A new strategy for prenatal diagnosis of homozygous alpha(0)-thalassemia

MRI Reference Ranges for Fetal Cardiothoracic Ratio of Diameter, Area, and Circumference from 21 to 38 Weeks Gestational Age

BACKGROUND

Whether fetal cardiothoracic ratio (CTR) is constant or increasing with gestational age (GA) is controversial. The majority of the fetal CTR data has been obtained through ultrasound.

PURPOSE

To retrospectively analyze CTR of diameter, area, and circumference on prenatal MR images in a low-risk population of singleton pregnancies, and to clarify its diagnostic value.

STUDY TYPE

Retrospective.

SUBJECTS

1024 low-risk singleton pregnancies undergoing MRI.

FIELD STRENGTH

Balanced steady state free precession sequence and single shot-fast spin echo sequence at 1.5 Tesla.

ASSESSMENT

Pregnancy clinical data were recorded and diameter, area, and circumference of the fetal heart and thorax were measured by two researchers with 6 and 7 years of radiology experience, respectively, and their variation with GA was investigated. The relationship between CTRs with GA was also investigated. Finally, the value of CTR in the diagnosis of fetuses with abnormal development was explored by using receiver operating characteristic (ROC) curves.

STATISTICAL TESTS

Linear regression and ROC curves. A P value <0.05 was considered significant.

RESULTS

There were significant positive linear correlations (R2 > 0.7, P < 0.0001) between the diameter, area, and circumference of the heart and thorax with GA. The CTRs remain constant values and do not change with GA. The 5th, 50th, and 95th percentiles of the CTR in 21-38 weeks GA were 0.32, 0.39, and 0.48 respectively. The corresponding percentiles for the area ratio were 0.15, 0.21 and 0.27, respectively, and for the circumference ratio were 0.40, 0.46, and 0.52, respectively. Based on ROC curves of CTR with three methods, the area under curves (AUCs) were up to 0.95, the sensitivity and the specificity were more than 88%.

DATA CONCLUSION

Reference ranges of fetal CTR were established using MRI, which remain constant. These may be helpful in making a definitive diagnosis in fetuses with abnormal development.

LEVEL OF EVIDENCE: 4

TECHNICAL EFFICACY

Stage 2.

Comparing three cardiothoracic ratio measurement techniques and creating multivariable scoring system to predict Bart's hydrops fetalis at 17-22 weeks' gestation

To assess the diagnostic performance of three cardiothoracic (CT) ratio techniques, including diameter, circumference, and area, for predicting hemoglobin (Hb) Bart's disease between 17 and 22 weeks' gestation, and to create a multivariable scoring system using multiple ultrasound markers. Before invasive testing, three CT ratio techniques and other ultrasound markers were obtained in 151 singleton pregnancies at risk of Hb Bart's disease. CT diameter ratio demonstrated the highest sensitivity among the other techniques. Significant predictors included CT diameter ratio > 0.5, middle cerebral artery-peak systolic velocity (MCA-PSV) > 1.5 multiples of the median, and placental thickness > 3 cm. MCA-PSV exhibited the highest sensitivity (97.8%) in predicting affected fetuses. A multivariable scoring achieved excellent sensitivity (100%) and specificity (84.9%) for disease prediction. CT diameter ratio exhibited slightly outperforming the other techniques. Increased MCA-PSV was the most valuable ultrasound marker. Multivariable scoring surpassed single-parameter analysis in predictive capabilities.

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.

Thick Placenta in Pregnancy: A Review

Importance

A thickened placenta is easily identified on ultrasound and provides insight into maternal and fetal wellbeing as well as underlying structural and physiologic anomalies.

Objectives

The aim of this study was to review the literature to clarify what classifies a placenta as "thickened" and to review the associated incidence, maternal and fetal comorbidities, and management during pregnancy.

Evidence Acquisition

Electronic databases (PubMed and Web of Science) were searched from 2000 to 2020 in the English language. Studies were selected that examined associations between placental thickness, potential etiologies, and obstetric outcomes.

Results

There were 140 abstracts identified. After reviewing the articles, 60 were used in this review. Routine assessment of the placenta in the prenatal period is an easy and inexpensive way to assess the maternal and fetal patients. The criteria for a "thickened placenta" vary between studies based on gestational age, placental location, measurement technique, and maternal or fetal factors. Whereas most suggest thickness exceeding 4 cm is pathologic, a review had a threshold of 6 cm in the third trimester to classify placentomegaly. Several maternal and fetal conditions have been associated with a thickened placenta, such as obesity, parity, anemia, diabetes, preeclampsia, cardiac dysfunction, infection, assisted reproductive technology, multiple pregnancy, sacrococcygeal teratomas, and Beckwith-Wiedemann syndrome. A thickened placenta in pregnancy is associated with a higher incidence of adverse pregnancy outcomes and neonatal morbidity and mortality.

