Fetal nuchal fluid--physiological or pathological?--In pregnancies less than 17 menstrual weeks

[Down syndrome screening by ultrasound]

The nuchal translucency is the usual subcutaneous space, between the skin and the soft tissues covering the fetus'neck spine, observed by ultrasound during the first trimester of pregnancy. It increases with gestational age. The association between nuchal translucency thickness and risk of Down syndrome was firstly observed in high risk populations as an old maternal age or a history of a previous child affected by Down syndrome. However, these studies are retrospective and only report the issue among pregnancies associated with an abnormal nuchal translucency thickness. Furthermore, as the performance of a screening test is correlated to the prevalence of the disease in the studied population, such results can not be extrapolated to the general population. To date, eleven prospective studies have been published, assessing the performance of the nuchal translucency measurement in a general population, including about 125,000 patients. The global sensitivity of this screening was 70% for a false positive rate of 5%. For an adjusted risk on the maternal age, the detection rate increased up to 77%. Although nuchal translucency measurement is an early and performing screening tool, uncertainties remain nevertheless about its reproducibility in the general population. In order to correctly measure the nuchal translucency, a previous training course is necessary to guarantee adequate and reproducible measurements.

Fetal lateral neck cysts: the significance of associated findings

OBJECTIVES

The detection of fetal lateral neck cysts (FLNC) may create anxiety and confusion among pregnant woman and their physicians. We attempted to determine the incidence and significance of FLNC. Also, we tried to define the importance of the associated findings: the laterality of the finding, triple test results, maternal age and other ultrasonographic findings.

METHODS AND MATERIALS

Between January 2000 and September 2003, 80 fetuses were evaluated at our institution for FLNC out of 3350 ultrasonic scans done for fetal malformations at 14-16 weeks' gestation.

RESULTS

The incidence of FLNC was 2.4% (80/3350). The majority of cases were isolated (53/80, 66%) and unilateral (46/80, 58%). Down syndrome was associated with nonisolated FLNC.

CONCLUSION

Whether the finding was unilateral or bilateral had no significance. Associated increased nuchal translucency (NT) was of importance. Furthermore, the sole finding of increased NT is significant and the finding of the FLNC has no added value. There was no correlation between isolated FLNC without NT and fetal aneuploidy. However, other risk factors increase the risk for aneuploidy by up to 15 fold.

Nuchal translucency and other first-trimester sonographic markers of chromosomal abnormalities

There is extensive evidence that effective screening for major chromosomal abnormalities can be provided in the first trimester of pregnancy. Prospective studies in a total of 200,868 pregnancies, including 871 fetuses with trisomy 21, have demonstrated that increased nuchal translucency can identify 76.8% of fetuses with trisomy 21, which represents a false-positive rate of 4.2%. When fetal nuchal translucency was combined with maternal serum free-beta-human chorionic gonadotropin and pregnancy-associated plasma protein-A in prospective studies in a total of 44,613 pregnancies, including 215 fetuses with trisomy 21, the detection rate was 87.0% for a false-positive rate of 5.0%. Studies from specialist centers with 15,822 pregnancies, which included 397 fetuses with trisomy 21, have demonstrated that the absence of the nasal bone can identify 69.0% of trisomy 21 fetuses, which represents a false-positive rate of 1.4%. It has been estimated that first-trimester screening by a combination of sonography and maternal serum testing can identify 97% of trisomy 21 fetuses, which represents a false-positive rate of 5%, or that the detection rate can be 91%, which represents a false-positive rate of 0.5%. In addition to increased nuchal translucency, important sonographic markers for chromosomal abnormalities, include fetal growth restriction, tachycardia, abnormal flow in the ductus venosus, megacystis, exomphalos and single umbilical artery. Most pregnant women prefer screening in the first, rather than in the second, trimester. As with all aspects of good clinical practice, those care givers who perform first-trimester screening should be trained appropriately, and their results should be subjected to external quality assurance.

