Prenatal sonographic assessment of the fetal thorax: normal values

Value of fetal echocardiographic examination in pregnancies complicated by preterm premature rupture of membranes

OBJECTIVES

Cardiopulmonary and infectious complications are more common in preterm newborns after preterm premature rupture of membranes (pPROM). Fetal echocardiography may be helpful in predicting neonatal condition. Our aim was to assess the cardiovascular changes in fetuses from pregnancies complicated by pPROM and possible utility in predicting the intrauterine or neonatal infection, and neonatal heart failure (HF).

METHODS

It was a prospective study enrolling 46 women with singleton pregnancies complicated by pPROM between 18+0 and 33+6 weeks of gestation and followed until delivery. 46 women with uncomplicated pregnancies served as a control group. Fetal echocardiographic examinations with the assessment of cardiac structure and function (including pulmonary circulation) were performed in all patients.

RESULTS

Mean gestational age of pPROM patients was 26 weeks. Parameters suggesting impaired cardiac function in fetuses from pPROM were: higher right ventricle Tei index (0.48 vs. 0.42 p<0.001), lower blood flow velocity in Ao z-score (0.14 vs. 0.84 p=0.005), lower cardiovascular profile score (CVPS), higher rate of tricuspid regurgitation (18.2 % vs. 4.4 % p=0.04) and pericardial effusion (32.6 vs. 0 %). Intrauterine infection was diagnosed in 18 patients (39 %). 4 (8.7 %) newborns met the criteria of early onset sepsis (EOS). HF was diagnosed in 9 newborns. In fetal echocardiographic examination HF group had shorter mitral valve inflow time and higher left ventricle Tei index (0.58 vs. 0.49 p=0.007).

CONCLUSIONS

Worse cardiac function was observed in fetuses from pPROM compared to fetuses from uncomplicated pregnancies.

Foetal thoracic hypoplasia: concomitant anomalies and neonatal outcomes

The aim of the current study was to determine the frequency of concomitant anomalies in foetal thoracic hypoplasia and the neonatal outcomes of these pregnancies. This retrospective study included 49 cases of foetal thoracic hypoplasia. All of the cases had skeletal system anomalies. Head and face anomalies (36.7%) were the second most frequent accompanying foetal anomaly, and the least common anomaly was genital system anomalies (4.1%). During the follow-ups, 52.6% (n = 10) of the newborns died in the first 24 h of life, 10.5% (n = 2) in the neonatal period and 36.8% (n = 7) in the infantile period.IMPACT STATEMENTWhat is already known on this subject? Foetal thoracic hypoplasias are lethal anomalies due to inadequate pulmonary development. Data on the other system anomalies that accompany foetuses with thoracic hypoplasia are quite limited in the literature. Moreover, even if the lethal course of thoracic hypoplasia is known, the information on how long newborns will survive is unclear.What do the results of this study add? In this study, most of the cases have additional anomalies, especially skeletal system and head-face anomalies. Approximately half of the newborns with thoracic hypoplasia die within the first 24 h.What are the implications of these findings for clinical practice and/or further research? When we need to consult a family considering the outcome of thoracic hypoplasia, this study can be guiding and helpful. On the other hand, the effects of additional anomalies on the prognosis of foetal and neonatal period are not clear. More studies are needed to better understand the prognosis of thoracic hypoplasias.

Current Overview of Osteogenesis Imperfecta

Osteogenesis imperfecta (OI), or brittle bone disease, is a heterogeneous disorder characterised by bone fragility, multiple fractures, bone deformity, and short stature. OI is a heterogeneous disorder primarily caused by mutations in the genes involved in the production of type 1 collagen. Severe OI is perinatally lethal, while mild OI can sometimes not be recognised until adulthood. Severe or lethal OI can usually be diagnosed using antenatal ultrasound and confirmed by various imaging modalities and genetic testing. The combination of imaging parameters obtained by ultrasound, computed tomography (CT), and magnetic resource imaging (MRI) can not only detect OI accurately but also predict lethality before birth. Moreover, genetic testing, either noninvasive or invasive, can further confirm the diagnosis prenatally. Early and precise diagnoses provide parents with more time to decide on reproductive options. The currently available postnatal treatments for OI are not curative, and individuals with severe OI suffer multiple fractures and bone deformities throughout their lives. In utero mesenchymal stem cell transplantation has been drawing attention as a promising therapy for severe OI, and a clinical trial to assess the safety and efficacy of cell therapy is currently ongoing. In the future, early diagnosis followed by in utero stem cell transplantation should be adopted as a new therapeutic option for severe OI.

Radiation exposure by digital radiographic imaging in very low birth weight infants

OBJECTIVE

The aim of this study was to determine the cumulative effective doses (CED) from digital radiographic imaging in very low birth weight infants treated in a tertiary care neonatal intensive care unit (NICU).

STUDY DESIGN

The CED for each infant was retrospectively calculated using a voxel-based model. The results were compared with previous studies applying conventional radiography.

