Chromosomal prenatal diagnosis: Study of 936 cases of intrauterine abnormalities after ultrasound assessment

Nine hundred and thirty-six prenatal chromosomal analyses were performed by four cytogenetic centres after ultrasound diagnosis of fetal abnormalities, amniotic fluid disorders, fetal growth retardation, and fetal or placental abnormalities. During the same period, 6515 fetal karyotypes were analysed because of maternal age. Frequencies of chromosomal aberrations in each case were respectively 4·4, 6·7 and 15·8 per cent, compared with 3·18 per cent when the fetal karyotype was performed because of maternal age. High rates of chromosomal aberrations are observed in cases of cervical hygroma, limb abnormalities, omphaloceles, duodenal stenosis, hydrocephalus, and facial abnormalities. In the case of polymalformations, this rate was 29·2 per cent. When malformations were seen together with an amniotic fluid disorder or growth retardation, 21·5 per cent chromosomal aberrations were observed. This frequency was 10·4 per cent when growth retardation was associated with an amniotic fluid disorder. Trisomy 13, 18, 21 and monosomy X accounted for 4/5 of all abnormalities in which we observed a high rate of triploidies (4·9 per cent) and balanced (3·3 per cent) or unbalanced (9·8 per cent) non-Robertsonian structural abnormalities. Sonographic ascertainment of these aberrations and prenatal characteristics of major anomalies are discussed.     

Prenatal karyotyping in malformed fetuses

Experience with prenatal karyotyping of 237 fetuses with sonographic evidence of malformation is reported. Abnormal karyotype was found in 40 cases (16-8 per cent): chromosomal aberrations were found in 19 of the 178 fetuses with an isolated structural anomaly (10-6 per cent) and in 21 of the 59 fetuses with multiple malformations (35-6 per cent). Detailed cytogenetic and morphological information concerning fetuses affected by omphalocele, duodenal atresia, hydrocephalus, multicystic kidney, unilateral hydronephrosis and cystic hygroma is reported. The need for a very careful ultrasound evaluation of fetal anatomy in these pregnancies is stressed, as the risk of a chromosomal anomaly depends mainly on the existence of more than one ultrasonically diagnosed structural defect.     

Cystic Adenomatoid malformation of the lung: Prenatal diagnosis and outcome

During an 8-year period (1984–1992), we made the ultrasonographic diagnosis of cystic adenomatoid malformation (CAM) of the lung in 58 fetuses at 17–39 weeks' gestation. We reviewed the records of these fetuses and combined the data from 74 cases reported in the literature to determine the incidence of the different types of CAM, associated malformations, and outcome. The lesions were macrocystic in 78 (59 per cent) and microcystic in 54 (41 per cent) of the cases. CAM was left-sided in 51 per cent, right-sided in 35 per cent, and bilateral in 14 per cent of the fetuses. In 15 (11 per cent) of the fetuses there were additional malformations and 57 (43 per cent) were hydropic. The pregnancy was electively terminated in 44 (33 per cent) of the cases, including all those with bilateral CAM. There were six (5 per cent) intrauterine deaths, five in association with hydrops, and one with growth retardation and heart defect. Of the 82 (62 per cent) infants that were liveborn, 21 (26 per cent) died in the neonatal period, 15 before and six after surgery. Of the 61 survivors, 16 (26 per cent) did not require surgery. In the 88 cases where the pregnancy was not terminated, survival was better if the CAM was macrocystic (74 per cent versus 58 per cent for microcystic), if there was no hydrops (92 per cent versus 21 per cent for hydrops), and if the amniotic fluid volume was normal or decreased (82 per cent versus 53 per cent for polyhydramnios).     

Cystic hygroma: Prenatal diagnosis and genetic counselling

Six cases of cystic hygromas detected during second trimester ultrasound examination are reported: 4 fetuses (67 per cent) had a 45, X karyotype, 1 fetus had trisomy 18, 1 fetus had a normal karyotype (46,XX) and at autopsy multiple anomalies were observed. In the latter case the family history suggested an autosomal recessive pattern of inheritance. In order to reach a definite diagnosis and give proper genetic counselling when a fetus is found to have cystic hygroma, a fetal karyotype as well as a family and reproductive history should be obtained.     

