Nuchal edema and venous-lymphatic phenotype disturbance in human fetuses and mouse embryos with aneuploidy

Piezo1 regulates meningeal lymphatic vessel drainage and alleviates excessive CSF accumulation

Piezo1 regulates multiple aspects of the vascular system by converting mechanical signals generated by fluid flow into biological processes. Here, we find that Piezo1 is necessary for the proper development and function of meningeal lymphatic vessels and that activating Piezo1 through transgenic overexpression or treatment with the chemical agonist Yoda1 is sufficient to increase cerebrospinal fluid (CSF) outflow by improving lymphatic absorption and transport. The abnormal accumulation of CSF, which often leads to hydrocephalus and ventriculomegaly, currently lacks effective treatments. We discovered that meningeal lymphatics in mouse models of Down syndrome were incompletely developed and abnormally formed. Selective overexpression of Piezo1 in lymphatics or systemic administration of Yoda1 in mice with hydrocephalus or Down syndrome resulted in a notable decrease in pathological CSF accumulation, ventricular enlargement and other associated disease symptoms. Together, our study highlights the importance of Piezo1-mediated lymphatic mechanotransduction in maintaining brain fluid drainage and identifies Piezo1 as a promising therapeutic target for treating excessive CSF accumulation and ventricular enlargement.

Nuchal Translucency and Congenital Heart Defects

Nuchal translucency comprises a temporary accumulation of fluid in the subcutaneous tissue on the back of a fetus's neck, which accompanies the crown-rump length and is observed through an ultrasound performed between 11 and 13 weeks + 6 days gestation. Nuchal translucency is considered to be above normal when values are higher than the 95th/99th percentile or equal to or higher than 2.5/3.5 mm. The first connection between increased nuchal translucency and the presence of congenital heart defects is described in the study of Hyett et al., who observed that they are directly proportional. Since that time, several studies have been conducted to understand if nuchal translucency measurements can be used for congenital heart defect screening in euploid fetuses. However, there is great variability in the estimated nuchal translucency cutoff values for congenital heart defect detection. The purpose of this review was to understand how increased nuchal translucency values and congenital heart defects are related and to identify which of these defects are more frequently associated with an increase in these values.

Angiogenic factors measured in aspirated placental tissue between the 10 + 6 and 18 + 3 weeks of gestation

This study was designed to determine the level of vascular endothelial growth factor-A (VEGF-A), basic fibroblast growth factor (bFGF) and endothelial nitric oxide synthase (eNOS) in chorionic villi during in first and second trimester, and their association with nuchal translucency (NT) measured by ultrasound. Seventy-five singleton healthy pregnancies with no detected congenital malformation were collected for NT measurements and chorionic villus sampling (CVS). Concentrations of angiogenic factors were assayed in chorionic villi sampled between 10 + 6 and 18 + 3 weeks of gestation. ENOS level was steady during this gestational period, while the concentrations of VEGF-A and bFGF significantly decreased. Placental concentrations of VEGF-A and bFGF correlated positively with each other (semi-partial correlation in multivariable linear regression (r): 0.90) and both correlated negatively with the eNOS level (r: -0.64 and r: -0.83, respectively). NT was positively correlated with eNOS concentration and negatively correlated with bFGF levels (r: 0.85 and r: -0.78, respectively). Inverse correlation was found between gestational age and VEGF-A and bFGF concentrations (r: -0.57 and r: 0.73, respectively). Alterations of angiogenic factors in chorionic villi might be an adjunct modality to NT and foetal growth as sonographic markers.

Absence of an anatomical origin for altered ductus venosus flow velocity waveforms in first-trimester human fetuses with increased nuchal translucency

OBJECTIVE

To perform a morphological evaluation of the ductus venosus, heart and jugular lymphatic sac (JLS) in first-trimester human fetuses with normal and abnormal ductus venosus flow velocity waveforms (DV-FVWs) and normal and increased nuchal translucency (NT).

METHOD

Postmortem examination was performed on fetuses with increased NT or structural malformations with previous NT and DV-FVW measurements. Ductus venosus morphology was examined using markers for endothelium, smooth muscle actin (SMA), nerves and elastic fibers. Fetal hearts were studied by microscopy. The nuchal region was analyzed using markers for lymphatic vessels, endothelium, SMA and nerves.