RESULTS

Two hundred and six preterm infants were included into this study. Neonates received a median of four radiographs (range: 1-68) and a CED of 50 µSv (4-883 µSv). Overall mean CED was lower than in previously published data applying conventional radiography. Factors contributing to a lower radiation dose per infant in our study were a lower number of radiographs and smaller field sizes per radiographic image.

CONCLUSIONS

The number of conducted radiographs per patient and the employed field size had a higher impact on the CED than the applied radiographic technology.

Fetal-MRI prenatal diagnosis of severe bilateral lung hypoplasia: alveolar capillary dysplasia case report

Alveolar capillary dysplasia with misalignment of pulmonary veins (ACD/MPV) is a rare and lethal developmental disorder of the lung that affect both acinar structure and the intrinsic pulmonary vasculature. We report prenatal and postnatal imaging with histopathological findings of this rare condition. We, first, describe MR imaging features and discuss its role in prenatal imaging.

Normal Fetal Growth Assessment: A Review of Literature and Current Practice

A review of literature and current practice of normal fetal growth assessment is presented. Ultrasonographic dating of pregnancy in the first, second, and third trimester is reviewed. Individual biometric parameters are examined, and the proper use of the fetal growth profile is explained. Use of this information is discussed as it pertains to the single pregnancy.

Sonographic Detection of Skeletal Dysplasia

A case of skeletal dysplasia was sonographically evaluated in the fetus of a 21-year-old patient. The diagnosis of osteogenesis imperfecta type II was suggested during a routine morphological examination at 17 weeks’ gestation, based on visualization of rhizomelia, bowed long bones, and decreased thoracic cavity size. Sonographically, this dysplasia was well visualized and contributed to a final diagnosis, highlighting the diagnostic value of prenatal sonography. The use of routine sonographic examinations continues to prove crucial for early detection of fetal abnormalities such as skeletal dysplasias.

Prediction of lethal pulmonary hypoplasia by means fetal lung volume in skeletal dysplasias: a three-dimensional ultrasound assessment

OBJECTIVE

The aim of this study was to assess the capacity of three-dimensional ultrasound (3DUS) for predicting lethality in fetuses with skeletal dysplasia.

METHODS

Twenty-four fetuses between 20 and 32 weeks of gestation were assessed. Bilateral lung volume scans were performed three times in each fetus during one ultrasound session. The virtual organ computer-aided analysis method was used to obtain a sequence of six sections of each lung around a fixed axis, and a rotation angle of 30° was adopted. Fetal lung volume measurements were analyzed according to the reference range. After birth, lung hypoplasia was diagnosed considering clinical and radiological criteria.

RESULTS

Of all cases of skeletal dysplasia, 18 (75%) were lethal. Among the lethal cases, after postnatal diagnosis, four were osteogenesis imperfecta type II, three were thanatophoric dysplasia and two were campomelic dysplasia. The remaining nine cases remained without a definitive diagnosis. The accuracy of 3DUS in predicting lethality in fetuses with skeletal dysplasia was high, with a sensitivity of 83.3%, specificity of 100%, positive predictive value of 100% and negative predictive value of 66.7%. The kappa index of 0.174 showed a good agreement between the possibility of lethality when the 3DUS volume measurement was altered and real lethality after birth (p < 0.001).

CONCLUSION

This study suggests that the 3DUS lung volume measurement is a good predictor of lethal pulmonary hypoplasia in fetuses with skeletal dysplasia, with high accuracy.

Fetal skeletal dysplasias: sonographic indices associated with adverse outcomes

OBJECTIVES

To assess the utility of biometric indices and amniotic fluid volume in identifying fetuses with lethal skeletal dysplasia.

METHODS

A review of pregnancies with sonographic diagnosis of skeletal dysplasia between January 1997 and March 2012 from a single institution was conducted. Biometric indices and amniotic fluid volumes were reviewed from the initial targeted sonograms and all subsequent examinations. Outcomes were verified in all cases. Pregnancies that resulted in fetal or neonatal death were considered to have lethal dysplasia, and those with survival to hospital discharge were considered to have nonlethal dysplasia.

RESULTS

Of 45 fetuses with suspected skeletal dysplasia, 27 (60%) survived to hospital discharge; 9 (20%) died in the immediate neonatal period; 2 (4%) resulted in stillbirth; and in 7 cases (16%), pregnancy termination was elected. Those with lethal dysplasia were more likely to have hydramnios on initial detection than those who survived to hospital discharge (83% versus 27%; P < .01). Pregnancies complicated by lethal skeletal dysplasia had a significantly lower femur length-to-abdominal circumference ratio and were more likely to have a ratio below 0.16 than those with neonatal survival (91% versus 11%; P < 0.01). The lowest femur length-to-abdominal circumference ratio and the proportion with a ratio below 0.16 at any point in gestation were significantly different between those with lethal and nonlethal dysplasia (P< .01). As fetal size increased with advancing gestation, the relationship of sonographic parameters (eg, femur length-to-abdominal circumference ratio) became more pronounced. There was no infant survival when hydramnios was encountered at any point during gestation in the setting of a femur length-to-abdominal circumference ratio below 0.16.

