cardiac injury, and N-terminal pro-B-type natriuretic peptide (nt-proBNP), representing cardiac volume overload, between fetuses affected and not affected by hemoglobin (Hb) Bart's disease, as well as between anemic and nonanemic fetuses.

METHODS

One hundred fourteen pregnancies at risk for fetal Hb Bart's disease scheduled for cordocentesis at 18 to 22 weeks were recruited into the study. Fetal blood was collected to test for cTnT, nt-proBNP and Hb levels as well as Hb typing.

RESULTS

Serum nt-proBNP was significantly higher in Hb Bart's fetuses (24 cases) than in unaffected fetuses (63 cases), whereas cTnT was significantly lower in the affected group than in the unaffected group. The serum nt-proBNP levels significantly increased with the degree of fetal anemia; cTnT levels decreased in fetuses with high degree of anemia.

CONCLUSIONS

At mid-pregnancy, nt-proBNP was significantly higher in fetuses with Hb Bart's disease than in nonanemic fetuses; cTnT was significantly lower in anemic than in normal fetuses. This study suggests that cardiomegaly from fetal anemia in early gestation is not associated with fetal cardiac injury or myocardial dysfunction but presents as cardiac volume overload from a compensatory process to maintain adequate tissue oxygenation.

Loss of β2-spectrin prevents cardiomyocyte differentiation and heart development

AIMS

β2-Spectrin is an actin-binding protein that plays an important role in membrane integrity and the transforming growth factor (TGF)-β signalling pathway as an adaptor for Smads. Loss of β2-spectrin in mice (Spnb2(-/-)) results in embryonic lethality with gastrointestinal, liver, neural, and heart abnormalities that are similar to those in Smad2(+/-)Smad3(+/-) mice. However, to date, the role of β2-spectrin in embryogenesis, particularly in heart development, has been poorly delineated. Here, we demonstrated that β2-spectrin is required for the survival and differentiation of cardiomyocytes, and its loss resulted in defects in heart development with failure of ventricular wall thickening.

METHODS AND RESULTS

Disruption of β2-spectrin in primary muscle cells not only inhibited TGF-β/Smad signalling, but also reduced the expression of the cardiomyocyte differentiation markers Nkx2.5, dystrophin, and α-smooth muscle actin (α-SMA). Furthermore, cytoskeletal networks of dystrophin, F-actin, and α-SMA in cardiomyocytes were disorganized upon loss of β2-spectrin. In addition, deletion of β2-spectrin in mice (Spnb2(tm1a/tm1a)) prevented proper development of the heart in association with disintegration of dystrophin structure and markedly reduced survival.

CONCLUSION

These data suggest that β2-spectrin deficiency leads to inactivation of TGF-β/Smad signalling and contributes to dysregulation of the cell cycle, proliferation, differentiation, and the cytoskeletal network, and it leads to defective heart development. Our data demonstrate that β2-spectrin is required for proper development of the heart and that disruption of β2-spectrin is a potential underlying cause of congenital heart defects.

Comparison of maternal serum PlGF and sFlt-1 between pregnancies with and without fetal hemoglobin Bart's disease

OBJECTIVE

The aim of this study was to compare the levels of maternal serum placental growth factor (PlGF) and soluble fms-like tyrosine kinase-1 (sFlt-1) between pregnancies with fetal hemoglobin (Hb) Bart's disease and unaffected pregnancies.

METHODS

Ninety-one pregnancies at risk for fetal Hb Bart's disease scheduled for cordocentesis at 18-22 weeks were recruited into the study. Maternal serum PlGF and sFlt-1 concentrations were measured before cordocentesis. Fetal blood samples were collected for thalassemia diagnosis based on fetal Hb typing using high-performance liquid chromatography. PlGF, sFlt-1, and sFlt-1/PlGF ratio were compared between the fetal Hb Bart's group and the non-Hb Bart's group (normal Hb typing or α-thalassemia-1 carrier).

RESULTS

Maternal serum concentration of PlGF was significantly higher in women with fetal Hb Bart's disease (18 cases) than those with unaffected fetuses (71 cases) (P = 0.008), whereas the concentration of sFlt-1 was not significantly different (P = 0.139). However, the sFlt-1/PlGF ratio was significantly lower in women with fetal Hb Bart's disease than those with unaffected fetuses (P = 0.001).