Significance of septations in isolated fetal cystic hygroma detected in the first trimester

Recent reports have indicated an increased risk for fetal chromosome abnormalities, especially autosomal trisomy, in fetuses with isolated cystic hygroma, or prominent nuchal membranes, detected by ultrasonography during the first trimester. However, these reports present contradictory information regarding the prognostic significance of septations within the cystic hygroma. We evaluated, in blind fashion, 55 consecutive cases of isolatd fetal cystic hygroma detected at or before 13·9 weeks' gestation to determine the association between septations and fetal chromosome complement. Septations were associated (P<0·05) with an increased risk for fetal chromosome abnormalities. However, the incidence of chromosome abnormalities was also increased (12·5 per cent) among cases not characterized by septations. Thus, we believe it prudent to offer invasive prenatal testing to all women found to be carrying fetuses with cystic hygroma, irrespective of the presence or absence of septations.     

Complications of cordocentesis in high-risk pregnancies: Effects on fetal loss or preterm delivery

Between 1990 and 1993, 166 cases underwent cordocentesis and were followed for at least the following 4 weeks in the Prenatal Diagnosis and Therapy Centre of Vienna University. The indications for the procedure were structural malformations in 46·4 per cent of the cases, other high-risk diagnoses in 48·8 per cent, and maternal age over 35 years in only 4·8 per cent. We investigated retrospectively all cases of complications resulting in fetal loss or preterm labour. Abortion, intrauterine fetal death, chorioamnionitis, and preterm delivery occurred in 0·6, 5·4, 0·6 and 9·0 per cent of these cases, respectively, adding up to a total of 26 cases (15·7 per cent). Although this rate looks relatively high, 20 of the 26 cases had already displayed signs implying a complicated prognosis. Neither maternal age, gestational age, number of attempts, nor placental location correlated with fetal loss or preterm delivery. Significantly higher rates of fetal loss or preterm delivery were observed when cordocentesis was performed in cases diagnosed as duodenal/intestinal stenosis or hydrops–ascites–hydrothroax/hygroma colli (P=0·0488 and P=0·0005). The frequency of complications did not decrease as the experience of the operators increased.     

Amniotic fluid-AFP in Down syndrome and other chromosome abnormalities

80·2 Per cent of 111 Down syndrome pregnancies had amniotic fluid (AF) alpha fetoprotein (AFP) levels on or below the median and 10·8 per cent at or below 0·5 MoM compared with 41·9 and 1·4 per cent of controls. These differences were even more striking when the gestational age was < 18 weeks compared with ⩾ 18 weeks. No such association was seen for other chromosome abnormalities including trisomy 18,45,X and mosaics, 47,XXY, 47,XXX, and other structural abnormalities and triploidy, even when high levels due to defects such as omphalocele and cystic hygroma were excluded. All cases of trisomy 13 and 80 per cent with 47,XYY had AF-AFP levels above the median. Selection of cases for karyotyping by a low level of AF-AFP would clearly fail to detect aneuploidies other than Down syndrome and is not recommended. A possible weak association between low maternal serum (MS) and AF-AFPs in Down syndrome was most evident at < 18 weeks, suggesting that MS screening between 16 and 18 weeks may be the most informative time.     

Diagnosis of polyhydramnios in early gestation: Indication for prenatal diagnosis?

Previously published reports have indicated that idiopathic polyhydramnios may be associated with trisomies 18 and 21 and that chromosomal analysis is indicated. Furthermore, the natural history and fetal outcome of polyhydramnios diagnosed in early gestation have not been well delineated. We identified 138 pregnancies with polyhydramnios prior to 26 weeks' gestation. Of 131 complete cases, 21 were diagnosed as severe, 18 as moderate, and 92 as mild polyhydramnios. Congenital abnormalities were noted in 18 of 21 severe cases (86 per cent). Two of the remaining three cases were twin-to-twin transfusion. Thirteen of 18 cases with moderate polyhydramnios (72 per cent) were associated with anomalies; six of the remaining cases were twin-to-twin transfusion. Sixteen of 92 cases of mild polyhydramnios (17 per cent) were associated with congenital abnormalities. In 69 of 76 cases of mild hydramnios not associated with anomalies (91 per cent), the hydramnios resolved prior to delivery. Only 2 of 16 (13 per cent) associated with anomalies resolved. In 4 of 5 cases (80 per cent) with moderate hydramnios and no anomalies, the amniotic fluid volume was normal on subsequent ultrasound. No case of moderate polyhydramnios associated with anomalies or maternal conditions nor any case of severe polyhydramnios resolved. There were seven cases of chromosomal abnormalities in this series; all were associated with sonographic findings in addition to the presence of polyhydramnios. On the basis of these data, we doubt the benefit of amniocentesis following the early diagnosis of idiopathic polyhydramnios in the absence of other ultrasound findings.     