Conclusions

The literature is clear that early evaluation of the placenta using ultrasound should be a standard practice. A thickened placenta found on routine imaging should prompt a more thorough investigation to determine the etiology of the placentomegaly. At the time of this literature review, there are no recommendations regarding modality or frequency of antenatal surveillance in pregnancies complicated by a thickened placenta. However, serial ultrasounds and weekly antenatal testing in the third trimester should be considered.

Relevance

A thickened placenta has been associated with a variety of maternal and fetal conditions and increases the risk of adverse pregnancy outcomes and neonatal morbidity and mortality.

Nomograms of fetal cardiothoracic ratio from 17 to 37 weeks' gestation as assessed by three different measurement techniques and their correlation with gestational age

OBJECTIVE

To create nomograms for fetal cardiothoracic (CT) ratio as assessed by three different 2-dimensional sonographic measurements, including CT diameter, circumference, and area ratios, in Thai fetuses with a gestational age (GA) of 17-37 weeks, and to evaluate both their correlation with GA or biparietal diameter (BPD) and variability among the three measurement methods.

METHODS

Two-dimensional sonographic measurements of fetal CT ratio in 4-chamber view were assessed by three different measurement techniques. The 95% reference intervals and Z-scores of all measurement methods based on GA or BPD were constructed. Intraclass correlation coefficients (ICC) for the reproducibility of each technique were compared.

RESULTS

A total of 511 uncomplicated singleton pregnancies were included. The fetal CT ratio values by all measurement techniques gradually and smoothly increased with increasing GA and BPD. The fetal CT circumference ratio showed the least correlation with both GA and BPD. The intraobserver and interobserver reliability coefficients of all techniques demonstrated almost excellent agreement (all ICCs at least 0.87).

CONCLUSION

Reference intervals and Z-score reference ranges were developed using three different techniques for fetal CT ratio with a GA of 17-37 weeks. These nomograms are a simple and reliable screening tool for identifying abnormal fetal heart size.

Ultrasound Features of Fetal Anemia Lessons From Hemoglobin Bart Disease

Insights gained from this review are as follows: (1) Ultrasound is highly effective in early detection of fetal hemoglobin (Hb) Bart disease. (2) The most sensitive parameters in predicting Hb Bart anemia appear to be the cardiac diameter-to-thoracic diameter ratio, middle cerebral artery peak systolic velocity, and placental thickness. (3) Several other ultrasound markers are helpful in increasing specificity, such as hepatosplenomegaly. (4) Hydrops fetalis is not a consequence of heart failure but rather of hypervolemia and high vascular permeability of fetuses, whereas heart failure is a very late consequence of a long-standing overworked heart. (5) Management guidelines for fetuses at risk of Hb Bart disease are proposed.

Characterisation of two unusual cases of haemoglobin Bart's hydrops foetalis caused by -SEA and large novel α-globin gene cluster deletions

BACKGROUND

We describe 2 unusual haemoglobin (Hb) Bart's hydrops cases that could not be explained by traditional factors.Case presentation: Two families with a diagnosis or history of foetal hydrops were enrolled. A suspension-array system was used to detect the 23 most frequent mutations in southern China. Multiplex ligation-dependent probe amplification (MLPA) was used to screen for possible deletions. Precise characterisation of the breakpoints of the novel variants and uniparental disomy analysis were performed using a single nucleotide polymorphism (SNP) array. Quantitative fluorescence PCR was used to eliminate maternal cell contamination and nonpaternity. In case 1, the suspension-array system indicated a maternal heterozygous (-SEA/) deletion, and the paternal sample was negative. The foetal hydrops was caused by the maternal (-SEA/) deletion and a de novo α-globin gene deletion (-193). In case 2, the paternal sample had a heterozygous (-SEA/) deletion, and MLPA and SNP array analysis revealed a large maternal deletion (-227) that encompassed the α-globin gene, which explained the history of Hb Bart's foetal hydrops.

CONCLUSIONS

Our cases describe 2 new α0-thalassaemia deletions and illustrate the importance of using a combination of methods to detect rare types of α-thalassaemia.