RESULTS

Two trisomy 21 and two trisomy 18 fetuses with increased NT and abnormal DV-FVWs were analyzed. As a control, one euploid anencephalic fetus with normal NT, cardiac anatomy and DV-FVWs was examined. Similar endothelial and SMA expression was observed in the ductus venosus in all fetuses. Nerve and elastic fiber expression were not detected. Three trisomic fetuses showed cardiac defects, one trisomic fetus demonstrated normal cardiac anatomy. The JLS was abnormally enlarged or contained red blood cells in all trisomic fetuses. The control fetus showed a normal JLS.

CONCLUSION

Abnormal DV-FVWs are not justified by alterations in ductus venosus morphology. DV-FVWs most probably reflect intracardiac pressure. © 2016 John Wiley & Sons, Ltd.

Trends in Serial Measurements of Ultrasound Markers in Second and Third Trimester Down Syndrome Fetuses

OBJECTIVES

To evaluate trends of nasal bone length (NBL), prenasal thickness (PT), nuchal fold (NF), prenasal thickness to nasal bone length (PT-NBL) ratio, and prefrontal space ratio (PFSR), measured serially in second- and third-trimester Down syndrome (DS) fetuses.

METHODS

Prenatal databases were searched for cases of continuing DS pregnancies with serial measurements, taken at least two weeks apart. Trends were plotted on previously reported normal ranges.

RESULTS

Serial measurements were available in 25 Down syndrome fetuses. Median gestational age (GA) was 25 weeks; average number of visits per case was 2.44, with a median interval of 39 days between investigations. In DS fetuses, NBL and PT showed fairly stable trends with gestation. PFSR, but especially NF, had a more unpredictable trend. The PT-NBL ratio was the most stable marker, remaining unchanged in 95% of cases. NBL, PT, and NF showed more deviance from the normal range with advancing gestation, but MoM values remained stable. All but two fetuses had ultrasound markers or structural anomalies, especially heart defects.

CONCLUSIONS

The PT-NBL ratio is the most constant DS marker throughout gestation, following a predictable trend.

Involvement of neurons and retinoic acid in lymphatic development: new insights in increased nuchal translucency

OBJECTIVE

Increased nuchal translucency originates from disturbed lymphatic development. Abnormal neural crest cell (NCC) migration may be involved in lymphatic development. Because both neuronal and lymphatic development share retinoic acid (RA) as a common factor, this study investigated the involvement of NCCs and RA in specific steps in lymphatic endothelial cell (LEC) differentiation and nuchal edema, which is the morphological equivalent of increased nuchal translucency.

METHODS

Mouse embryos in which all NCCs were fluorescently labeled (Wnt1-Cre;Rosa26(eYfp) ), reporter embryos for in vivo RA activity (DR5-luciferase) and embryos with absent (Raldh2(-/-) ) or in utero inhibition of RA signaling (BMS493) were investigated. Immunofluorescence using markers for blood vessels, lymphatic endothelium and neurons was applied. Flow cytometry was performed to measure specific LEC populations.

RESULTS

Cranial nerves were consistently close to the jugular lymph sac (JLS), in which NCCs were identified. In the absence of RA synthesis, enlarged JLS and nuchal edema were observed. Inhibiting RA signaling in utero resulted in a significantly higher amount of precursor-LECs at the expense of mature LECs and caused nuchal edema.

CONCLUSIONS

Neural crest cells are involved in lymphatic development. RA is required for differentiation into mature LECs. Blocking RA signaling in mouse embryos results in abnormal lymphatic development and nuchal edema.