CONCLUSION

Placental growth factor may help differentiate affected from unaffected fetuses among pregnancies at risk, though further studies are needed to confirm its usefulness. In addition, preeclampsia prediction using these markers may be unreliable in pregnancies with placental dysfunction secondary to severe fetal anemia.

Peripheral villous stromal hyperplasia: a distinctive placental lesion in hemoglobin bart hydrops fetalis

In hydrops fetalis (HF) the placenta can be markedly enlarged and the villi show stromal edema, increased Hofbauer cells, and reduced numbers of capillaries. Hemoglobin (Hb) Bart is the most severe form of thalassemia, causing HF due to profound anemia. We report a previously undescribed histologic finding based on a review of Hb Bart HF cases, termed "peripheral villous stromal hypercellularity." This change was noted in 15 of 18 (83%) placentas with Hb Bart HF but not in placentas of 21 cases of HF due to other causes, including 11 cases involving anemia. The hyperplastic stromal cells were determined to be myofibroblastic by immunohistochemistry and electron microscopy, associated with a more complex capillary network in villi than is seen with other causes of HF. The authors hypothesize that this angiogenesis in villi is a response to fetal anemia from Hb Bart. In turn, there is increased villous blood flow, resulting in edematous villous stroma, leading to narrowing of the intervillous space in the placenta. Hyperplasia of myofibroblasts might then be a compensatory change, in that contraction by these cells would reduce the vascular lumina and the size of placental villi, thereby widening the intervillous space to improve capacity for maternal blood circulation. Curiously, this histologic change was restricted to cases of HF caused by Hb Bart. We speculate that in Hb Bart disease, the hypoxia and hydrops develop earlier in gestation, compared to other causes of HF, allowing the time for these adaptive changes to occur in the placenta.

The contribution of extramedullary hematopoiesis to hepatomegaly in anemic hydrops fetalis: a study in alpha-thalassemia hydrops fetalis

Massive hepatomegaly is a common finding in hydrops fetalis (HF) arising from hemoglobinopathies. It has been suggested that extramedullary hematopoiesis, which is markedly increased in response to anemia, plays a principal role in hepatomegaly via sinusoidal obstruction and distortion of the intrahepatic architecture. To test this concept, the authors compared 20 cases of α-thalassemia (hemoglobin Bart, 15 cases; hemoglobin H, 5 cases) with 19 cases of HF arising from other causes and 39 control nonhydrops cases. The mean liver weight in α-thalassemia cases was significantly heavier than in control cases and in hydrops fetalis cases due to other causes (P < 0.01). This was not explainable on the basis of extramedullary hematopoiesis (erythropoiesis or myelopoiesis) or hemosiderin deposition, since cases of HF from other causes, especially related to anemia, showed similar findings to α-thalassemia cases. While these processes no doubt contribute to hepatic weight, the major factor would still be high-output cardiac failure causing hepatic congestion.

Adrenal cytomegaly is a frequent pathologic finding in hemoglobin bart hydrops fetalis

Adrenocortical cytomegaly (AC) is a relatively uncommon phenomenon but tends to occur in certain situations, including specific congenital anomalies and hydrops due to maternal-fetal Rhesus incompatibility. Because the pathology in the latter condition does not differ greatly from hemoglobin (Hb) Bart hydrops fetalis, we performed a retrospective review of fetal and perinatal autopsy cases with Hb Bart to determine the prevalence of AC in that condition. Over a 10-year period (2001-2010) at King Chulalongkorn Memorial Hospital, there were 16 hydropic cases confirmed to have Hb Bart. Adrenocortical cytomegaly was found in 13 cases (81%). For comparison, we determined the occurrence of AC in cases of hydrops fetalis not due to Hb Bart (n  =  33) and a heterogeneous group of congenital anomalies (n  =  34). Adrenocortical cytomegaly was identified in only 1 case of Beckwith-Wiedemann syndrome and 2 cases of anencephaly. Thus, AC is a common finding in cases of Hb Bart, a finding not previously documented. Moreover, our study suggests that Hb Bart is one of the conditions most commonly associated with AC. The reasons for this are not known. The mean Hb levels for the hydrops cases with Hb Bart and those with other forms of anemia showed no significant difference (P  =  0.63), nor was there any significant difference in Hb levels between cases of Hb Bart with and without AC. Nonetheless, the consistency of AC in cases of Hb Bart suggests that further study of this particular group of patients might shed light on the pathogenesis of this poorly understood pathologic finding.