Foetal haemodynamic response to anaemia

This study aims to update new knowledge regarding foetal cardiovascular response to anaemia, using foetal haemoglobin Bart's disease as a study model. Original research articles, review articles, and guidelines were narratively reviewed and comprehensively validated. The main foetal cardiovascular changes in response to anaemia are consequences of hypervolaemia and increased cardiac output to meet tissue oxygen requirement. New challenging insights are as follows: (i) the earliest morphological change is an increase in cardiac size and remodelling of the sphericity (an increase in diameter more pronounced than that in long axis) followed by several markers, such as placentomegaly and hepatosplenomegaly. (ii) The earliest functional change is increased peak systolic velocity of the red blood cells because of low viscosity, especially in the middle cerebral artery. (iii) The foetal heart has very high reserve potentials to cope with anaemia: increasing workload without increased central venous pressure and increased myocardial performance without compromising shortening fraction. This hard‐working period with good performance lasts long, including most part of the second and third trimester. (iv) At the time cardiomegaly myocardial cellular damage has already occurred, in spite of good cardiac function. (v) Anaemic hydrops foetalis is mainly due to hypervolaemia, hypoalbuminaemia, and high vascular permeability, not heart failure. (vi) Foetal heart failure occurs only when the adaptive mechanism becomes exhausted or long after the development of anaemic hydrops foetalis. Heart failure is a very late result of a longstanding overworked heart. (vii) Ultrasound is highly effective in the detection of foetal response to anaemia. An increase in cardiac size and middle cerebral artery is very helpful in predicting the affected foetuses in pre‐hydropic phase. (viii) Theoretically, intrauterine treatment of anaemic hydrops results in satisfactory outcomes as long as cardiac function is normal, but intrauterine intervention should be strongly considered in pre‐hydropic phase because myocardial cell damage could have already occurred in this phase or early hydropic phase. Anaemic hydrops foetalis is not primarily caused by heart failure as commonly advocated, but it is rather a consequence of hypervolaemia, hypoalbuminaemia, and high vascular permeability while heart failure is a very late consequence of a longstanding overworked heart. New insights gained from this review may be useful to base clinical practice on which sonographic markers imply significant pathological changes, how ultrasound can be helpful in early detection of anaemic response, when intrauterine transfusion for anaemia due to non‐lethal causes should be administered, etc.

Reproductive health issues in female patients with beta-thalassaemia major: a narrative literature review

β-thalassaemia major (BTM) has a high prevalence worldwide and is associated with considerable morbidity and mortality. The aim of this review is to provide an illustrative overview of the reproductive health and pregnancy related issues in females with β-thalassaemia. A literature search was performed in four international databases (1980-2018) to identify the potentially relevant articles. Common reproductive health disorders are hypo-gonadotrophic hypogonadism, infertility, delayed or absent sexual development, diabetes, hypothyroidism, hypoparathyroidism, osteopenia, preeclampsia, gestational hypertension, polyhydramnios, oligohydramnios, thrombosis, renal failure, peripheral vascular resistance, placenta previa, pleural effusion and pulmonary hypertension. Many of those aspects are related to iron overload and to ineffective erythropoiesis. Foetal complications include neural tube defects, abnormalities in different organs, spontaneous abortion, foetal loss, preterm birth, foetal growth restriction and low birth weight. Antenatal screening and accurate genetic prenatal examinations are effective measures to early diagnosis of thalassaemia and a detailed plan for management of pregnancies in BTM is important for favourable maternal and foetal outcome.

Z Score Reference Ranges of Fetal Cardiothoracic Diameter Ratio

OBJECTIVE

This study aims to establish the z score reference ranges of cardiothoracic diameter ratio (CTR) of normal fetuses from 14 to 40 weeks' gestation.

METHOD

A cross-sectional study was conducted on low-risk singleton pregnancies with healthy fetuses. The CTR was performed using simple 2-dimensional sonography on the typical fetal 4-chamber view. The reference ranges were constructed according to gestational age (GA), biparietal diameter (BPD), and head circumference (HC) as independent variables based on the best-fit models, both mean and standard deviation (SD).

RESULTS

A total of 683 fetuses were measured for CTR. The best-fit equations for the mean and SD as a function of GA, BPD, and HC are as follows: (1) CTR = 0.365 + 0.004 × GA in weeks (SD = 0.031 + 0.001 × GA); (2) CTR = 0.373 + 0.014 × BPD in cm (SD = 0.034 + 0.004 × BPD); and (3) CTR = 0.373 + 0.004 × HC in cm (SD = 0.032 + 0.001 × HC). The CTR was slightly increased with advanced GA, BPD, and HC.

CONCLUSION

Complete nomograms with z score reference ranges of CTR were established throughout pregnancy. These nomograms may be useful to detect cardiac abnormalities.

The best cutoff value of middle cerebral artery peak systolic velocity for the diagnosis of fetal homozygous alpha thalassemia-1 disease

OBJECTIVE

To determine the best cutoff value of middle cerebral artery peak systolic velocity (MCA-PSV) for the diagnosis of fetuses with homozygous alpha thalassemia-1 disease.