Noonan syndrome: a cryptic condition in early gestation

Noonan syndrome is one of the most common of genetic syndromes and manifests at birth, yet it is usually diagnosed during childhood. Although prenatal diagnosis of Noonan syndrome is usually not possible, in a few cases the ultrasonographic findings suggested the diagnosis in utero. Reported sonographic clues include septated cystic hygroma, hydrothorax, polyhydramnios, and cardiac defects, such as pulmonic stenosis and hypertrophic cardiomyopathy. During a 6-year period, 46,224 live-born infants were delivered at the Chaim Sheba Medical Center. Seven newborn infants and four fetuses were found to have Noonan syndrome. One fetus showed transient nuchal translucency of 4 mm and bilateral neck cysts at the 13th gestational week. Both findings resolved spontaneously by the 18th gestational week, but during the third trimester this fetus developed hydrothorax, skin edema, and polyhydramnios. In the three other fetuses, first- and second-trimester ultrasonographic findings were normal, and the diagnosis of Noonan syndrome was suggested only during the third trimester. All three fetuses had polyhydramnios and skin edema. A cardiac malformation, hydrothorax, and a large head were present in one fetus. Sonographic facial findings were investigated. In all four fetuses posteriorly angulated, apparently low-set ears and depressed nasal bridge were identified. Wide nasal base was seen in two fetuses. In two fetuses, persistent opening of the fetal mouth was interpreted as fetal hypotonia. One fetus developed progressive postnatal hypertrophic cardiomyopathy and in one case, pulmonic stenosis became apparent at age 6 months. This small series suggests that Noonan syndrome has an evolving phenotype during in utero and postnatal life. Amelioration of early nuchal region findings and late onset of the more "typical" ultrasonographic changes may limit early prenatal detectability.

First trimester screening for aneuploidy: nuchal translucency sonography

Prenatal diagnosis of fetal aneuploidy is a continuously and rapidly evolving area of research. Currently in the United States, the standard of care for screening pregnancies for aneuploidy involves assessment of maternal age together with the use of multiple second trimester maternal serum markers. This screening approach identifies approximately 60% of pregnancies with fetuses affected with Down syndrome and provides results in the second trimester of pregnancy. First trimester screening for aneuploidy by using nuchal translucency sonography is one of the most promising areas of research in the detection of Down syndrome. This screening method involves measuring the normal space located between the cervical spine and overlying fetal skin at 10 to 14 weeks' gestation. Studies from both high risk and unselected patient populations suggest significant advantages to this approach for Down syndrome detection compared with currently available second trimester screening methods. The combination of first trimester biochemical screening and nuchal translucency measurements may further improve the efficacy of prenatal screening for aneuploidy. The article reviews studies suggesting a role for nuchal-translucency-based aneuploidy screening and describes areas of ongoing research in this field.

Outcome of chromosomally normal livebirths with increased fetal nuchal translucency at 10-14 weeks' gestation

The aim of this study was to determine the outcome of chromosomally normal livebirths with increased fetal nuchal translucency at 10-14 weeks' gestation. Clinical follow up of 89 chromosomally normal livebirths that in fetal life had a minimum nuchal translucency thickness of 3.5 mm and a comparison group of 302 infants whose fetal nuchal translucency thickness at 10-14 weeks of gestation was less than 3.5 mm was performed. Major abnormalities, mainly structural defects of the cardiovascular or skeletal systems, were found in 10.1% (nine of 89) of the group with increased translucency, compared to 2% (five of 302) in those with translucency of less than 3.5 mm (chi2=11.9, p<0.001). Delay in achievement of developmental milestones was observed in one of the infants with increased translucency and in one of the comparison group. The findings of this study show that in chromosomally normal fetuses increased nuchal translucency thickness at 10-14 weeks of gestation is a marker for fetal abnormalities including structural defects and genetic syndromes.

Increased nuchal translucency as a marker for fetal chromosomal defects

BACKGROUND

Screening for trisomy 21 (Down's syndrome) by measuring maternal serum alpha-fetoprotein, chorionic gonadotropin, and estriol concentrations and then performing chorionic-villus sampling or amniocentesis identifies approximately 60 percent of fetuses with this disorder. We used ultrasonography to detect increased nuchal translucency and cystic hygroma, which are characteristic features of fetuses with chromosomal defects.

METHODS

We performed transvaginal ultrasonography in 10,010 unselected adolescents and women less than 40 years of age with live singleton fetuses at 10 to 15.9 weeks of gestation. Increased fetal nuchal translucency was defined as an area of translucency at least 3 mm in width, and cystic hygromas were defined as septated, fluid-filled sacs in the nuchal region. Subjects whose fetuses had these findings were offered fetal karyotyping. Information on pregnancies, deliveries, and neonates was subsequently obtained from hospital records and national birth and malformation registries.

