Improved first-trimester Down syndrome screening performance by lowering the false-positive rate: a prospective study of 9941 low-risk women

OBJECTIVE

To determine the performance of screening for Down syndrome (DS) and other major chromosomal abnormalities using nuchal translucency (NT), free beta-human chorionic gonadotropin (beta-hCG) and pregnancy-associated plasma protein-A (PAPP-A) in a prospective study of a non-selected population.

METHODS

Of 9941 women with an early ultrasound examination, NT was measured in 8622 singleton pregnancies with a gestational age between 10 + 3 and 13 + 6 weeks. beta-hCG and PAPP-A were analyzed in 6441 cases. Detection rates (DR) and false-positive rates (FPR) for the NT screening, the double test (beta-hCG and PAPP-A) and the combined test (NT and the double test) were calculated using a 1 : 250 cut-off.

RESULTS

NT could be measured in 97.5% of cases. The DR for DS with NT screening alone was 75% with a FPR of only 1.8%. The double test detected 73% and the combined test 91%, for FPRs of 8.8% and 2.1%, respectively. We detected 80% of fetuses with other major chromosomal abnormalities with a combination of NT screening and other ultrasound findings. Low beta-hCG and PAPP-A values (below 0.4 MoM) were observed in 0.5% of the women including all cases of triploidy and trisomy 18 and 13.

CONCLUSIONS

The performance of a screening strategy for DS using a combination of NT and the double test was superior to that using either NT or the double test alone due to a very low FPR and a higher DR.

Late first-trimester invasive prenatal diagnosis: results of an international randomized trial

OBJECTIVE

To assess, in a randomized trial, the safety and accuracy of amniocentesis and transabdominal chorionic villus sampling (CVS) performed at 11-14 weeks of gestation, given that this time frame is increasingly relevant to early trisomy screening.

METHODS

We compared amniocentesis with CVS from 77 to 104 days of gestation in a randomized trial in a predominantly advanced maternal age population. Before randomization, the feasibility of both procedures was confirmed by ultrasonography, and experienced operators performed sampling under ultrasound guidance; conventional cytogenetic analysis was employed. The primary outcome measure was a composite of fetal loss plus preterm delivery before 28 weeks of gestation in cytogenetically normal pregnancies.

RESULTS

We randomized 3,775 women into 2 groups (1,914 to CVS; 1,861 to amniocentesis), which were comparable at baseline. More than 99.6% had the assigned procedure, and 99.9% were followed through delivery. In contrast to previous thinking, in the cytogenetically normal cohort (n = 3,698), no difference in primary study outcome was observed: 2.1% (95% confidence interval 1.5, 2.8) for CVS and 2.3% (95% confidence interval, 1.7, 3.1) for amniocentesis. However, spontaneous losses before 20 weeks and procedure-related, indicated terminations combined were increased in the amniocentesis group (P =.07, relative risk 1.74). We found a 4-fold increase in the rate of talipes equinovarus after amniocentesis (P =.02) overall and in week 13 (P =.03, relative risk = 4.65), but data were insufficient to determine this risk in week 14.

CONCLUSION

Amniocentesis at 13 weeks carries a significantly increased risk of talipes equinovarus compared with CVS and also suggests an increase in early, unintended pregnancy loss.

LEVEL OF EVIDENCE

I

Studies on the isolation and identification of fetal nucleated red blood cells in the circulation of pregnant women before and after chorion villus sampling

OBJECTIVE

To investigate the feasibility of various molecular forms of hemoglobin as markers for fetal nucleated red blood cells (NRBCs).

METHODS

The presence of epsilon and gamma globin positive NRBCs was investigated in pure fetal blood and in blood from pregnant women before and after chorion biopsy. Maternal samples were enriched for NRBCs by various conventional methods, including limited enrichment by only positive CD71 selection or single density gradient. We searched for fetal cells on slides by automated scanning. Fetal cells were defined by (1) the presence of epsilon or gamma globin and (2) simultaneously by the presence of a Y chromosome signal.