CONCLUSIONS

In our series, a femur length-to-abdominal circumference ratio below 0.16 in conjunction with hydramnios effectively identified fetuses with lethal skeletal dysplasia.

FGFR3 related skeletal dysplasias diagnosed prenatally by ultrasonography and molecular analysis: presentation of 17 cases

Fibroblast Growth Factor Receptor 3 (FGFR3) related skeletal dysplasias are caused by mutations in the FGFR3 gene that result in increased activation of the receptors causing alterations in the process of endochondral ossification in all long bones, and include achondroplasia, hypochondroplasia, thanatophoric dysplasia, and SADDAN. Reports of prenatal diagnosis of FGFR3 related skeletal dysplasias are not rare; however, the correlation between 2nd trimester ultrasonographic findings and underlying molecular defect in these cases is relatively poor. There is a need for specific ultrasound (U/S) predictors than can distinguish lethal from non-lethal cases and aid an earlier prenatal diagnosis. Here we present one familial and 16 sporadic cases with FGFR3 related skeletal dysplasia, and we evaluate biometric parameters and U/S findings consistent with the diagnosis of skeletal dysplasia. U/S scan performed even at the 18th week of gestation can indicate a decreased rate of development of the femora (femur length (FL) <5th centile), while the mean gestational age at diagnosis is still around the 26th week. The utility of other biometric parameters and ratios is discussed (foot length, BPD, HC, FL/foot, and FL/AC). Prenatal cytogenetic and molecular genetic analyses were performed. A final diagnosis was reached by molecular analysis. In two cases of discontinued pregnancy, fetal autopsy led to a phenotypic diagnosis and confirmed the prenatal prediction of lethality. We conclude that the combination of U/S and molecular genetic approach is helpful for establishing an accurate diagnosis of FGFR3-related skeletal dysplasias in utero and subsequently for appropriate genetic counselling and perinatal management.

Three-dimensional ultrasound fetal lung volumes and infant respiratory outcome: a prospective observational study

OBJECTIVE

To determine if fetal lung volumes (FLVs), determined by three-dimensional rotational ultrasound and virtual organ computer-aided analysis software (vocal), correlated with neonatal respiratory outcomes in surviving infants who had a high risk [fetuses with congenital diaphragmatic hernia (CDH)], lower risk [fetuses with anterior wall defects (AWDs)] and no risk (controls) of abnormal antenatal lung growth.

DESIGN

Prospective observational study.

SETTING

Tertiary fetal medicine and neonatal intensive care units.

POPULATION

Sixty fetuses (25 with CDH, 25 with AWDs and ten controls).

METHODS

FLVs were measured and expressed as the percentage of the observed compared with the expected for gestational age.

MAIN OUTCOME MEASURES

Neonatal respiratory outcome was determined by the duration of supplemental oxygen, mechanical ventilation and dependencies, and assessment of lung volume using a gas dilution technique to measure functional residual capacity (FRC).

RESULTS

The infants with CDH had lower FLV results than both the infants with AWDs (P=0.05) and the controls (P<0.05). The infants with CDH had longer durations of mechanical ventilation (P<0.001) and supplementary oxygen (P<0.001) dependence, compared with infants with AWDs. The infants with CDH had a lower median FRC than both the infants with AWDs (P<0.001) and the controls (P<0.001). FLV results correlated significantly with the durations of dependency on ventilation (r= -0.744, P<0.01) and oxygen (r= -0.788, P<0.001), and with FRC results (r=0.429, P=0.001).

CONCLUSIONS

These results suggest that FLVs obtained using three-dimensional rotational ultrasound might be useful in predicting neonatal respiratory outcome in surviving infants who had varying risks of abnormal lung growth. Larger and more comprehensive studies are needed to clarify the role that lung volume measurements have in assessing lung function and growth.

Phenotype of five cases of prenatally diagnosed campomelic dysplasia harboring novel mutations of the SOX9 gene

OBJECTIVES

Campomelic dysplasia is a rare congenital skeletal disorder characterized by bowing of the long bones and a variety of other skeletal and extraskeletal defects, many of which can now be identified prenatally using advanced ultrasound equipment. The disorder is caused by mutations in SRY-box 9 (SOX9), a gene that is abundantly expressed in chondrocytes as well as in other tissues. However, the correlation between genotype and phenotype is still unclear. We report five cases of prenatally detected campomelic dysplasia in which the diagnosis was confirmed by molecular analysis.

METHODS

Ultrasound examinations were performed between 12 and 32 weeks. Standard fetal biometric measurements were obtained. Fetal sex was determined sonographically and confirmed by chromosomal analysis. Genomic DNA was obtained in four cases before termination of pregnancy from chorionic villi or amniocytes and in one case postnatally from peripheral blood.