RESULTS

Nuchal translucency or cystic hygroma was seen in 76 fetuses (0.8 percent), of which 18 (24 percent) had an abnormal karyotype. The sensitivity for trisomies 21, 18, and 13 combined was 62 percent (13 of 21 fetuses), and the sensitivity for trisomy 21 alone was 54 percent (7 of 13 fetuses).

CONCLUSIONS

The use of transvaginal ultrasonography to detect increased nuchal translucency and cystic hygroma is a sensitive test for fetal aneuploidy. It can be done earlier in pregnancy than serum screening, and it decreases the subsequent need for chorionic-villus sampling or amniocentesis.

Ultrasound imaging of fetal neck anomalies: implications for the risk of aneuploidy and structural anomalies

This study summarizes 24,000 transvaginal ultrasound examinations which were performed in a predominantly low-risk population at 14-16 weeks' gestation. 1254 (5.2 per cent) fetuses had a nuchal fold or a non-septated cystic hygroma. Of these fetuses, 140 (11.1 per cent) had additional structural anomalies. Cardiovascular anomalies were the most commonly detected structural malformations. Forty-three (3.4 per cent) fetuses were aneuploid. Trisomy 21 was the most common chromosomal anomaly (n = 27). Aneuploidy was significantly more common in fetuses who had a nuchal finding and an associated structural anomaly. The prevalence of nuchal fold and non-septated cystic hygroma, as well as the incidence of their associated structural anomalies, was similar. Based on these data, it is concluded that a complete ultrasonic survey of the fetus and karyotyping are advocated in fetuses with a nuchal abnormality, irrespective of maternal age or triple serum screening results.

Abnormal nuchal findings on screening ultrasonography: aneuploidy stratification on the basis of ultrasonographic anomaly and gestational age at detection

OBJECTIVE

Our purpose was to determine the specific likelihood of different aneuploidies by gestational age in patients with nuchal folds and simple and septated nuchal membranes.

STUDY DESIGN

Retrospective database analysis was performed of 158 consecutive patients with a nuchal fold or simple or septated nuchal membrane on either abdominal or vaginal ultrasonography.

RESULTS

Thirty-eight patients with nuchal folds, 65 with simple nuchal membranes, and 55 with septated nuchal membranes were evaluated. Septated nuchal membranes were associated with the highest incidence of karyotypic abnormalities (> 50%). A peak incidence of trisomy 21 (27%) was found in the early midtrimester, leveling off to 11% by the late midtrimester. The late first trimester had a high incidence of trisomy 18 (22%), occurring more frequently than 45,X.

CONCLUSION

Ultrasonographic anomalies in the posterior neck are associated with aneuploidy from 21% to 58% of the patients in this selected population. Each anomaly has different risks for aneuploidy type, varying with gestational age at diagnosis.

Nuchal translucency cannot be used as a screening test for chromosomal abnormalities in the first trimester of pregnancy in a routine ultrasound practice

We decided to assess the practicability of introducing nuchal translucency (NT) measurements as a screening programme for fetal Down's syndrome in the first trimester of pregnancy, within the population of women who receive ultrasound examinations in our department. Over a 1-year period, measurements were made in 923 fetuses at < or = 13 weeks' gestation. Fifty-two per cent of the mothers were 36 years or older or had a past history of a chromosomally abnormal fetus or child. Measurements were only successful 58 per cent of the time; this improved to 74 per cent if the fetus was > or = 10 weeks' gestation. Inter-observer variability did not cause a major problem. There were 36 fetuses with an NT > or = 3 mm. Two of these fetuses had a chromosomal abnormality (both trisomy 21). The translucency in these two cases was so large that they would have been detected and offered prenatal diagnosis even prior to this study. There was a total of ten aneuploidies in the study group. Only two of these fetuses were detected by this screening method; five had an NT measurement < 3 mm and in three fetuses (all trisomy 21), measurements were not successful. We outline the practical problems that could be expected by introducing ultrasound screening in a routine setting. Although the efficacy of the test in a research setting may seem good, the effectiveness in everyday usage appears much less impressive, making its uptake as a screening technique in a general ultrasound practice at this stage imprudent.