METHODS

Pregnancies at risk for fetal homozygous alpha thalassemia-1 disease at 18 to 22 weeks were recruited. MCA-PSV was measured before cordocentesis for hemoglobin typing and complete blood count. The performance of the MCA-PSV for identifying affected fetuses was evaluated using a best cutoff value derived from the receiver operating characteristic (ROC) curve.

RESULTS

Among 142 fetuses at risk, 46 (32.4%) fetuses were diagnosed as affected by homozygous alpha thalassemia-1 disease and were categorized as mild anemia (16.3%), moderate anemia (58.1%), and severe anemia (25.6%). With the best cutoff point of MCA-PSV > 1.30 multiples of the median (MoM) or >30.0 cm/s, the sensitivity for predicting fetal homozygous alpha thalassemia-1 was 100%.

CONCLUSIONS

MCA-PSV > 1.30 MoM is the best cutoff value for the diagnosis of all degrees of fetal anemia from homozygous alpha thalassemia-1 fetuses. Because of its simplicity for interpretation and high efficacy, a cutoff value of MCA-PSV > 30 cm/s can also be used as an alternative marker for fetal anemia screening during 18 to 22 weeks of gestation.

Invasive prenatal diagnosis of α-thalassemia to control Hb Bart's hydrops fetalis syndrome: 15 years of experience

PURPOSE

The aim of the present study was to report experiences with invasive prenatal diagnosis of α-thalassemia for the prevention of Hb Bart's hydrops fetalis syndrome in the Guangxi Zhuang Autonomous Region, China.

METHODS

Pregnant women and their partners who tested positive for α⁰-thalassemia or were diagnosed with HbH diseases were counseled and suggested to undergo a prenatal diagnostic procedure for α-thalassemia. Fetal material was obtained by chorionic villus sampling (CVS) between 9 and 13 weeks of gestation, by amniocentesis between 16 and 24 weeks of gestation and by cordocentesis after 24 weeks of gestation. The α⁰-thalassemia gene types were detected by gap polymerase chain reaction (Gap-PCR). All results were finally confirmed by DNA analysis after delivery or termination of pregnancy.

RESULTS

An invasive prenatal α-thalassemia diagnosis was performed in 3155 cases at risk for Hb Bart's hydrops fetalis syndrome at our hospital from 2002 to 2016. CVS was performed in 1559 cases (49.4%), amniocentesis in 1240 cases (39.3%) and cordocentesis in 356 cases (11.3%). In total, 786 fetuses were diagnosed as Hb Bart's hydrops fetalis syndrome. Among these cases, the α-thalassemia genotype was --^SEA/--^SEA in 784 cases and --^SEA/--^THAI in 2 cases. All affected pregnancies were terminated in time.

CONCLUSIONS

This extensive experience suggests that carrier screening, molecular diagnostics, genetic counselling, and prenatal diagnosis are effective measures to prevent Hb Bart's hydrops fetalis syndrome.

Invasive prenatal diagnosis of fetal thalassemia

Thalassemia is the most common monogenic inherited disease worldwide, affecting individuals originating from many countries to various extents. As the disease requires long-term care, prevention of the homozygous state presents a substantial global disease burden. The comprehensively preventive programs involve carrier detections, molecular diagnostics, genetic counseling, and prenatal diagnosis. Invasive prenatal diagnosis refers to obtaining fetal material by chorionic villus sampling (CVS) at the first trimester, and by amniocentesis or cordocentesis at the second trimester. Molecular diagnosis, which includes multiple techniques that are aimed at the detection of mutations in the α- or β-globin genes, facilitates prenatal diagnosis and definitive diagnosis of the fetus. These are valuable procedures for couples at risk, so that they can be offered options to have healthy offspring. According to local practices and legislation, genetic counseling should accompany the invasive diagnostic procedures, DNA testing, and disclosure of the results. The most critical issue in any type of prenatal molecular testing is maternal cell contamination (MCC), especially when a fetus is found to inherit a particular mutation from the mother. The best practice is to perform MCC studies on all prenatal samples. The recent successful studies of fetal DNA in maternal plasma may allow future prenatal testing that is non-invasive for the fetus and result in significant reduction of invasive diagnostic procedures.

A Program on Noninvasive Prenatal Diagnosis of α-Thalassemia in Mainland China: A Cost-Benefit Analysis

The aim of the present study was to determine the cost effectiveness of a noninvasive prenatal diagnosis (PND) program for α-thalassemia (α-thal) using ultrasound scan. During a 5-year period, 1923 pregnancies at-risk for homozygous α(0)-thal were recruited into the noninvasive PND program. There were 1452 women who avoided invasive testing because of a normal ultrasound scan. The remaining 471 showed abnormal fetal ultrasonographic findings, and invasive testing was recommended. The overall cost of running the noninvasive PND program was US$213,383, while the cost of running the invasive program would have been US$554,810. The total savings were estimated at US$356,499 for women with an unaffected pregnancy with a net saving of US$246 per capita. This study demonstrated that it is cost effective to run a noninvasive PND program for α-thal in an area where the disease is prevalent, and therefore effectively avoiding an invasive test in unaffected pregnancies.