RESULTS

Skeletal dysplasia, most often limb shortening and bowed femora, was observed in one case in the first trimester, in three cases in the second trimester and in one case, presenting late for antenatal care, in the third trimester. Four of the pregnancies were terminated and one was carried to term. Postmortem/postnatal physical and radiographic examinations confirmed the presence of anomalies characteristic of campomelic dysplasia. A de novo mutation in the SOX9 gene was detected in all four cases that underwent termination. The father of the proband in the case that went to term was a carrier of a somatic mosaic mutation without clinical or radiographic signs of campomelic dysplasia.

CONCLUSIONS

It is likely that the integrated expertise of ultrasonographers, obstetricians, pediatricians and clinical geneticists will markedly improve the likelihood of accurate prenatal clinical diagnoses of campomelic dysplasia. This will, in turn, encourage more specific molecular testing and facilitate comprehensive genetic counseling.

[Asphyxiating thoracic dysplasia (Jeune syndrome): about two cases]

Asphyxiating thoracic dysplasia (Jeune syndrome) is an osteochondrodysplasia with autosomal recessive inheritance, characterised by a nanism with rhizomelic predominance, associated with a narrow thorax. It induces an alteration of the respiratory function that conditions the prognosis, which is worsened in case of associated visceral lesions (probably related to mutations of genes implicated in ciliary development, as recently described). We report the observation of two severe cases of Jeune syndrome to emphasize the advancement of imaging, especially echography, and molecular biology in establishing prenatal diagnosis as well as prognosis of this syndrome.

Oligohydramnios and associated fetal complications

During intrauterine life the fetus is bathed in amniotic fluid which provides a low resistance space for free movement and a buffer against external trauma. This fluid is produced in early pregnancy largely as a maternal dialysate, then as a fetal transudate. Fetal urine is the most important source of amniotic fluid after 16 weeks gestation. The control of amniotic fluid is complex and poorly understood; it arises from secondary partitioning of water within the fetoplacental extracellular space and reflects fetal fluid balance.

Fetal skeletal dysplasia: an approach to diagnosis with illustrative cases

Skeletal dysplasias are a heterogeneous group of conditions associated with various abnormalities of the skeleton. These conditions are caused by widespread disturbance of bone growth, beginning during the early stages of fetal development and evolving throughout life. Despite recent advances in imaging, fetal skeletal dysplasias are difficult to diagnose in utero due to a number of factors, including the large number of skeletal dysplasias and their phenotypic variability with overlapping features, lack of precise molecular diagnosis for many disorders, lack of a systematic approach, the inability of ultrasonography (US) to provide an integrated view, and variability in the time at which findings manifest in some skeletal dysplasias. US of suspected skeletal dysplasia involves systematic imaging of the long bones, thorax, hands and feet, skull, spine, and pelvis. Assessment of the fetus with three-dimensional US has been shown to improve diagnostic accuracy, since additional phenotypic features not detectable at two-dimensional US may be identified. The radiologist plays a major role in making an accurate diagnosis; however, representatives of other disciplines, including clinicians, molecular biologists, and pathologists, can also provide important diagnostic information.

Utility of cardiac monitoring in fetuses at risk for congenital heart block: the PR Interval and Dexamethasone Evaluation (PRIDE) prospective study

BACKGROUND

Anti-SSA/Ro-associated third-degree congenital heart block is irreversible, prompting a search for early markers and effective therapy.

METHODS AND RESULTS

One hundred twenty-seven pregnant women with anti-SSA/Ro antibodies were enrolled; 95 completed an evaluable course in 98 pregnancies. The protocol included fetal echocardiograms performed weekly from 16 to 26 weeks' gestation and biweekly from 26 to 34 weeks. PR intervals >150 ms were considered prolonged, consistent with first-degree block. Ninety-two fetuses had normal PR intervals. Neonatal lupus developed in 10 cases; 4 were neonatal lupus rash only. Three fetuses had third-degree block; none had a preceding abnormal PR interval, although in 2 fetuses >1 week elapsed between echocardiographic evaluations. Tricuspid regurgitation preceded third-degree block in 1 fetus, and an atrial echodensity preceded block in a second. Two fetuses had PR intervals >150 ms. Both were detected at or before 22 weeks, and each reversed within 1 week with 4 mg dexamethasone. The ECG of 1 additional newborn revealed a prolonged PR interval persistent at 3 years despite normal intervals throughout gestation. No first-degree block developed after a normal ECG at birth. Heart block occurred in 3 of 16 pregnancies (19%) in mothers with a previous child with congenital heart block and in 3 of 74 pregnancies (4%) in mothers without a previous child with congenital heart block or rash (P=0.067).

CONCLUSIONS

Prolongation of the PR interval was uncommon and did not precede more advanced block. There was a trend toward more congenital heart block in fetuses of women with previously affected offspring than those without previously affected offspring. Advanced block and cardiomyopathy can occur within 1 week of a normal echocardiogram without initial first-degree block. Echodensities and moderate/severe tricuspid regurgitation merit attention as early signs of injury.