RESULTS

18 of 25 gamma globin positive cells identified in blood samples after chorion biopsy were chromosome Y signal positive, and 1 cell had two X chromosome signals. 263 of 339 epsilon globin positive cells identified in blood samples after chorion biopsy were hybridized with X and Y chromosome probes. None had two X signals, and 249 were Y positive. In blood samples before chorion biopsy, only 1 epsilon globin positive fetal NRBC and no epsilon globin positive maternal NRBCs were found.

CONCLUSIONS

Epsilon globin may be specific for fetal NRBCs. Only 1 epsilon globin positive fetal cell was identified in 1 of 12 blood samples before chorion biopsy, representing a total of 182 ml of maternal blood. This suggests that most fetal cells found in maternal blood by fluorescence in situ hybridization methods may not be NRBCs.

Treatment of severe fetal chylothorax associated with pronounced hydrops with intrapleural injection of OK-432

We describe a case of a 25-week fetus with severe bilateral pleural effusion, marked ascites, skin edema, an anterior thick (hydropic) placenta and polyhydramnios in which the most probable diagnosis was congenital chylothorax. Treatment with a pleuroamniotic shunt was planned, however the location of the fetus just below the anterior placenta made the placement of the shunt too dangerous. We therefore decided to use intrapleural injection of OK-432. From week 29, the lungs looked normal, the pleural effusion had resolved and the thoracic circumference was within normal limits. The severe ascites persisted throughout the pregnancy and a total volume of 3680 mL was removed on several occasions. A Cesarean section was performed at 38 weeks and a normal male was delivered. Continuous positive airway pressure was needed on the first 4 days but after a week the situation was stable. On day 8, an X-ray showed normally developed lungs. OK-432 appears to have prevented pulmonary hypoplasia in our patient.

zeta-, epsilon-, and gamma-Globin mRNA in blood samples and CD71(+) cell fractions from fetuses and from pregnant and nonpregnant women, with special attention to identification of fetal erythroblasts

BACKGROUND

Information about the appearance of gamma-, epsilon-, and zeta-globin mRNAs in fetal erythroblasts during gestation and about the presence and amounts of these mRNAs in pregnant and nonpregnant women is important from the perspective of using these molecules as a marker of fetal erythroblasts. A specific marker is necessary for isolation and identification of fetal nucleated red blood cells from maternal blood samples for use in antenatal diagnosis of fetal genetic or chromosomal abnormalities.

METHODS

We used a very sensitive reverse transcription-PCR (RT-PCR) method, coamplification analysis of gamma- and epsilon-globin cDNA, and quantitative analysis of gamma-globin mRNA based on competitive RT-PCR to investigate these aspects.

RESULTS

All adult whole-blood samples were negative for epsilon- and zeta-globin mRNA. Analyses of CD71(+) cell fractions showed that specimens from 19 of 20 nonpregnant and 10 of 14 pregnant women (at 9-13 weeks of gestation) were positive for gamma-globin mRNA (Fisher's exact test, P = 0.13), and those from 3 of 20 nonpregnant and 5 of 14 pregnant women were positive for zeta-globin mRNA (Fisher's exact test, P = 0.23). No epsilon-globin mRNA was detected in CD71(+) cell fractions from 1-mL blood samples from adults. CD71(+) cell fractions from eight fetal blood samples (at 17-20 weeks of gestation) were positive for all three globin mRNAs. We found no statistically significant difference between the amounts of gamma-globin mRNA in pregnant and nonpregnant women.

CONCLUSIONS

This study indicates that epsilon-globin mRNA might function as a marker for fetal CD71(+) cells early in pregnancy. Although gamma-globin mRNA can be detected in CD71(+) cell fractions from most adults, these transcripts also may be of use because of a marked difference between adult and fetal values.