Prenatal diagnosis of thalassemia in twin pregnancies in mainland China

The aim of this study was to describe our experience with prenatal diagnosis of thalassemia in twin pregnancies at a tertiary referral centre in mainland China. All cases of twin pregnancies at risk of α- or β-thalassemias were followed over an eight-year period. There were 32 twin pregnancies at a mean gestation of 14 weeks (range, 11-21 weeks) at risk of thalassemias, including 19 at risk of α-thalassemia and 13 at risk of β-thalassemia. Chorionicity was determined by ultrasound before prenatal diagnosis. In 19 twin pregnancies at risk of α-thalassemia, there were four where both foetuses were affected, 13 where both foetuses were not affected, and two where one foetus was affected and the other one was not affected. In 13 twin pregnancies at risk of β-thalassemia, there were five where both foetuses were affected, six where both foetuses were not affected, and two where one foetus was affected and the other one was not affected. The pregnancies with two affected foetuses were aborted (including four affected by α-thalassemia and five affected by β-thalassemia), and in pregnancies with one normal twin and one affected twin, the affected foetuses were selectively aborted (including two twins affected by α-thalassemia, and two twins affected by β-thalassemia). Efforts should be taken to reduce the risks of the mother and foetuses in prenatal diagnosis without compromising the precise diagnosis.

Fetal Anemia and Hydrops Fetalis Associated with Homozygous Hb Constant Spring (HBA2: c.427T > C)

Hb Constant Spring (Hb CS, HBA2: c.427T > C) is a common nondeletional α-thalassemia (α-thal) that results from a nucleotide substitution at the termination codon of the α2-globin gene. Homozygosity for Hb CS (α(CS)α/α(CS)α) is relatively rare, and generally characterized with mild hemolytic anemia, jaundice, and splenomegaly. In this report we present a fetus with cardiomegaly, pericardial effusion, enlarged placenta and increased middle cerebral artery-peak systolic velocity (MCA-PSV) at 24 weeks' gestation. Fetal blood sampling revealed the severe anemia [hemoglobin (Hb) level being 4.8 g/dL] and Hb H (β4) disease-like hematological findings with Hb Bart's (γ4) level of 17.9%. DNA sequencing of the α-globin genes found that both partners were Hb CS carriers and the fetus was an Hb CS homozygote. Therefore, this was a rare case of homozygous Hb CS which demonstrated an unusual and serious anemia and hydrops fetalis in utero.

Prevention of Hb Bart's (γ4) Disease Associated with the - -(THAI) α(0)-Thalassemia Deletion in Mainland China

α-Thalassemia (α-thal) is a common inherited disease in southern China. The severest form is Hb Bart's (γ4) disease, in which the affected fetuses almost always die in utero or shortly after birth, and the mothers are at high risk for severe morbidity. The most common type of α(0)-thalassemia (α(0)-thal) in southern China is Southeast Asian (- -(SEA)) deletion. Occasionally, Hb Bart's disease, caused by a compound heterozygosity for the - -(SEA) and - -(THAI) α(0)-thal deletions, can also be encountered. In this study, we report our experience with the prevention of Hb Bart's disease associated with the - -(THAI) α(0)-thal deletion. A total of 385 couples at risk for Hb Bart's disease, including seven who tested positive for the - -(SEA) deletion in one partner and the - -(THAI) deletion in the other, were found. Different prenatal procedures were offered, depending on the gestational age at presentation. Sixty-six affected fetuses were diagnosed prenatally; among these, two cases of Hb Bart's disease were compound heterozygotes for the - -(SEA) and - -(THAI) deletions. All affected pregnancies were terminated in time. We also presented a diagnostic protocol for identification of α(0)-thal trait that can reduce the number of samples for detection of the - -(THAI) deletion.

Sonographic markers of fetal α-thalassemia major

α-Thalassemia prevails in Southeast Asia, where α-thalassemia major is a lethal type. Sonography is a helpful and cost-effective screening tool for detecting α-thalassemia major fetuses. The cardiothoracic ratio, placental thickness, and middle cerebral artery peak systolic velocity are most used in clinical practice. These sensitive markers are helpful for evaluation of the hemodynamic status and cardiovascular function of the affected fetuses. They can predict fetal α-thalassemia major and assess the efficacy of treatment noninvasively; therefore, the medical costs as well as the possibility of fetal loss caused by invasive procedures can be reduced. Other potentially useful sonographic markers need further studies, although previous preliminary research suggests their usefulness. This article will review those sonographic markers.