Reliability of the lung-to-head ratio as a predictor of outcome in fetuses with isolated left congenital diaphragmatic hernia at gestation outside 24-26 weeks

OBJECTIVE

The purpose of this study was to investigate the relationship between lung-to-head ratio (LHR) and gestational age (GA) in fetuses with isolated left congenital diaphragmatic hernia and to determine the applicability and reliability of LHR to predict postnatal outcome beyond 24-26 weeks of gestation.

STUDY DESIGN

The institutional review board approved this retrospective review of the University of California, San Francisco, Fetal Treatment Center database for cases with left congenital diaphragmatic hernia who were referred between March 1995 and June 2004. LHR was determined at the initial evaluation. One hundred seven live-born fetuses at 20-34 weeks of gestation (excluding cases that were lost to follow-up, with factors that potentially could influence the LHR measurement or postnatal outcome, or that were terminated electively).

RESULTS

The median GA at LHR measurement was 25.6 weeks; the median LHR was 1.01; the median GA at birth was 37.7 weeks; and the overall survival rate was 59% (64/107). The median LHR of nonsurvivors was significantly lower than that of survivors, but neither GA at LHR measurement nor at delivery was significantly different between the groups. Multiple logistic regression analysis confirmed LHR to be an independent predictor of postnatal survival, and receiver-operator characteristic curve analysis demonstrated that an LHR of > or = 0.97 has the highest performance in predicting postnatal survival. When fetuses were grouped by GA at initial LHR measurement to determine reliability of LHR, specifically with respect to GA, in the 26-34 and 24-26 weeks of gestation groups, median LHR of survivors was significantly higher than that of nonsurvivors, and receiver-operator characteristic curve analysis confirmed LHR to be a reliable predictor of postnatal survival. However, for fetuses at 20-24 weeks of gestation, there was a trend toward a higher LHR in survivors, although this did not reach statistical significance.

CONCLUSION

A significant positive linear relationship exists between LHR and GA at the time of measurement, such that LHR reliably predicts postnatal survival in fetuses with left congenital diaphragmatic hernia at 24-34 weeks of gestation and less reliable at 20-24 weeks. However, given the limitations of a retrospective, cross-sectional study, further prospective longitudinal studies that will investigate the change of LHR with GA and its association with fetal outcome are necessary.

Fetal Posterior Fossa Volume: Assessment with MR Imaging

PURPOSE

To retrospectively determine the relationship between posterior fossa volume (PFV) and estimated gestational age (EGA) and/or femur length (FL) during pregnancy for the purpose of developing a normal growth curve.

MATERIALS AND METHODS

Advance institutional review board approval was obtained for this HIPAA-compliant study, and the need for parent informed consent was waived. A cross-sectional retrospective study was performed to measure PFV on in vivo magnetic resonance (MR) images obtained in 76 fetuses of 18-36 weeks gestation who had a morphologically normal CNS. Because this was a retrospective series, MR imaging techniques varied slightly, but all fetuses underwent imaging at contiguous 3-5-mm intervals in at least two orthogonal planes, with repetition time msec/echo time msec, 5-12/62-95; number of signals acquired, one; flip angle, 150 degrees -180 degrees; and matrix, 128-192 x 256. Posterior fossa areas were manually traced on half-Fourier rapid acquisition with relaxation enhancement in utero fetal MR images by one observer. PFVs were then calculated by manually summing areas from the contiguous sections and multiplying the total area by the section thickness. An average PFV (APFV) across orthogonal planes was calculated for each fetus, and the relationship between APFV and EGA was mathematically modeled. Coronal, transverse, and sagittal views were compared with correlations and Bland-Altman plots. Two additional observers repeated the measurements for a small subset of fetuses (n = 5). Paired t test analyses were also performed to determine significant differences between sagittal, transverse, and coronal measurements, as well as to determine preliminary intraobserver and interobserver variability of measurements in a subset of cases.

RESULTS

The relationship between APFV (in cubic centimeters) and EGA (in weeks) was well described by a single exponential function [APFV = 0.689 exp(EGA/9.10)]. APFV doubling time was 6.31 weeks. Root-mean-square variation of values around the model line was 1.63 cm(3). There was no statistically significant intra- or interobserver variation (P > .16 for all fetuses) at preliminary analysis. No correlation between APFV and FL could be found.

CONCLUSION

The normal fetal PFV growth curve generated in this study may have potential as a model for clinical application.

Combined Prenatal Ultrasound and Magnetic Resonance Imaging in an Extensive Congenital Fibrosarcoma: A Case Report and Review of the Literature

OBJECTIVE

Tumors of congenital origin differ in their symptoms and signs, predominant location and prognosis from those occurred later in childhood. To determine whether the prognosis of congenital (infantile) fibrosarcoma in the retroperitoneum, an extremely rare form of soft tissue malignant tumor, can be assessed prenatally.

METHODS

We describe a case of this condition diagnosed in utero, including the assessment of the tumor behavior by ultrasound and magnetic resonance imaging. We also review the English language literature in Medline over the past 10 years and describe the management options available in such cases.