Development of secondary lymphoid organs in relation to lymphatic vasculature

Although the initial event in lymphatic endothelial specification occurs slightly before the initiation of lymph node formation in mice, the development of lymphatic vessels and lymph nodes occurs within the same embryonic time frame. Specification of lymphatic endothelial cells starts around embryonic day 10 (E10), followed by endothelial cell budding and formation of the first lymphatic structures. Through lymphatic endothelial cell sprouting these lymph sacs give rise to the lymphatic vasculature which is complete by E15.5 in mice. It is within this time frame that lymph node formation is initiated and the first structure is secured in place. As lymphatic vessels are crucially involved in the functionality of the lymph nodes, the recent insight that both structures depend on common developmental signals for their initiation provides a molecular mechanism for their coordinated formation. Here, we will describe the common developmental signals needed to properly start the formation of lymphatic vessels and lymph nodes and their interdependence in adult life.

Embryology of the heart and its impact on understanding fetal and neonatal heart disease

Heart development is a complex process during which the heart needs to transform from a single tube towards a fully septated heart with four chambers and a separated outflow tract. Several major events contribute to this process, that largely overlap in time. Abnormal heart development results in congenital heart disease, which has an estimated incidence of 1% of liveborn children. Eighty percent of cases of congenital heart disease are considered to have a multifactoral developmental background, whereas knowledge of monogenetic causes for congenital heart disease is still limited. This review focuses on several novel findings in cardiac development that might enhance our knowledge of aetiology and support refinement of prenatal diagnosis of congenital heart disease.

The anatomy of fetal peripheral lymphatic vessels in the head-and-neck region: an immunohistochemical study

Using D2-40 immunohistochemistry, we assessed the distribution of peripheral lymphatic vessels (LVs) in the head-and-neck region of four midterm fetuses without nuchal edema, two of 10 weeks and two of 15 weeks' gestation. We observed abundant LVs in the subcutaneous layer, especially in and along the facial muscles. In the occipital region, only a few LVs were identified perforating the back muscles. The parotid and thyroid glands were surrounded by LVs, but the sublingual and submandibular glands were not. The numbers of submucosal LVs increased from 10 to 15 weeks' gestation in all of the nasal, oral, pharyngeal, and laryngeal cavities, but not in the palate. The laryngeal submucosa had an extremely high density of LVs. In contrast, we found few LVs along bone and cartilage except for those of the mandible as well as along the pharyngotympanic tube, middle ear, tooth germ, and the cranial nerves and ganglia. Some of these results suggested that cerebrospinal fluid outflow to the head LVs commences after 15 weeks' gestation. The subcutaneous LVs of the head appear to grow from the neck side, whereas initial submucosal LVs likely develop in situ because no communication was evident with other sites during early developmental stages. In addition, CD68-positive macrophages did not accompany the developing LVs.

Role of the vascular endothelial growth factor in the inverse relationship between increased nuchal translucency thickness and fetomaternal transfusion

OBJECTIVE

To elucidate the possible etiological role of the vascular endothelial growth factor (VEGF) in the inverse correlation between nuchal translucency (NT) thickness and fetomaternal transfusion (FMT).

METHODS

The level of FMT was determined prospectively in 80 viable, singleton pregnancies in which 10-14-week ultrasonographic scanning, NT thickness measurement; chorionic villus sampling (CVS) for fetal karyotyping and VEGF concentration determination were performed. The grouping procedures were based either on NT thickness (<2 MoM in Group I, and ≥2 MoM in Group II), or on karyotype (euploid in Group A, and aneuploid in Group B). The level of FMT was determined via maternal serum α-fetoprotein levels before and after CVS. The FMT and the VEGF concentration of the chorionic tissue were analysed in comparisons between Groups I and II, and between Groups "A" and "B".

RESULTS

The mean level of FMT after CVS was 72.5±21.3 μL and 19.28±5.4 μL in Groups I (n=44) and II (n=36), respectively (P<0.02). The VEGF concentration of the chorionic tissue in Groups I and II was 40.6±16.7 pg/mg protein and 21.1±6.3 pg/mg protein, respectively (P=0.28). The mean level of FMT was 57.9±15.0 μL and 8.1±3.9 μL in Groups A and B, respectively (P<0.003). The VEGF concentration of the chorionic tissue in Groups A and B was 25.9±10.7 pg/mg protein and 21.3±11.3 pg/mg protein, respectively (P=0.77).