Prenatal control of Hb Bart's disease in mainland China: can we do better?

The aim of the present study was to report a 3-year experience on the prenatal control of Hb Bart's (γ4) disease in Mainland China. All pregnancies with fetal Hb Bart's disease were included from January 2011 to December 2013. The main clinical characteristics of the affected pregnancies were reviewed, including maternal reproductive history, prenatal care in the current pregnancy, the gestation of pregnancy at the time of booking, the gestation at the time of prenatal diagnosis (PND), and the complications associated with the pregnancy. A total of 246 cases of fetal Hb Bart's disease were identified during the study period; among these, 177 (72.0%) were diagnosed in early gestation (≤24 weeks), and 69 (28.0%) in late gestation. Most (87.0%) of the patients presenting in late pregnancy had late or no prenatal care. Twenty (29.0%) had major obstetrical complications in patients presenting in late pregnancy, and five (5.0%) in patients presenting in relatively early pregnancy. The delay in PND deprived couples of opportunities to make informed decisions early in pregnancy. Efforts for designing and targeting strategies to improve the timeliness of prenatal care are urgently needed.

Hemoglobin α in the blood vessel wall

Hemoglobin has been studied and well characterized in red blood cells for over 100 years. However, new work has indicated that the hemoglobin α subunit (Hbα) is also found within the blood vessel wall, where it appears to localize at the myoendothelial junction (MEJ) and plays a role in regulating nitric oxide (NO) signaling between endothelium and smooth muscle. This discovery has created a new paradigm for the control of endothelial nitric oxide synthase activity, nitric oxide diffusion, and, ultimately, vascular tone and blood pressure. This review discusses the current knowledge of hemoglobin׳s properties as a gas exchange molecule in the bloodstream and extrapolates the properties of Hbα biology to the MEJ signaling domain. Specifically, we propose that Hbα is present at the MEJ to regulate NO release and diffusion in a restricted physical space, which would have powerful implications for the regulation of blood flow in peripheral resistance arteries.

Prenatal control of Hb Bart's hydrops fetalis: a two-year experience at a mainland Chinese hospital

α-Thalassemia is a common inherited disease in southern China. The severest form is Hb Bart's hydrops fetalis, in which the affected fetuses almost always die in utero or shortly after birth, and the mothers are at high risk for severe morbidity. Therefore, this condition should be controlled, especially prenatally. In this study, we reported on a two-year experience in prenatal control of Hb Bart's hydrops fetalis at a mainland Chinese hospital. Totally, 573 pregnancies at risk for Hb Bart's hydrops fetalis were referred and different prenatal procedures were offered depending on the gestational age at presentation. One hundred fifty-two affected fetuses were diagnosed prenatally; among these, only half presented in early gestation, and were terminated in time. Although our prenatal program has successfully prevented the birth of children with severe thalassemia, it does not show a satisfactory outcome, considering the gestational age when an affected pregnancy is terminated.

Two unusual cases of haemoglobin Bart's hydrops fetalis due to uniparental disomy or non-paternity

The authors present 2 unusual cases of haemoglobin (Hb) Bart's hydrops fetalis and highlight the problem of a screening system for α-thalassaemia which focuses on maternal and paternal mean corpuscular volume (MCV) alone. Normal paternal MCV may not preclude fetal Hb Bart's disease because of the rare occurrence of maternal uniparental disomy or non-paternity. During a mid-trimester anomaly scan, with fetal cardiomegaly or hydrops in a woman with low MCV but normal paternal MCV, obstetricians should remain alert for fetal Hb Bart's disease. This is very important and relevant for national screening systems in South-East Asia, where a routine mid-trimester scan may not be available. A routine mid-trimester anomaly scan should therefore be implemented and in high prevalence areas, sonographers should be sensitive to the cardio-thoracic ratio even if screening shows that pregnancy is unlikely to be at risk.

In Utero diagnosis and management of a fetus with homozygous α-Thalassemia in the second trimester: a case report and literature review

Alpha thalassemia with the absence of 4 α-globin genes leads to fetal hydrops and fetal death from anemia. Historically considered a lethal condition, optimal in utero management of homozygous α-thalassemia is unclear. A fetus of Filipino descent at 26 weeks gestation presented with ultrasound evidence of anemia. Cordocentesis confirmed anemia and homozygous α-thalassemia (--/--). Intrauterine transfusion corrected anemia but fetal growth restriction and oligohydramnios persisted. Intrauterine exchange transfusion improved hemoglobin parameters, fetal growth, and oligohydramnios. The late preterm infant was delivered with classic limb reduction defects. Hemoglobin Bart's is nonfunctional for oxygen transport, and intrauterine exchange transfusion may be effective first-line therapy and further investigation is warranted.