Prenatal diagnosis of turner syndrome using cells cultured from cystic hygromas in two pregnancies with normal maternal serum alpha-fetoprotein

In two cases of prenatally detected cystic hygroma with oligohydraminos, successful cytogenetic diagnosis of Turner syndrome was achieved using cells obtained from direct aspiration of the cystic hygroma. Exceptionally high levels of alpha-fetoprotein were found in the cystic hygroma fluid, as might be expected. However, the maternal serum alpha-fetoprotein levels were within normal limits. Elevated alpha-fetoprotein levels in ‘amniotic fluid’ noted previously in the literature may have resulted because of inadvertent tapping of the cystic hygroma. It is clear from our cases that maternal serum levels of alpha-fetoprotein will not necessarily be elevated and will not serve as a screening mechanism for cystic hygromas.     

Prenatal detection of trisomy 21 in uncultured amniocytes by fluorescence in situ hybridization: A prospective study

A prospective study was undertaken to evaluate the use of fluorescence in situ hybridization (FISH) for the detection of trisomy 21 in interphase nuclei of uncultured amniotic fluid cells. Five hundred cases were analysed in situ and classified as normal or abnormal; the results were subsequently checked against the cytogenetic findings. Four hundred and ninety-three were correctly identified as normal with an 86·6 per cent average frequency of scored nuclei exhibiting two signals; six cases were correctly identified as trisomic for chromosome 21 with 81·7 per cent of scored nuclei exhibiting three signals; and one abnormal case involving an unbalanced chromosome 21·21 translocation was falsely scored as normal due to poor hybridization/detection efficiency. The method has been substantially improved and simplified so that it is suitable for the rapid detection of trisomy 21. As aneuploidy detection in interphase does not identify structural chromosome aberrations, it is not a substitute for fetal chromosome analysis.     

Serum PAPP-A and free β-hCG are first-trimester screening markers for down syndrome

Serum measurements of pregnancy-associated plasma protein A (PAPP-A) and the free β-human chorionic gonadotrophin (hCG) subunit were made in 13 women with Down syndrome (DS) pregnancies and six other women with fetal aneuploidy ascertained at chorionic villus sampling (CVS), as well as 89 women with contemporaneous normal control pregnancies. Median serum PAPP-A measurements (0·31 MOM, 95 per cent confidence interval (CI) 0·22–0·65 vs. normal 1·06, 95 per cent CI 0·89–1·20) were lower and free β-hCG subunit measurements (1·13 MOM, 95 per cent CI 0·93–2·63 vs. normal 0·91, 95 per cent CI 0·79–1·03) were higher at statistically significant levels. Receiver operator characteristic (ROC) curves showed that the highest sensitivity for detection, 71·2 per cent (95 per cent CI 54·7–87·6 per cent), was for depressed PAPP-A levels; the combination of low serum PAPP-A levels, maternal age, and elevated free β-hCG levels yielded a detection rate of 78·9 per cent (95 per cent CI 64·9–92·8 per cent) of the affected pregnancies at 8–12 weeks' gestation.     

Amniotic fluid alpha-fetoprotein,gamma-glutamyltranspeptidase,and autosomal trisomies

Alpha-fetoprotein (AFP) concentration and gamma-glutamyltranspeptidase (GGT) activity have been analysed in amniotic fluid from a series of 65 pregnancies with autosomal trisomies. AFP values were reduced on average to 60 per cent of normal in cases of trisomy 21, but were not significantly different from normal in cases of trisomies 18 and 13. GGT activities were uniformly lower (44 per cent of normal) for all types of autosomal trisomy. A review of the literature indicates that over 85 per cent of Down's pregnancies but only 39 per cent of trisomy 18 and 13 pregnancies have amniotic fluid AFP levels below the normal median value, while the corresponding figures for GGT are 91 per cent for Down's syndrome and 96 per cent for trisomies 18 and 13.     