CONCLUSION

No difference exists in the VEGF concentration in the aspirated chorionic tissue between Groups I and II and between Groups A and B. A higher level of FMT was observed among the aneuploid pregnancies after CVS than among the euploid cases. Chorionic VEGF does not influence the inverse relationship between the pre-CVS NT thickness and FMT.

Aberrant lymphatic development in euploid fetuses with increased nuchal translucency including Noonan syndrome

OBJECTIVE

Increased nuchal translucency in the human fetus is associated with aneuploidy, structural malformations and several syndromes such as Noonan syndrome. In 60–70% of the Noonan syndrome cases, a gene mutation can be demonstrated. Previous research showed that aneuploid fetuses with increased nuchal translucency (NT) demonstrate an aberrant lymphatic endothelial differentiation.

METHOD

Fetuses with increased NT and normal karyotype (n = 7) were compared with euploid controls having normal NT (n = 5). A Noonan syndrome gene mutation was found in three out of seven fetuses with increased NT. Endothelial differentiation was evaluated by immunohistochemistry using lymphatic markers (PROX-1, Podoplanin, LYVE-1) and blood vessel markers vascular endothelial growth factor-A (VEGF-A), Neuropilin-1 (NP-1), Sonic hedgehog, von Willebrand factor, and the smooth muscle cell marker, smooth muscle actin.

RESULTS

Nuchal edema and enlarged jugular lymphatic sacs (JLSs) were observed in fetuses with increased NT, together with abnormal lymphatic endothelial differentiation i.e. the presence of blood vessel characteristics, including high levels of VEGF-A and NP-1 expression. The enlarged JLSs contained erythrocytes and were surrounded by smooth muscle cells.

CONCLUSION

This study shows an aberrant lymphatic endothelial differentiation in fetuses with increased NT and a normal karyotype (including Noonan syndrome fetuses), as was previously reported before in aneuploid fetuses.

New insights into the development of lymphoid tissues

Secondary lymphoid organs are important locations for the initiation of adaptive immune responses. They develop before birth, and their formation requires interaction between lymphotoxin-α₁ß₂-expressing lymphoid-tissue inducer cells and lymphotoxin-ß receptor-expressing stromal organizer cells. Here, we discuss new insights into the earliest phases of peripheral lymph node and Peyer's patch formation that occur before lymphotoxin-ß receptor signalling and suggest a role for the developing nervous system. In addition, we discuss the differing requirements for the postnatal formation of mucosa-associated lymphoid tissues and tertiary lymphoid structures that develop at sites of chronic inflammation.

Abnormal ductus venosus flow in first-trimester fetuses with increased nuchal translucency: relationship with the type of cardiac defect?

OBJECTIVE

The purpose of this study was to evaluate ductus venosus flow velocities and a possible relationship with the type of cardiac defect in fetuses with increased nuchal translucency (NT).

METHODS

Seventy-two fetuses with normal NT and 137 fetuses with increased NT (>95th percentile) were evaluated. The ductus venosus pulsatility index for veins (PIV), late diastolic velocity (velocity during atrial contraction [a-V]), and intracardiac velocities were evaluated. In cases of pregnancy termination, a postmortem examination was performed. Cardiac defects were grouped into septal defects, left and right inflow obstruction, left and right outflow obstruction, and other defects. Data were evaluated by multilevel analysis.

RESULTS

A cardiac defect was found in 45 fetuses with increased NT. Fetuses with increased NT showed a higher ductus venosus PIV and a lower a-V compared to fetuses with normal NT (P < .05). Within the group of fetuses with increased NT, a higher PIV and a lower a-V were found in cases with a cardiac defect compared to cases with a normal heart (P < .001). No differences in PIV and a-V were found between the types of cardiac defects. Intracardiac velocities showed no differences between fetuses with normal and increased NT, irrespective of the presence of a cardiac defect.

CONCLUSIONS

Ductus venosus flow velocities in fetuses with increased NT are not related to a certain type of cardiac defect. This indicates that the altered ductus venosus flow velocities found in fetuses with increased NT cannot be explained by cardiac failure due to a specific altered cardiac anatomy.