Sex differences in response to red and blue light in human primary visual cortex: a bold fMRI study

Studies using a variety of investigative methods, including functional brain imaging and electroencephalography (EEG), have suggested that changes in central nervous system (CNS) dopamine function result in altered visual system processing. The discovery of abnormal retinal blue cone, but not red cone, electroretinogram in association with cocaine withdrawal and Parkinson's disease suggests that visual system response to blue light might be a marker for CNS dopamine tone. As there are numerous sex-related differences in central nervous system dopamine function, we predicted that blue and red light stimulation would produce sex-specific patterns of response in primary visual cortex when studied using the blood oxygen level dependent (BOLD) functional magnetic resonance imaging (fMRI) technique. We analyzed the BOLD response to red and blue light in male and female human volunteers (N=20). Red and blue light responses in primary visual cortex (V1) to stepped intensities of red and blue light were compared by sex for threshold to detectable BOLD signal increase and for stimulus intensity vs. BOLD signal response. Near threshold, males and females showed similar BOLD signal change to red light, but males showed a threefold greater increase (0.52%) to blue light stimulation when compared to females (0.14%). Log-linear regression modeling revealed that the slope coefficients for the red light stimulus intensity vs. signal change curve were not significantly different for males and females (z=0.995, P=0.320), whereas the slope coefficients for the blue light stimulus intensity vs. signal change curve were significantly larger in males (z=2.251, P=0.024). These findings support a sex and color-dependent differential pattern of primary visual cortical response to photic stimulation and suggest a method for assessing the influence of specific dopamine agonist/antagonist medications on visual function.

[Selective foeticidium using YAG laser]

Twin-to-twin transfusion syndrome was found by ultrasound in monochorionic diamniotic twins in week 20. The donor had hydrocephalus and the recipient was normal. Selective foeticide was performed by coagulating the vessels of the umbilical cord of the donor with a YAG-laser. The pregnancy continued without complications and a healthy girl was born in week 34. The birth weight was 2935 g. Psychomotor development was normal at the age of six months.

MULTISCAN--a Scandinavian multicenter second trimester obstetric ultrasound and serum screening study

AIM

To study the detection rates of second trimester ultrasound screening for neural tube defects (NTD), abdominal wall defects (AWD) and Down's syndrome (DS) in low risk populations at tertiary centers, and to compare the ultrasound screening detection rates with those that were obtainable by biochemical serum screening (double test: alpha-fetoprotein/human chorion gonadotrophin/age test).

STUDY DESIGN

Prospective multicenter study with a three year inclusion period: 1/1/1989-31/12/1991.

SUBJECTS

27,844 low-risk women at 18-34 years of age who had a second trimester ultrasound screening examination. Of these, 10,264 also had a serum test.

METHODS

An ultrasound malformation scan and a serum test were carried out at 17-19 weeks of gestation. Risk calculations regarding DS were based on alpha-fetoprotein, human chorion gonadotrophin and maternal age; performed retrospectively for the first two years.

RESULTS

In total 73 cases were identified in the study population: NTD (n=34), AWD (n=7) and DS (n=32). The detection rates, (%, with 95% confidence interval) for ultrasound screening were: NTD: 79.4 (62.1-91.3); AWD: 85.7 (42.1-99.6); DS: 6.3 (0.8-20.8). In the subgroup of women who had both tests, the detection rates for ultrasound screening vs double test were: NTD: 62.5 (24.5-91.5) vs 75.0 (34.9-96.8); AWD: 66.7 (9.4-99.2) vs 100 (29.2-100.0); DS: 7.7 (0.2-36.0) vs 46.2 (19.2-74.9). The false positive rates (%) for ultrasound screening vs double test were: NTD: 0.01/3.3; AWD: 0.01/3.3; DS: 0.1/4.0.

CONCLUSION

Second trimester ultrasound screening in a low risk population gave a low detection rate for fetal DS (6.3%) and an acceptable detection rate for NTD (79.4%) and AWD (85.7%). In the subgroup of women who had both tests, serum screening performed better than ultrasound as applied in the present study, especially regarding DS.

Randomised study of risk of fetal loss related to early amniocentesis versus chorionic villus sampling

BACKGROUND

Several cohort studies have shown the feasibility of early amniocentesis (between 11 and 13 weeks of gestation) as an alternative to chorionic villus sampling (CVS) for karyotyping, but the only completed randomised study of fetal safety showed a significant fetal-loss risk related to first-trimester amniocentesis. We assessed fetal safety in early amniocentesis and CVS.