Cytogenetic results from the U.S. collaborative study on CVS

Cytogenetic data are presented for 11 473 chorionic villus sampling (CVS) procedures from nine centres in the U.S. NICHD collaborative study. A successful cytogenetic diagnosis was obtained in 99.7 per cent of cases, with data obtained from the direct method only (26 per cent), culture method only (42 per cent), or a combination of both (32 per cent). A total of 1.1 per cent of patients had a second CVS or amniocentesis procedure for reasons related to the cytogenetic diagnostic procedure, including laboratory failures (27 cases), maternal cell contamination (4 cases), or mosaic or ambiguous cytogenetic results (98 cases). There were no diagnostic errors involving trisomies for chromosomes 21, 18, and 13. For sex chromosome aneuploidies, one patient terminated her pregnancy on the basis of non-mosaic 47,XXX in the direct method prior to the availability of results from cultured cells. Subsequent analysis of the CVS cultures and fetal tissues showed only normal female cells. Other false-positive predictions involving non-mosaic aneuploidies (n = 13) were observed in the direct or culture method, but these cases involved rare aneuploidies: four cases of tetraploidy, two cases of trisomy 7, and one case each of trisomies 3, 8, 11, 15, 16,20, and 22. This indicates that rare aneuploidies observed in the direct or culture method should be subjected to follow-up by amniocentesis. Two cases of unbalanced structural abnormalities detected in the direct method were not confirmed in cultured CVS or amniotic fluid. In addition, one structural rearrangement was misinterpreted as unbalanced from the direct method, leading to pregnancy termination prior to results from cultured cells showing a balanced, inherited translocation. False-negative results (n = 8) were observed only in the direct method, including one non-mosaic fetal abnormality (trisomy 18) detected by the culture method and seven cases of fetal mosaicism (all detected by the culture method). Mosaicism was observed in 0.8 per cent of all cases, while pseudomosaicism (including single trisomic cells) was observed in 1.6 per cent of cases. Mosaicism was observed with equal frequency in the direct and culture methods, but was confirmed as fetal mosaicism more often in cases from the culture method (24 per cent) than in cases from the direct method (10 per cent). The overall rate of maternal cell contamination was 1.8 per cent for the culture method, but there was only one case of incorrect sex prediction due to complete maternal cell contamination which resulted in the birth of a normal male. The rate of maternal cell contamination was significantly higher in samples obtained by the transcervical sampling method (2. 16 per cent) than in samples obtained by the transabdominal method (0.79 per cent). From these data, it is clear that the culture method has a higher degree of diagnostic accuracy than the direct method, which should not be used as the sole diagnostic technique. The direct method can be a useful adjunct to the culture method, in which maternal cell contamination can lead to incorrect sex prediction and potentially to false-negative diagnostic results.     

Placental mosaicism in a case of 46,XY, −22, +t(22;22)(p11;q11) or i(22q) diagnosed at amniocentesis

46,XY, −22,+t(22;22)(p11;q11) or i(22q) was diagnosed in 15/15 cells from two cultures from the amniotic fluid culture of a 31-year-old patient whose fetus demonstrated cystic hygroma on ultrasound. Cytogenetic studies performed on fetal skin from the abortus revealed the same karyotype as that seen on amniocentesis, but the placenta demonstrated a 46,XY,46,XY, −22,+t(22;22) or i(22q) mosaicism, with 65 per cent of the cells being 46,XY. This case provides an example of placental mosaicism for a normal male karyotype, while the fetus demonstrated non-mosaic trisomy 22.     

Short communication kazal type trypsin inhibitor in amniotic fluid in fetal developmental disorders

The amniotic fluid concentrations of the Kazal type trypsin inhibitor were studied in pregnancies with fetal developmental disorders. The samples were obtained by amniocentesis between 14 and 19 weeks of gestation. In cases with fetal malformations, the level was below the normal 10th centile in 15 out of 28 cases (54 per cent, P<0.05) and above the normal 90th centile in 2 cases (7.1 per cent). Low values were common in cases with intrauterine fetal death or congenital nephrosis. The levels were normal in fetal chromosomal aberrations.     

Prenatal ultrasonic diagnosis of obstructive bowel disease: A retrospective analysis

Fetal obstructive bowel disease was diagnosed in 29 patients at 22–37 weeks (median 32 weeks) of gestation, seven (24 per cent) of whom also displayed other anomalies. Polyhydramnios was present in 20/29 cases (69 per cent). An abnormal karyotype existed in 7/29 cases (24 per cent), of which six were diagnosed prenatally (trisomy 21, n = 5; 69, XXX, n = 1) and one postnatally (trisomy 21). There was always an association with the ultrasonic ‘double bubble’ sign. Obstructive bowel disease was confirmed postnatally in 20/29 (69 per cent) cases, i.e., oesophageal atresia (n = 1), duodenal obstruction (n = 12), and small bowel obstruction (n = 7). Other anomalies existed in 6/29 (21 per cent) cases, i.e., multicystic kidney (n = 1) and multiple congenital anomalies (n = 5). The perinatal mortality rate was 35 per cent (7/20).     