Altered jugular vein and ductus venosus flow velocities in fetuses with increased nuchal translucency and distended jugular lymphatic sacs

OBJECTIVE

We sought to assess blood flow in relation to jugular lymphatic distension in fetuses with increased and normal nuchal translucency (NT).

STUDY DESIGN

In all, 72 fetuses with normal NT and 71 fetuses with NT >95th percentile were evaluated. NT size, jugular lymphatic sacs (JLS), jugular vein and ductus venosus pulsatility index for veins (PIV), and intracardiac velocities were measured.

RESULTS

JLS were visualized in 22/72 fetuses with normal and in 55/71 fetuses with increased NT. Jugular vein and ductus venosus PIV was higher in fetuses with increased NT compared to normal NT (P < .01). Visibility of JLS was associated with a higher ductus venous PIV (P < .05), but not with a higher jugular vein PIV. Larger NT and larger JLS volumes were associated with higher jugular vein and ductus venosus PIV (P < .05).

CONCLUSION

This study shows a relation among increased NT, jugular lymphatic distension, and altered blood flow in jugular vein and ductus venosus.

Lymphatic capillary hypoplasia in the skin of fetuses with increased nuchal translucency and Turner's syndrome: comparison with trisomies and controls

Fetuses with Turner's syndrome or trisomies 21, 18 and 13 show excess of skin, which can be visualized by ultrasonography as increased nuchal translucency at 11-13(+6) weeks' gestation. The objective of this study was to gain insight in the development and distribution of blood vessels, lymphatic capillaries of the cutis and lymphatic collectors of the cutis and subcutis and to study developmental changes with increasing gestation. Immunofluorescence of cryosections with 10 specific antibodies was used to investigate the nuchal skin of three fetuses with Turner syndrome's and to differentiate lymphatics, lymph capillaries (FLT4, PTN 63, LYVE1, PROX1), blood vessels (KDR, CD 31, PDPN), blood clotting activity (von Willebrand factor), basement membranes and big vessels (Laminin, Collagen Type IV). The findings were compared with those in seven fetuses with trisomy 21 and two fetuses each with trisomies 18 or 13, respectively, as well as six normal controls. Immunoreactive receptors for vascular endothelial growth factors (FLT4) were decreased in lymphatic capillaries of the skin of Turner fetuses. Accordingly, LYVE1 was scarce and PROX1 staining was less intense in the dermis of Turner fetuses. Lymphatic collectors were, however, evenly stained. In normal fetuses and in those with trisomies, lymphatic capillaries were evenly distributed. We conclude that lymphatic capillary hypoplasia might be responsible for nuchal cystic hygroma in Turner syndrome. The biological basis for increased nuchal translucency in trisomies may however be different.

Nuchal translucency and lymphatic system maldevelopment

We describe the histological examination of 18 aborted fetuses that had increased nuchal translucency (NT) between 11(+0) and 13(+6) weeks' gestation. The aim of this study was to assess the corresponding NT anatomic features by immunohistochemical (IHC) investigation. A morphological study was performed using lymphatic and blood endothelial specific markers, as well as smooth muscle actin (SMA). We found that all 18 cases were D2-40 positive, CD31 positive, and CD34 negative, suggesting the presence of nuchal lymph vessel ectasia. We found that 12/18 cases were SMA staining positive and 6/18 cases were SMA negative, suggesting that 6/18 cases had nuchal cystic lymphangiectasia, whereas 12/18 had cystic hygromas. The present data seem to confirm the reasonable hypothesis that lymphangiogenesis plays a relevant role in nuchal edema, increased NT, and that increased NT is the result of a lymphatic malformation or a delayed development of the lymphatic system.

Abnormal Shh and FOXC2 expression correlates with aberrant lymphatic development in human fetuses with increased nuchal translucency

OBJECTIVE

Previous research in fetuses with increased nuchal translucency (NT) showed abnormal lymphatic endothelial differentiation characteristics, including increased vascular endothelial growth factor (VEGF)-A expression, and aberrant smooth muscle cells (SMCs) surrounding enlarged jugular lymphatic sacs (JLS). We hypothesized that abnormal Sonic hedgehog (Shh) expression would result in altered VEGF-A signaling in the lymphatic endothelial cells of the JLS and that aberrant acquisition of SMCs could be caused by downregulation of forkhead transcription factor FOXC2 and upregulation of platelet-derived growth factor (PDGF)-B in the lymphatic endothelial cells of the JLS.