METHODS

We assessed early amniocentesis at 11-13 weeks gestational age compared with the fetal risk associated with CVS at 10-12 weeks. 1160 pregnant women were randomly assigned one procedure (581 early amniocentesis, 579 CVS) after a baseline ultrasound examination at 10 weeks' gestation and were followed up until birth. Total fetal loss and neonatal morbidity were the primary outcome measures. Sampling success and pregnancy complications were secondary outcomes. We used a filter to increase the cell yield in the early amniotic-fluid samples. CVS was transabdominal.

FINDINGS

We found a significantly increased occurrence of talipes equinovarus in the early amniocentesis group (p < 0.01), the risk of which was associated with sampling at the earliest gestational ages and with temporary leakage of amniotic fluid after sampling. Therefore, the trial was stopped early, which reduced the power of the safety study. 4.8% (27) of fetuses in the CVS group and 5.4% (30) in the early amniocentesis group were lost after randomisation (p = 0.66). More detailed survival analysis did not show any significant differences in fetal loss rates. Leakage of amniotic fluid after sampling occurred significantly more frequently after early amniocentesis than after CVS (p < 0.001), but we found no other major differences in pregnancy complications. Significantly more CVS than early amniocentesis procedures were repeated or failed to produce a karyotype (p < 0.01).

INTERPRETATION

Even though the numbers were small, we found an association between early amniocentesis and talipes equinovarus. We believe this association to be true, since it supports a trend in a similar randomised study. Our results show that early amniocentesis, when done with the filter technique, is associated with an abortion risk similar to CVS, although the limited size of our study population reduced the strength of this conclusion.

Bilateral stress-fracture of the calcaneal tubercle

A case of bilateral stress fracture of the calcaneal tubercle (beak-fractures) in a 67-year-old woman is presented. The pathogenesis and treatment are discussed, followed by some general considerations on stress fractures.

Prenatal detection of chromosome aneuploidies in uncultured chorionic villus samples by FISH

We developed a 1-d FISH assay for detection of numerical chromosome abnormalities in uncultured chorionic villus samples (CVS). Probes specific for chromosomes 13, 18, 21, X, and Y were used to determine ploidy by analysis of signal number in hybridized nuclei. Aneuploidy detection using this assay was directly compared with the results obtained by conventional cytogenetic analysis in a consecutive, clinical study of 2,709 CVS and placental samples. The FISH assay yielded discrete differences in the signal profiles between cytogenetically normal and abnormal samples. On the basis of these results, we generated FISH-assay cutoff values that discriminated between karyotypically normal and aneuploid samples. Samples with mosaicism and a single sample with possible heritable small chromosome X probe target were exceptions and showed poor agreement between FISH results and conventional cytogenetics. We conclude that the FISH assay may act as a more accurate and less labor-demanding alternative to "direct" CVS analysis.

Early sonographically guided amniocenteses with filtration technique: follow-up on 249 procedures

Fetal and neonatal outcome is reported for 249 consecutive low-risk pregnancies in which early amniocentesis was carried out with filter technique, at a mean gestational age of 12.5 weeks, to improve the yield in cell cultures. Three pregnancies (1.2%) were terminated because of abnormal test results, four stillbirths (1.6%) occurred between weeks 33 and 38, and five pregnancies were lost spontaneously after sampling, corresponding to 2% of unintended fetal losses before 28 weeks of gestation. Of the live-born infants, 2.9% were delivered prematurely, all between weeks 32 and 37. Malformations and orthopedic postural deformities were not associated with leakage after amniocentesis and were found at expected rates. None of the cases was lost to follow-up. The increase in abortion rate caused by early amniocentesis with filter technique is likely to be within the same range as that seen after routine amniocentesis and transabdominal chorionic villus sampling, although the sample is too small for a proper risk evaluation.