RESULTS

Our case had precise prenatal findings revealed unfavorable conditions such as bulky tumor mass, spinal metastasis and pulmonary hypoplasia.

CONCLUSION

Fetal imaging studies could accurately identify the invasion of tumor. The outcome is usually poor, especially for those fetuses affected by an axial location of the tumor.

Fetal lung volumetry using two- and three-dimensional ultrasound

OBJECTIVES

To compare methods of measuring fetal pulmonary volume and to establish nomograms of fetal pulmonary volume according to gestational age for the accurate diagnosis of pulmonary hypoplasia.

METHODS

Three methods of measuring fetal pulmonary volume in 39 normal fetuses were compared: two-dimensional (2D) ultrasound measurement assuming that the lung is a geometrical pyramid, three-dimensional (3D) ultrasound using the VOCAL rotational method, and the conventional multiplanar 3D mode. Linear regression was used to construct an equation for 3D volume calculation from 2D measurements (the re-evaluated pulmonary volume equation (RPVE)). Lung volume measurements were recorded from 622 singleton fetuses in order to construct nomograms.

RESULTS

There was no statistically significant difference between the lung volume values obtained using the two 3D modes. However, in comparison with the 2D measurements the volumes obtained were larger (mean difference = 11.99, P < 0.1 x 10(-6)). The relationship between the 2D and 3D volumes was determined using a statistical linear regression method: RPVE (mL) = 4.24 + (1.53 x 2DGPV), where 2DGPV (2D geometric pulmonary volume) = (surface area right lung base (cm2) + surface area left lung base (cm2)) x 1/3 height right lung (cm). Two nomograms were constructed, one for use with 2D and one for 3D technology.

CONCLUSION

2D pulmonary volume assessment can be used in clinical situations where fetal prognosis depends on lung volume and its growth potential. It is routinely available and easy to perform particularly when repeat measurements are required in evaluation of lung growth. We therefore propose this method as an alternative to magnetic resonance imaging or 3D ultrasound.

Fetal thoracic measurements in prenatal diagnosis of Jeune syndrome

We describe prenatal sonographic findings in a 34-week fetus with Jeune syndrome or asphyxiating thoracic dystrophy (ATD). The long bones measured were less than third percentile; the thoracic circumference (TC) measured 216 mm (< 2.5th percentile); the abdominal circumference (AC) measured 303.5 mm (50th-75th percentiles) and the rib cage perimeter (RCP) measured was 98 mm. The TC/AC was 0.70 (normal, 0.85) and the RCP/TC was 0.45 (normal, 0.68). Following birth diagnosis of Jeune syndrome was made based on radiographic analysis, which was subsequently confirmed by clinical and postmortem examination. This case highlights the utility of both TC/AC and RCP/TC in diagnosis of ATD and other skeletal dysplasias associated with a small thorax.

Reliability of prenatal sonographic lung biometry in the diagnosis of pulmonary hypoplasia

OBJECTIVE

The purpose of the present study was to assess the value of biometric lung measurements for the diagnosis of severe fetal pulmonary hypoplasia by investigating whether a significant correlation between two-dimensional lung biometry measurements and autopsy findings could be established.

METHODS

This was a prospective study carried out between 1995 and 1997. Nomograms for normal fetuses of the anterior-posterior and transverse inner thoracic diameters, which describe the growth and shape of the lung, were used as a basis for diagnosis of pulmonary hypoplasia in fetuses at high risk of developing the condition (the fetuses had bilateral renal agenesis or multicystic kidneys; chronic PROM <25 gestational weeks or hydrothorax). Pregnancy was terminated by abortion or intrauterine death in 29/43 high-risk fetuses and autopsies were performed. Only the 29 fetuses for which there were autopsy findings were included in the study.

RESULTS

The best plane for diagnosing pulmonary hypoplasia was the four-chamber view. The diagnostic accuracy for this view as expressed by the sensitivity was 57% for the anterior-posterior diameter and 44% for the transverse diameter; as expressed by the specificity it was 42% for the anterior-posterior diameter and 50% for the transverse diameter. The results for the four-chamber view for the various high-risk conditions were as follows: for fetuses with chronic PROM we obtained sensitivities of 75% and 50% (anterior-posterior and transverse dimensions, respectively) and specificities of 80% and 60% (anterior-posterior and transverse dimensions, respectively). The sensitivities of lung biometry in fetuses with hydrothorax were 1% and 80% for the two diameters, but there was a low specificity. In fetuses with bilateral renal agenesis or multicystic kidneys we obtained sensitivities of 36% and 30% (anterior-posterior and transverse dimensions, respectively) and a specificity of 50% (anterior-posterior dimension).

CONCLUSIONS

The present results show that two-dimensional lung biometry is not a suitable method for antenatal detection of pulmonary hypoplasia. However, in individual cases with high risk for pulmonary hypoplasia, lung biometry might prove to be an additional diagnostic parameter.