METHODS

Five trisomy 21 fetuses and four controls were investigated using immunohistochemistry for Shh, VEGF-A, FOXC2 and PDGF-B expression in the lymphatic endothelial cells of the JLS.

RESULTS

An increased Shh, VEGF-A and PDGF-B expression, and decreased FOXC2 expression were shown in the lymphatic endothelial cells of the JLS of the trisomic fetuses.

CONCLUSIONS

Increased Shh and VEGF-A expression is correlated with an aberrant lymphatic endothelial differentiation in trisomy 21 fetuses. The SMCs surrounding the JLS can possibly be explained by an increase of PDGF-B-induced SMC recruitment and/or differentiation. This underscores earlier findings that indicate the loss of lymphatic identity in trisomy 21 fetuses and a shift towards a blood vessel wall phenotype.

Jugular lymphatic sacs in first-trimester fetuses with normal nuchal translucency

OBJECTIVE

To assess the ultrasonographic appearance of the jugular lymphatic sacs (JLS) in first-trimester fetuses with a normal nuchal translucency (NT).

METHODS

Seventy-five fetuses with a normal NT thickness (< 95(th) percentile) were examined weekly between 11 and 17 weeks of gestation. After measurement of the NT thickness, the neck region was examined using both transvaginal and transabdominal ultrasonography for the presence of JLS. If present, their dimensions were measured in three directions and the volume was calculated using the formula for a spheroid. Data were analyzed using multilevel analysis.

RESULTS

Seventy-five fetuses were evaluated and a total of 243 ultrasound examinations of the neck region were performed. In 25 (33%) of the 75 fetuses, the JLS could be observed once or more than once. In 19 fetuses JLS were visualized once, in five fetuses twice and in one fetus three times. In total, the JLS were visualized 32 times (n = 15 bilaterally, n = 15 only the left JLS and n = 2 only the right JLS). Relatively greater NT thickness was associated with a higher probability of the presence of JLS, although this was not statistically significant (NT < 1 mm, probability 0.07; NT 1-2 mm, probability 0.15, P = 0.10; NT > 2 mm, probability 0.20, P = 0.08). Gestational age was predictive for the presence of JLS, with the highest probability between 13 and 15 weeks of gestation (P < 0.01). No relationship was found between gestational age and the volumes of the left and right JLS.

CONCLUSION

The JLS can be visualized on ultrasound examination in a significant proportion of fetuses with normal NT, most often between 13 and 15 weeks of gestation, and this does not seem to be associated with any abnormality in these fetuses.

Jugular lymphatic sacs in the first trimester of pregnancy: the prevalence and the potential value in screening for chromosomal abnormalities

OBJECTIVE

To investigate the prevalence of detectable jugular lymphatic sacs in a setting for first trimester screening for Down syndrome, and to evaluate the influence of jugular lymphatic sacs on the screening performance for chromosomal abnormalities.

METHODS

A prospective single center study (Erasmus University Medical Center, Rotterdam, The Netherlands) over a period of one year (January 2003-February 2004). First trimester nuchal translucency measurement was performed in a study population of 415 fetuses. Additionally, the transversal plane with the spine and mandible was visualized to verify the presence of jugular lymphatic sacs. The jugular lymphatic sacs were measured anterior-posterior. The association between nuchal translucency and jugular lymphatic sacs was tested.

RESULTS

Follow-up was complete in 406 cases (97.8%). Jugular lymphatic sacs could be visualized in 98 out of 415 (23.5%). The nuchal translucency thickness and the mean of the left and right jugular lymphatic sac were significantly correlated.

CONCLUSION

The sonographic visualization of jugular lymphatic sacs significantly predicts chromosomal abnormalities, although nuchal translucency is a better predictor. Nuchal translucency and jugular lymphatic sacs are strongly correlated and therefore not applicable in a combination test.