[Spontaneous avulsion of the tibial tuberosity following Osgood-Schlatter disease]

Two cases of spontaneous fracture and dislocation of the tibial tuberosity in boys (15 and 19 years of age), who had both suffered from Osgood-Schlatter disease are described. The treatment and prognosis are discussed.

Experience with early amniocentesis

Literature concerning early genetic amniocentesis, obtained before 14-15 weeks of gestation, has been examined and compared. Key figures of post-procedural spontaneous fetal losses have been compared as well as cytogenetic data from the published series. Cytogenetically more samples fail to grow in the early weeks, but the diagnostic accuracy seems to be comparable with that of amniocentesis obtained in the later weeks. A sampling method, improving the cell yield by means of filtration, has been developed in order to lower the risk of culture failure and reduce the reporting time in the gestational weeks 11 to 13. The filter technique is under evaluation in a randomized trial. Detection of neural tube defects with early amniotic fluid sampling is possible, but whether the detection rate is comparable to that of standard amniocentesis remains to be seen. Although the safety of early amniocentesis has not yet been evaluated in a randomised study, data from almost 5,000 cases suggest that the procedure related loss rate is approximately 1%, and thus the same as for standard amniocentesis and chorionic villus sampling.

Early prenatal direct gene diagnosis of cystic fibrosis in a twin pregnancy and subsequent selective termination

We present a case of prenatal diagnosis of cystic fibrosis (CF) in one twin at 11-12 weeks of gestation. The parents had previously had two children, one of whom is alive and healthy and one who died of CF at the age of 2 1/2 months. The parents were both known to be carriers of the delta F508 mutation. Chorionic villus sampling (CVS) was performed and direct gene analysis showed that one fetus was homozygous for the delta F508 mutation, while the other fetus did not have the mutation at all. Both fetuses had normal karyotypes. Selective termination was subsequently performed. The pregnancy continued without complications except for mild pre-eclampsia at term. The woman had a Caesarean section. The genetic diagnosis was confirmed after birth.

Current status of research on biophysical effects of ultrasound

This overview of bioeffects of ultrasound presents some key aspects of selected papers dealing with biophysical end-points. Its purpose is to establish a basis for exposure and dosimetric standards for medical ultrasonic equipment. It is intended to provide essential background resource material for the medical/scientific community, and more specifically for scientific working groups. This document was prepared by members of the Safety Committee of the World Federation for Ultrasound in Medicine and Biology. It was produced as a resource document in response to a request for information by Working Group 12 (Ultrasound exposure parameters) of the International Electrotechnical Commission Technical Committee 87, Ultrasonics. IEC TC 87, WG12 is the working group responsible for generating international standards for the classification of equipment by its acoustic fields based on safety thresholds. Our paper is intended to update and supplement information on the thermal mechanism provided in the publication, "WFUMB Symposium on Safety and Standardisation in Medical Ultrasound: Issues and Recommendations Regarding Thermal Mechanisms for Biological Effects of Ultrasound" (WFUMB 1992). It also provides an overview of trends in research into nonthermal mechanisms as a preliminary to the next WFUMB Symposium on Safety of Medical Ultrasound when this subject will be examined in detail by a select group of international experts. The WFUMB-sponsored workshop will take place in Utsunomiya, Japan during 11-15th July, 1994. The purpose of the meeting is to evaluate the scientific literature and to formulate internationally accepted recommendations on the safe use of diagnostic ultrasound that may be endorsed as official policy of the WFUMB. It should be noted that the current publication is not intended for review or endorsement as an official WFUMB document. It is produced as a scientific paper by individuals who are members of the WFUMB Safety Committee, and it therefore represents the opinions of the authors. Nevertheless, during the preparation of this document, contributions were received from members of the International Electrotechnical Commission Technical Committee 87 as well as many other individual experts, and the authors sincerely acknowledge their support.