Splenic circumference at midpregnancy as a predictor of hemoglobin Bart's disease among fetuses at risk

OBJECTIVE

To determine the accuracy of splenic circumference in predicting hemoglobin (Hb) Bart's disease among fetuses at risk at midpregnancy.

MATERIALS AND METHODS

Women with singleton pregnancies with a fetal risk of Hb Bart's disease were enrolled in the study at 18-22 weeks of gestation. All underwent splenic circumference measurement before cordocentesis for fetal blood analysis. The final diagnosis used as a gold standard was based on fetal Hb typing using high-performance liquid chromatography.

RESULTS

Among all the pregnancies, the prevalence of Hb Bart's disease was 26.1% (87/334 fetuses). Twenty-four fetuses (27.6%) had some degree of hydropic changes. Notably, of these 24, 22 showed splenomegaly as well. When hydropic fetuses were excluded, the sensitivity, specificity, positive predictive value and negative predictive value of splenic circumference in identifying affected fetuses were 68.3, 83.0, 50.6 and 91.1%, respectively.

CONCLUSION

Splenic circumference measurement at midpregnancy may be helpful in distinguishing affected fetuses from those unaffected. Among couples at risk with normal splenic size, the risk of having an affected child is much lower, whereas the enlarged spleen places the pregnancy at a higher risk. This information may help couples decide on invasive diagnosis or a noninvasive approach.

Fetal liver length measurement at mid-pregnancy among fetuses at risk as a predictor of hemoglobin Bart's disease

OBJECTIVE

To assess the effectiveness of liver length measurement in predicting hemoglobin (Hb) Bart's disease among fetuses at risk at mid-pregnancy.

STUDY DESIGN

Pregnant women at risk of fetal Hb Bart's disease at 18 to 22 weeks of gestation were enrolled in the study. All of them underwent liver length measurement just before cordocentesis for fetal blood analysis. The final diagnosis used as a gold standard was based on fetal Hb typing using high-performance liquid chromatography.

RESULT

A total of 334 pregnant women were recruited into the study. The prevalence of fetal Hb Bart's disease was 26.1% (87 of 334 fetuses). The sensitivity, specificity, as well as positive and negative predictive values of liver length in the prediction of affected fetuses were 71.3, 95.5, 84.9 and 90.4%, respectively. Overall, 24 fetuses (27.6%) had some degree of early hydrops fetalis. Of these, 20 had hepatomegaly as well.

CONCLUSION

Liver length measurements at mid-pregnancy may be helpful in predicting affected fetuses among pregnancies at risk. Normal liver length measurement is associated with a very low risk of the disease. This information may help couples decide on whether to opt for either invasive diagnosis or a noninvasive approach, especially when used as an adjunct to other tests.

Causes and consequences of 93 fetuses with cardiomegaly in a tertiary center in Thailand

OBJECTIVES

To assess etiology, perinatal mortality and associated factors of fetal cardiomegaly (FC).

METHODS

A retrospective study of fetuses with cardiomegaly was conducted. Demographic data, ultrasonographic findings, and outcomes were collected and analyzed.

RESULTS

Ninety-three fetuses were analyzed. The causes of FC were cardiac causes 49.5%, Bart's hemoglobinopathies 28%, and non-Bart's anemia 15%. Ascites, pericardial effusion, and hydrops were more prevalent in fetuses with anemia than those with cardiac abnormalities. The overall perinatal mortality was 69.9%. Although all Bart's hydrops died, perinatal mortality of non-Bart's anemia, and structural cardiac defect were 57.1 and 69.7%, respectively. Excluding Bart's anemia, receiver-operating characteristic curve analysis demonstrated that cardiothoracic ratio of ≥0.58 best predictive for perinatal mortality. Earlier gestational age at diagnosis, skin edema, and chromosomal abnormality were associated with higher mortality.

CONCLUSIONS

Majority causes of FC were cardiac and anemic in origin. It carried high-perinatal mortality depending on the causes.

Ultrasonographic prediction of homozygous alpha0-thalassemia using placental thickness, fetal cardiothoracic ratio and middle cerebral artery Doppler: alone or in combination?

OBJECTIVE

To compare the predictive values of three ultrasonographic parameters: placental thickness (PT), fetal cardiothoracic ratio (CTR) and middle cerebral artery peak systolic velocity (MCA-PSV), alone or in combination, in pregnancies affected by homozygous alpha(0)-thalassemia at 12-20 weeks' gestation.