Early midtrimester fetal nuchal thickness: effectiveness as a marker of Down syndrome

OBJECTIVE

Our purpose was to assess the validity of nuchal thickness in the prediction of Down syndrome in early midtrimester fetuses.

STUDY DESIGN

In 1543 consecutive pregnancies undergoing amniocentesis, primarily for advanced maternal age, nuchal thickness was prospectively measured between 13 and 18 weeks and then correlated with the karyotype obtained from amniotic fluid.

RESULTS

With the cutoff value suggested in the literature (> or = 6 mm), 33.3% (6/18) of the cases of Down syndrome would be detected for a 0.1% (2/1424) false-positive rate, with a positive predictive value adjusted to a prevalence of Down syndrome in the general population of 1:3. To increase the sensitivity of the method, the threshold was lowered to 5 mm, achieving a sensitivity of 77.8% (14/18) for a 2.1% (30/1424) false-positive rate and an adjusted positive value of 1:19.

CONCLUSIONS

In early midtrimester fetuses decreasing the nuchal thickness threshold to 5 mm substantially enhances the detection of Down syndrome with a reasonable false-positive rate.

Cystic hygroma: comparison between prenatal and postnatal diagnosis

Antenatal diagnosis of congenital malformation often leads to opportunities for intervention in the pregnancy that may have a profound effect on the outcome of the fetus. The accuracy of the diagnostic technique is a critical factor in judging the appropriateness of such interventions. This article reports the current accuracy of prenatal ultrasound diagnosis of cystic hygroma (CH) in a region with a population of 3.5 million and an annual birth rate of 52,000. During a 32-month period (to December 1994), 113 diagnoses of CH were reported to the South East Thames Regional Congenital Malformation Registry. Eighty-nine diagnoses were made prenatally and 24 were made postnatally (at delivery or postmortem). The number of confirmed cases of CH was 52 (46% total diagnoses). The prenatal diagnoses were established at a mean gestational age of 19 weeks. Fifty-six (63%) pregnancies with a prenatal diagnosis of fetal CH were terminated; in only 25% of these was the presence of CH confirmed after termination. Overall, of the 89 prenatal diagnoses, 28 (32%) were confirmed, 45 (50%) were incorrect, and 16 (18%) could not be confirmed or refuted. Only 24% of fetuses with a prenatal diagnosis of CH were live born. The survival rate at 1 year for the live-born infants with CH in this series was 88%. The diagnosis of fetal CH has a recognised association with chromosomal abnormalities, and consequently may lead to termination of the pregnancy. A potential error rate of almost 70% in the prenatal ultrasound diagnosis of this condition requires clinicians to adopt a more cautious approach to the management of the fetus with "cystic hygroma."

Antenatal diagnosis of cystic hygroma or nuchal pad--report of 92 cases with follow up of survivors

Information on the outcome of pregnancy was collected on 92 fetuses with cystic hygroma or nuchal pad, identified prenatally. Forty three (47% of the total) were associated with abnormal karyotype. Twenty five (27%) had normal karyotype but an additional abnormality was identified on ultrasound scan. There were 10 liveborn babies in this group of whom seven had significant problems postnatally. In twenty four (26%) cases the cystic hygroma or nuchal pad was an isolated finding. Seventeen (89% of those in which the pregnancy was electively continued) were liveborn and reported to be normal. Those with a normal karyotype, no other anomaly identified on antenatal scan, and smaller non-septate lesions have a good prognosis.

Fetal nuchal oedema and antenatal diagnosis of trisomy 10

Trisomy 10 was detected at amniocentesis undertaken following observation of fetal nuchal oedema. This is the first report of fetal trisomy 10 in association with nuchal oedema. The physical features of fetal trisomy 10 are described.

Nuchal translucency in the first trimester

All fetuses reported as having nuchal (nape of the neck) thickening or translucency detected by a first trimester ultrasound at 2 centres were reviewed to determine the incidence of aneuploidy. Twenty nine pregnancies were registered, amongst which 12 (41%) had an abnormal karyotype, the most common aneuploidy being trisomy 21 (5 fetuses). The likelihood of aneuploidy increased with increasing thickness of the translucency. Where the karyotype was found to be normal, there was complete resolution of this ultrasound appearance by the second trimester in 15 of the 16 ongoing pregnancies: 9 have delivered normal neonates and 6 pregnancies are continuing. The other fetus developed evidence of a skeletal dysplasia by the second trimester.