Fetal renal artery flow velocity waveforms in the presence of congenital renal tract anomalies

Colour Doppler flow mapping of the renal arteries and subsequent pulsed Doppler measurement of impedance to flow in these vessels were attempted in 33 fetuses with postnatally confirmed renal pathology. The majority presented with unilateral or bilateral hydronephro-sis (n = 21) and bilateral renal agenesis (n = 8). Renal artery blood flow could be visualized in all, except for the eight cases of bilateral renal agenesis. Bilateral flow velocity recordings were collected in six out of 12 cases of bilateral hydronephrosis and in five out of nine cases of unilateral hydronephrosis. The pulsatility index (PI), as a measure of downstream impedance, was in the normal range in 16 out of 18 kidneys (88 per cent) in bilateral hydronephrosis and in 12 out of 14 kidneys (85 per cent) in unilateral hydronephrosis. The PI was significantly higher in severe hydronephrosis compared with mild hydronephrosis. In four cases of unilateral multicystic kidney, the PI was always higher on the affected side. Colour Doppler flow mapping and pulsed Doppler evaluation may be helpful in our understanding of renal vascularization in renal pathology and in confirming the diagnosis of renal agenesis.     

Feto-amniotic shunting—report of the experience of four european centres

Few reports concerning intrauterine shunting are available. We investigated the impact of this method. In order to evaluate intrauterine shunting and the complication rate for different indications, we sent a questionnaire to all German-speaking level 3 centres. In four level 3 centres, 52 intrauterine catheters were inserted in 34 fetuses. The indications were uni- or bilateral hydrothorax in nine cases, cystic adenomatoid malformation of the lung in four cases, infravesical stenosis in 13 cases, and fetal ascites in eight cases. In three cases (6 per cent), difficulties occurred when the drain was inserted. In 15 cases (29 per cent), the function of the drain was reduced by dislocation or occlusion. The mortality rate caused by shunting was as high as eight per cent (four cases). The application of an intrauterine shunt currently represents a rarely performed ultrasound-guided therapeutic intervention in the fetus. In all cases, the indication for shunting is to avoid compression of normal tissue by cystic structures. A high complication rate restricts the application of drainage to selected cases.     

Chromosome analysis of multipronuclear human oocytes after in vitro fertilization

Multipronuclear human eggs are frequent after in vitro fertilization. Their chromosome analysis can provide useful information. Before cleavage it can confirm the suspected poly-ploidy. Among the cleaved multipronuclear eggs it provides an estimation of the incidence of the possible return to diploidy. Ninety-four multipronuclear eggs were fixed at the first, second, or third cleavage according to the air-drying method of Tarkowski with or without colchicine exposure: 60 were successfully analysed. Twelve were stopped before cleavage (six without colchicine treatment and six with colchicine treatment). They were polyploid, confirming the cytological observation. Forty-eight eggs cleaved and were stopped by colchicine treatment and karyotyped. Seventeen eggs (35 per cent) had produced diploid embryos. Mosaicism was frequent (15 cases, 31 per cent). Triploidy was not frequent (8 eggs, 17 per cent). Haploidy constituted the remaining cases (8 eggs, 17 per cent). Our data indicate that the initial count of pronuclei is a reliable test. Multipronuclear one-cell oocytes were confirmed to be polyploid. Furthermore, the developmental capacity of the multipronuclear oocytes is variable. Most of them cleaved. However, many multipronuclear oocytes led to diploid cleaving eggs.     

Risk of miscarriage after transcervical and transabdominal CVS in relation to bacterial colonization of the cervix

Cervieo-genital colonization with micro-organisms poses a potential threat to the pregnancy when transcervical (TC) CVS is performed. In order to evaluate this threat, cervical swabs in 478 patients were obtained and cultured for bacteria, yeasts, and mycoplasmas; chlamydias were detected by an enzyme immunology test. Two hundred and seventy-one patients had CVS (ione transvaginally and 207 underwent transabdominal (TA) CVS. Transvaginal specimens were obtained in 61.6 per cent by forceps biopsy. Overall in 29.9 per cent of patients micro-organisms were detected, the rate and distribution of different species being the same in both groups. There were 36 (7.5 per cent) miscarriages up to 28 weeks of gestation in the combined groups, 29 (10.7 per cent) in the TC-CVS group and 7 (3.4 percent) in the TA-CVS group. When miscarriages occurred after TC-CVS, bacteria/yeasts were involved in 10.3 per cent cif cases and mycoplasmas in 37.9 per cent, this proportion being almost the same in early (<2 weeks) and late (>2 weeks) miscarriages. After TA-CVS, in 28.6 per cent only mycoplasmas, and this only in late miscarriages (> 2 weeks), were involved, accounting for 40 per cent of late miscarriages.