Skeletal anomalies

It is possible to identify many types of skeletal dysplasias and conditions involving limb deformities prenatally using ultrasound. It is likely that in the future, with the advancing technology and discoveries in molecular genetics, specific mutation analysis will become available for many of these conditions. This will make first trimester diagnosis an option in many cases. Because of the complex nature of many of these cases, it may be helpful to use a multidisciplinary approach involving a radiologist and a geneticist at times. In utero radiographs may help clarify a diagnosis. In lethal cases where a specific diagnosis has not been confirmed, it may be helpful postpartum to obtain an autopsy; photographs; complete body radiographs; karyotypic analysis; and specimens of bone, cartilage, and fetal blood for further analysis.

The fetal lung. 2: Pulmonary hypoplasia

This review describes the pathogenesis of pulmonary hypoplasia and highlights its clinical, radiological and pathologic features, with emphasis on oligohydramnios-related pulmonary hypoplasia. Since pulmonary hypoplasia may lead to severe respiratory distress immediately after birth and even to neonatal death, an accurate and patient-friendly prenatal test for early detection and distinction between lethal and non-lethal pulmonary hypoplasia is still highly desirable. An extended overview of the proposed methods for the prenatal prediction of pulmonary hypoplasia is presented.

Sonographic and molecular diagnosis of thanatophoric dysplasia type I at 18 weeks of gestation

Thanatophoric dysplasia is the most common type of lethal skeletal dysplasia. It can usually be diagnosed with ultrasound, but differential diagnosis with other osteochondrodysplasias is not always possible. Mutations in the fibroblast growth factor receptor 3 (FGFR3) gene have been demonstrated to cause two distinct subtypes of the disorder. We describe a case of thanatophoric dysplasia type I diagnosed at 18 weeks of gestation by ultrasonography. Genomic DNA obtained by chorionic villus sampling showed a C to G substitution at position 746 in the FGFR3 gene, resulting in a Ser249Cys substitution already known to be associated with type I disease. Implications for perinatal management are discussed.

Serial fetal lung volume measurement using three-dimensional ultrasound

OBJECTIVE

To establish reference intervals for fetal lung growth.

DESIGN

Longitudinal observational study.

SUBJECTS

Fifty-eight women with initially uncomplicated singleton pregnancies were recruited from the antenatal population of a teaching hospital. Four women were excluded from the final analysis because of complications arising in their pregnancy.

METHODS

Each subject was serially scanned at monthly intervals. At each visit lung volume was measured using an ultrasound-based computerized three-dimensional imaging system. Multilevel models were used to determine conditional and unconditional reference intervals.

RESULTS

Reference intervals for fetal lung growth were derived. Fetal lung volume increases in a non-linear way with gestation.

CONCLUSIONS

Our computerized system has the capacity to be used in conjunction with any standard two-dimensional ultrasound scanner in order to measure volume. Lung volume measurement may be useful in predicting pulmonary hypoplasia.

Ultrasonographic examination of intrauterine growth for multiple fetal dimensions in a Chinese population. Central-South China Fetal Growth Study Group

OBJECTIVE

We sought to construct an ultrasonography-based growth curve in a Chinese population.

STUDY DESIGN

Routine ultrasonographic examination was performed in 5496 normal pregnancies (>95% first births) in five obstetric ultrasonography laboratories in Central-South China from January 1, 1992, to December 31, 1993.

RESULTS

All the fetal growth measures increased with gestational age, whereas the ratios either decreased or remained constant across gestation. Biparietal diameter and cerebral hemispheric width were higher at early gestational ages, whereas femur length, thoracic circumference, and abdominal circumference were lower at later gestational ages in our study than in previous studies. The ratio of lateral ventricular width/cerebral hemispheric width was lower at an early gestational age but higher in later gestational ages in our study.

CONCLUSIONS

A different standard of ultrasonography-based fetal growth is needed for different populations. The ultrasonography-based growth curve constructed in this large Chinese population provides an additional tool for the evaluation of fetal growth and development.

The fetal thorax: noncardiac chest anomalies

Fetal thoracic anomalies often lead to pulmonary hypoplasia with subsequent fetal or neonatal demise. Therefore, in utero sonographic identification of these anomalies is important. Unlike cardiac anomalies, most noncardiac thoracic abnormalities are easily detected with ultrasound. An unusually small thorax is usually obvious to the experienced sonographer, and thoracic masses are commonly observed on the routinely obtained four-chamber view of the heart. This article reviews the many causes of pulmonary hypoplasia with an emphasis placed on thoracic masses. Many examples of pathological fetal thoracic conditions are provided as well as a listing of differential considerations with regard to sonographic appearances of chest masses.

Can Prenatal Ultrasound Predict Pulmonary Hypoplasia?