Jugular lymphatic maldevelopment in Turner syndrome and trisomy 21: different anomalies leading to nuchal edema

Increased nuchal translucency (NT), morphologically known as nuchal edema, is an ultrasound marker for aneuploidy. Turner syndrome presents with massive NT, called cystic hygroma. Conflicting data exist as to whether cystic hygroma and increased NT are different entities. Both are associated with jugular lymphatic distension. The authors investigated jugular lymphatics of trisomy 21, Turner syndrome, and normal karyotype fetuses. Fetuses were investigated using immunohistochemistry for blood vascular, lymphatic, and smooth muscle cell markers. Trisomy 21 fetuses showed nuchal cavities within the mesenchymal edema negative for endothelial markers. These were extremely large in Turner fetuses, showing similar characteristics. The skin showed numerous dilated lymphatics in the case of trisomy 21 and scanty small lymphatics in Turner fetuses. A jugular lymphatic sac was present in control and trisomy 21 fetuses and was enlarged in trisomy 21 cases. In Turner fetuses, no jugular lymphatic sac was observed. Nuchal edema in trisomy 21 and Turner syndrome appears to be a similar entity caused by different lymphatic abnormalities.

Nuchal Translucency and First Trimester Risk Assessment

First-trimester risk assessment for fetal aneuploidy using nuchal translucency (NT) measurement is rapidly gaining popularity in the United States. In combination with maternal serum markers in the first trimester, the screening performance is exceptionally good, with detection rates of more than 80% at a screen positive rate of 5%. Recently, the method has been validated for screening for Down syndrome and other aneuploidies in multicenter trials in the United States and elsewhere. Compliance with established criteria for measurement of the NT is essential to achieve uniform reliability and high screening test sensitivity. There is an international consensus about the importance of specific training in the NT examination, conformity to standards of NT measurement, and regular audit for quality assurance. In the United States, the Nuchal Translucency Quality Review program has been developed to administer credentialing and quality review for registered practitioners. The Nuchal Translucency Quality Review credentials signify the proficiency of the sonographer or sonologist in NT measurement and participation in a regular quality assurance audit. We encourage accreditation of clinical sites offering first-trimester risk assessment to ensure the highest quality care.

Temporal Relationship Between Increased Nuchal Translucency and Enlarged Jugular Lymphatic Sac

OBJECTIVE

To study the relationship between the volume of the jugular lymphatic sacs and nuchal translucency thickness in fetuses with increased nuchal translucency with advancing gestation.

METHODS

Seventy-four fetuses with a nuchal translucency greater than the 95th percentile were examined weekly between 11 and 17 weeks of gestational age. The fetal neck region was studied by ultrasonography, followed by measurement of nuchal translucency and jugular lymphatic sacs. The measurements were analyzed using multilevel analysis. In case of termination of pregnancy postmortem examination was performed.

RESULTS

In 40 euploid fetuses and 34 aneuploid fetuses, 159 measurements of jugular lymphatic sac volume and nuchal translucency thickness were analyzed. The volume of the jugular lymphatic sacs and gestational age showed a quadratic relation, which differed between euploid and aneuploid fetuses (P < .01). The maximum volumes were larger and present longer in fetuses with aneuploidy than in euploid fetuses (P < .01). In case of a cardiac anomaly, jugular lymphatic sac volume was larger than in cardiac normal fetuses (nonsignificant). Furthermore, the development of jugular lymphatic sac volume and increased nuchal translucency were related, whereby an increase of the nuchal translucency preceded enlargement of the jugular lymphatic sacs (P < .001). In each fetus an increase in jugular lymphatic sac volume was followed by a decrease with advancing gestation. The gestational age at maximum jugular lymphatic sac volume differed between fetuses, indicating a fetus-specific pattern. Nuchal translucency development showed a similar pattern. Postmortem examination confirmed distension of the jugular lymphatic sacs in all cases.

CONCLUSION

Increased nuchal translucency is associated with abnormal lymphatic development, in which nuchal translucency enlargement precedes enlargement of jugular lymphatic sacs on ultrasound examination. Aneuploid fetuses have a more disturbed lymph angiogenesis.

LEVEL OF EVIDENCE

III.