[Early amniocentesis]

Genetic amniocentesis performed at 7-14 weeks of gestation was studied in a series of 138 patients of whom 50 wanted termination of pregnancy (< or = 12 weeks). The material for analysis consisted of 132 samples due to two sampling failures and four samples being handled incorrectly. Forty-eight samples (36 percent) were taken at 7-12 weeks of gestation, mainly transvaginally (36/48:75 percent). The success rate of culture and karyotyping increased with the duration of pregnancy, but was only satisfactory from week 11 onwards. The time until harvest was then 14-15 days. The transvaginal approach is easy to perform and was accepted by the women, but we experienced bacterial or fungal overgrowth in 17 percent of these samples, whereas no infection occurred in the samples taken transabdominally (n = 96). We conclude that genetic amniocentesis is feasible from week 11, but further studies concerning side effects, especially focusing on the procedure-related abortion risk, should be carried out before early amniocentesis is routinely applied.

Genetic amniocentesis at 7-14 weeks of gestation

Genetic amniocentesis performed at 7-14 weeks of gestation was studied in a series of 138 patients of whom 50 wanted termination of pregnancy (less than or equal to 12 weeks). The material for analysis consisted of 132 samples due to two sampling failures and four samples being handled incorrectly. Forty-eight samples (36 per cent) were taken at 7-12 weeks of gestation, mainly transvaginally (36/48: 75 per cent). The success rate of culture and karyotyping increased with the duration of pregnancy, but was only satisfactory from week 11 onwards. The time until harvest was then 14-15 days. The transvaginal approach is easy to perform and was accepted by the women, but we experienced bacterial or fungal overgrowth in 17 per cent of these samples, whereas no infection occurred in the samples taken transabdominally (n = 96). We conclude that genetic amniocentesis is feasible from week 11, but further studies concerning side effects, especially focusing on the procedure-related abortion risk, should be carried out before early amniocentesis is routinely applied.

Early prenatal diagnosis of the fragile site at Xq27.3 associated with Martin-Bell syndrome

Early prenatal diagnosis of the fragile X was attempted in 44 pregnancies, including one twin pregnancy at risk of Martin-Bell (MB) syndrome. The sex ratio was 24M:21F. The fragile site was reproducibly demonstrated in cultured chorionic villus (CV) cells in eight male and five female fetuses. Six of the male and three of the female fetuses were terminated. Simultaneous RFLP analysis provided confirmative data with flanking DNA markers in 3 of 13 analysed cases. Recombination and/or non-informativeness at available distal and/or proximal loci were found in nine cases. In one male fetus, discordance between the haplotype and cytogenetics (fragile-X-negative) suggested the presence of a normal male transmitter, a double meiotic cross-over within the region, or a false-negative cytogenetic diagnosis. However, discordance between prenatal and post-termination/postnatal cytogenetic findings was not observed in this series. The use of excess thymidine for induction of the fragile X in cultured CV cells provided in the majority of cases a safe and rapid method for cytogenetic diagnosis, with options for early induced termination in fragile-X-positive pregnancies, for simultaneous RFLP analysis, and for subsequent second-trimester analysis of fetal blood in complicated cases.

Routine examination by ultrasound for the detection of fetal malformations in a low risk population

A low risk population was offered screening for malformations in the second and third trimesters of pregnancy. Of 16,763 scans of pregnancies in the second trimester, 61 malformations were identified (0.36%). In the third trimester, scanning of 10,752 pregnancies revealed 24 malformations (0.22%): in all, in a low risk population 0.58% major malformations were found. The sensitivity for noncardiac malformations of the second trimester scanning was 54.3 with a specificity of 99.9%. The malformations overlooked was a more benign spectrum than the cases diagnosed. The sensitivity for cardiac malformations was less than 20%.

Dyssegmental dysplasia in siblings: prenatal ultrasonic diagnosis

Two cases of dyssegmental dysplasia (type Silverman-Handmaker) in siblings are presented. The first-born died at the age of 3 months and the second fetus was followed during pregnancy with ultrasound examinations. In the 20th week of gestation marked shortening of the extremities was found; a female infant showing the same radiologic bony malformations as the firstborn was born by cesarean section. These cases support the autosomal recessive inheritance and demonstrate the possibility of prenatal diagnosis in this type of micromelic dwarfism.