Pulmonary hypoplasia is often associated with sonographically detectable conditions: oligohydramnios, prolonged premature rupture of membranes, and, not infrequently, fetal anomalies. In their efforts to improve prenatal sonographic diagnosis of this condition, investigators have used an array of different sonographic biometric measurements and fetal behavioral patterns. Definitions of these measurements and their respective successes in predicting pulmonary hypoplasia are presented. The sonographic parameters that have been of most value in the prediction of pulmonary hypoplasia are chest circumference, direct measurements of the lung, lung length, lung span to hemithorax diameter, and more complex formulas, such as lung area/heart area x 100/chest area. Although fetal measurements may help predict pulmonary hypoplasia, no single sonographic finding consistently leads to a prediction of the presence of pulmonary hypoplasia. Therefore, obstetric management (i.e., nonintervention) cannot currently be altered with the finding of abnormal biometric parameters unless a known lethal anomaly is observed.

Prenatal ultrasonographic diagnosis of acardiac twin

Acardiac twinning is a rare complication of monozygotic twin gestation occurring in 1/35,000 pregnancies or in 1% of all monozygotic twins. This condition is characterized by partial or complete lack of development of the heart in one of the twins, and requires that the normal twin (pump twin) provides circulation for itself as well as the acardiac sibling (perfused twin) by means of reverse circulation through large artery-to-artery and vein-to-vein anastomoses. The acardiac anomaly is uniformly fatal for the perfused twin, and the perinatal mortality for the normal twin is about 50%, usually as the result of congestive heart failure, polyhydramnios, and preterm delivery. In this report we present two cases of acardiac twin prenatally diagnosed by ultrasound. The principal sonographic features for prenatal diagnosis and the clinical management are briefly discussed.

Prenatal diagnosis of short rib (polydactyly) syndrome with situs inversus

We present a case of short rib (polydactyly) syndrome in which the diagnosis was made prenatally by ultrasound examination. The more specific diagnosis of short rib (polydactyly) syndrome type III was made on the basis of findings on radiographs obtained at birth. The sonographic and radiographic features are discussed. The patient had complete situs inversus and hypospadias. The former was reported in one other case of type III and the later has not been previously reported in this entity.

Use of the fetal chest in estimating fetal weight

OBJECTIVE

This study was designed to develop formulas using the chest circumference instead of the abdominal circumference for estimating fetal weight.

STUDY DESIGN

Ultrasonographic measurements of the chest circumference, biparietal diameter, abdominal circumference, humeral length, and femoral length were obtained in 75 term fetuses of uncomplicated pregnancies within 24 hours of delivery. Three equations for fetal weight estimation that used the chest circumference, instead of the abdominal circumference, in combination with the biparietal diameter or the humeral length were developed by regression analysis.

RESULTS

The average mean errors of fetal weight estimation for these equations vary from 7.1% to 7.6%.

CONCLUSIONS

These equations may be used in predicting the birth weight when the fetal abdomen is altered by certain fetal abnormalities.

Serial thoracic versus abdominal circumference ratios for the prediction of pulmonary hypoplasia in premature rupture of the membranes remote from term

OBJECTIVES

The purpose of this study was to evaluate the fetal thoracic versus abdominal circumference ratio in the prediction of pulmonary hypoplasia after preterm premature rupture of the membranes.

STUDY DESIGN

A standard curve of thoracic versus abdominal circumference ratio versus gestational age was derived from 120 uncomplicated pregnancies. Thoracic versus abdominal circumference ratio and amniotic fluid estimations were obtained serially in 16 women with premature rupture of the membranes at less than 26 weeks' gestation.

RESULTS

An abnormal thoracic versus abdominal circumference ratio predicted lethal pulmonary hypoplasia in six infants. A progressive decline in thoracic versus abdominal circumference ratio was identified in all of these patients. Six of eight women with persistent oligohydramnios had abnormal thoracic versus abdominal circumference ratios and lethal pulmonary hypoplasia. Two surviving infants had restriction deformities and pulmonary complications.

CONCLUSIONS

In the setting of premature rupture of the fetal membranes at less than 26 weeks, serial thoracic versus abdominal circumference ratio measurement is a reliable predictor of pulmonary hypoplasia. Persistent oligohydramnios is ominous because of the risk of restriction deformities and pulmonary complications in the survivors.

The ultrasonographic assessment of the fetal thorax and fetal breathing movements in the prediction of pulmonary hypoplasia

Comparison was made of fetal breathing movements (FBM) and thoracic measurements in the prenatal diagnosis of pulmonary hypoplasia. In 20 pregnancies with oligohydramnios due to premature and prolonged rupture of the membranes (PROM) the presence or absence of FBM was assessed, the internal thoracic and cardiac circumferences were measured and the internal thoracic and lung areas calculated. All 5 infants with absent FBM died from pulmonary hypoplasia in the neonatal period and all 15 with FBM present survived. The internal thoracic circumference of 3 of the fetuses that developed pulmonary hypoplasia and 1 of those that did not were below the 2.5th centile of a reference range constructed from 76 normal pregnancies. Similarly, the lung areas were below the 2.5th centile of our reference range in 3 fetuses who developed pulmonary hypoplasia and 2 of those that survived. The absence of FBM was found to be the most accurate predictor of pulmonary hypoplasia in pregnancies complicated by oligohydramnios due to PROM.