METHODS

Pregnant women at risk of carrying a fetus affected by homozygous alpha(0)-thalassemia were studied from 1995 to 2006 using serial ultrasonography at 12-15 weeks, 16-20 weeks and 30 weeks' gestation. We measured CTR and PT from 1995, and MCA-PSV as well from 1997. An invasive prenatal test was offered if cardiomegaly with or without placentomegaly was detected but the MCA-PSV results were used only retrospectively for analysis.

RESULTS

Of a total of 777 at-risk fetuses studied, 138 (17.8%) were affected by homozygous alpha(0)-thalassemia. At 12-15 weeks' gestation, 598 ultrasound examinations were performed. CTR was better than both PT and MCA-PSV in the prediction of affected pregnancies. The highest sensitivity (98.3%) was achieved by the combination of CTR and/or MCA-PSV at a false-positive rate of 15.8%. At 16-20 weeks' gestation, 410 ultrasound examinations were performed, 121 of which were at the patient's first visit and 289 of which were at a follow-up visit. Both CTR and MCA-PSV predicted the affected pregnancies equally well. The sensitivity of CTR was 100.0%, but the false-positive rate was 5.2%. In contrast, the false-positive rate of MCA-PSV alone was 1.4% and that of the combination of CTR and MCA-PSV was 0%, although their sensitivities were less than 65%.

CONCLUSIONS

The data suggest that adding MCA-PSV to CTR in the prediction of homozygous alpha(0)-thalassemia can increase the sensitivity at 12-15 weeks and decrease the false-positive rate at 16-20 weeks' gestation.

[Major alpha-thalassemia: antenatal diagnosis, case report and literature review]

Homozygous alpha-thalassaemia or Bart's hydrops fetalis is a genetic disease with autosomal recessive transmission. The condition is lethal for the fetus because of hypoxia and anemia. For the mother there is an increased risk of the severe forms of preeclampsia and its complications. The diagnosis can be suspected in presence of suggestive ultrasonographic anomalies, where both parents come from South-East Asia or China. Confirmation is based on the identification of the typical deletions or mutation of the alpha globin gene by molecular genetics. We report a rare clinical case of Bart's hydrops fetalis diagnosed because of fetal growth retardation, fetal cardiomegaly and increased size of placenta on the 26 weeks fetal echography. This case underscores the need to include the alpha thalassemias in medical and midwifery education in countries where they were almost inexistent a generation ago.

Alpha-thalassaemia

Alpha-thalassaemia is one of the most common human genetic disorders. Couples in which both partners carry alpha(0)-thalassaemia traits have a 25% risk of having a fetus affected by homozygous alpha-thalassaemia or haemoglobin Bart's disease, with severe fetal anaemia in utero, hydrops fetalis, stillbirth or early neonatal death, as well as causing various maternal morbidities. This disorder is common in southeast Asia and southern China, and the expanding populations of southeast Asian immigrants in the US, Canada, UK and Europe mean that this disorder is no longer rare in these countries.

Comparison of nuchal and detailed morphology ultrasound examinations in early pregnancy for fetal structural abnormality screening: a randomized controlled trial

OBJECTIVE

To compare the effectiveness of a nuchal scan at 10 to 14 + 6 weeks and a detailed morphology scan at 12 to 14 + 6 weeks in screening for fetal structural abnormalities.

METHODS

From March 2001 to November 2004, 8811 pregnant women were randomized into either the control group (10 to 14 + 6-week nuchal scan followed by routine 16-23-week scan) or the study group (10 to 14 + 6-week nuchal scan and 12 to 14 + 6-week detailed scan followed by routine 16-23-week scan).

RESULTS

We analyzed 7642 cases of singleton pregnancies with viable fetuses at first-trimester ultrasound examination and with known pregnancy outcome. In the control group, the detection rate of structural abnormalities in the first trimester was 32.8% (21/64; 95% CI, 21.6-45.7%) and the overall detection rate was 64.1% (41/64; 95% CI, 51.1-75.7%). In the study group, the detection rate in the first trimester was 47.6% (30/63; 95% CI, 34.9-60.6) and the overall detection rate was 66.7% (42/63; 95% CI, 53.7-78.0%). The overall detection rate in the control group did not differ significantly from that in the study group (P > 0.05).

CONCLUSIONS

When the nuchal scan is offered, a basic anatomical survey can be done in conjunction with nuchal translucency thickness measurement. A detailed ultrasound examination at this early gestational age may not be superior to the nuchal scan in screening for fetal abnormalities in the low-risk population. Though a wide range of abnormalities can be detected at 10 to 14 + 6 weeks, the routine 16-23-week scan cannot be abandoned.