Frans J. Los

Fetal outcome in nuchal translucency with emphasis on normal fetal karyotype.

The aim of this study was to evaluate fetal outcome in fetuses with a nuchal translucency thickness of 3 mm or more, with emphasis on those with a normal karyotype. Between 1991 and 1994, a total of 104 pregnancies with suspected ultrasound abnormalities were referred to our prenatal unit for a fetal anomaly scan before 16 weeks of gestation. Of these 104 pregnancies, 54 were referred because of a nuchal translucency thickness of 3 mm or more. Data on these 54 pregnancies will be presented. Karyotyping was performed in all cases. An abnormal karyotype was found in 26/54 (48 per cent) pregnancies. A normal karyotype was established in the remaining 28 pregnancies. In this subset, five associated structural anomalies were detected at the first anomaly scan (9–15 weeks). Two pregnancies were terminated because of isolated nuchal translucency. In four of the continuing 21 pregnancies, additional structural anomalies were detected only at the second anomaly scan (16–20 weeks). Two of these were terminated because of bilateral renal dysplasia and a combination of exomphalos and ectopia cordis. Finally, 19 pregnancies progressed uneventfully and resulted in spontaneous delivery at a median gestational age of 40 weeks. A statistically significant difference in mean nuchal translucency thickness was found between cases with and without associated structural anomalies. This relationship indicates a more pronounced nuchal translucency thickness to be associated with a higher incidence of additional structural anomalies and, as a result, a poorer fetal outcome.

Amniocentesis or chorionic villus sampling in multiple gestations? Experience with 500 cases

500 women with multiple pregnancies underwent amniocentesis or chorionic villus (CV) sampling at our department between January 1988 and July 1997. The aim of this retrospective study was to evaluate the laboratory aspects and the consequences of discordant results in these pregnancies in relation to the method of sampling. Uncertain results in one or both samples, requiring further investigation were more frequent in CV samples (eight times in 163 paired samples, 5 per cent) than in amniotic fluid (AF) samples (once in 298 paired samples, 0·3 per cent). Sampling one fetus twice (erroneous sampling) was seen only once among 163 pregnancies with two CV samples in our study. Cross contamination due to mixed sampling was discovered in two of seven pregnancies that underwent DNA diagnosis in CV and might be a rather regular occuring phenomenon. In none of the 500 pregnancies mixed sampling caused diagnostic dilemmas. A third sampling problem, maternal cell contamination caused a diagnostic problem once among the AF samples. Selective fetal reduction appeared safer after CV sampling than after amniocentesis. Subsequently, CV sampling instead of amniocentesis has become the method of choice for prenatal diagnosis in multiple pregnancies in our department. Copyright

Prenatal diagnosis of fetal abdominal wall defects: a retrospective analysis of 44 cases.

Forty‐four fetal abdominal wall defects, consisting of 31 omphalocoeles, 11 cases of gastroschisis, and two body stalk anomalies (which are excluded from further analysis), were diagnosed at 12–39 weeks (median 26 weeks) of gestation. In 10/31 (32 per cent) cases of omphalocoele and in 4/11 (36 per cent) cases of gastroschisis, multiple congenital anomalies were diagnosed. A normal amount of amniotic fluid was present in 39 cases; in three cases of omphalocoele an abnormal amount of amniotic fluid (polyhydramnios, n=2; oligohydramnios, n=1) was seen. Prenatally, intrauterine growth retardation (IUGR) was diagnosed in each type of anomaly only once, although the birth weight was below the tenth centile in 23 per cent of omphalocoeles and in 36 per cent of cases of gastroschisis. An abnormal prenatal karyotpye was established in 5/25 (20 per cent) cases of omphalocoele versus none in the gastroschisis group. In 36 cases an expectant obstetric management was followed, and in six cases of omphalocoele the pregnancies were terminated because of severe multiple anomalies (n=3) or an abnormal prenatal karyotype (n=3). The preterm delivery rate (excluding terminations) was 12/25 (48 per cent) in the omphalocoele subgroup versus 8/11 (73 per cent) in the gastroschisis subgroup. The Caesarean section rate was almost identical (19 versus 18 per cent) in both subgroups; the majority (n=5) were performed to protect the abdominal wall defect. The overall survival rate was 39 per cent in the omphalocoele group; in all surviving infants this was the sole congenital anomaly and in each instance there was a normal karyotype. In the gastroschisis group, 8/11 (72 per cent) infants survived, of which two children also displayed unilateral hydronephrosis.

Uniparental disomy with and without confined placental mosaicism: a model for trisomic zygote rescue

In the population of children born after prenatal cytogenetic investigation in chorionic villi at our department from 1992 to 1995 (N=3940), three are known to us with uniparental disomy. One case of maternal heterodisomy 16 was prenatally discovered because of trisomy 16 in direct chorionic villi with subsequently normal amniotic fluid cells. The other two had normal karyotypes in chorionic villi. Maternal heterodisomy 15 was postnatally detected in one of them because of Prader–Willi syndrome. Maternal hetero/isodisomy 16 was accidentally encountered in the other case in the course of prenatal DNA analysis of the tuberous sclerosis complex 2 region at 16p13.3.

Prospective prenatal investigations on potential uniparental disomy in cases of confined placental trisomy

In most reported cases of uniparental disomy (UPD) associated with confined placental mosaicism (CPM), a high level of mosaicism or a full trisomy was found in chorionic villi. At the time that we started our investigations, it was not quite clear whether fetal UPD also existed in the more frequently occurring low levels of mosaicism. During a 4‐year period, a follow‐up amniocentesis was performed in all cases of mosaic or non‐mosaic trisomy detected in chorionic villus (CV) semi‐direct preparations and suspected to be confined to the placenta. We performed fluorescent in situ hybridization (FISH) on uncultured amniotic fluid cells to differentiate between generalized mosaicism and CPM. We found 29 cases of CPM and we determined the incidence of UPD in 23 of these cases. Normal biparental chromosome contributions were found in 22 cases. In one case, we detected a maternal heterodisomy for chromosome 16. UPD appeared to be a rare phenomenon in the cases of CPM (type I and/or type III) that we encountered in 3958 consecutively investigated CV samples, and is not the cause of the pregnancy complications found in seven out of 23 cases with CPM.

Accuracy of abnormal karyotypes after the analysis of both short- and long-term culture of chorionic villi

We report in detail the cytogenetic results of 1838 consecutive chorionic villus samples with the availability of both short‐term culture (STC‐villi) and long‐term culture (LTC‐villi) preparations in 1561 cases (84.9%). A high degree of laboratory success (99.5%) and diagnostic accuracy (99.8%) was observed; in four cases of low mosaicism, all four associated with the final birth of a normal child, a small risk of uncertainty was accepted. The combined analysis of STC‐ and LTC‐villi reduced follow‐up amniocenteses by one‐third in comparison with the analysis of STC‐villi alone. We believe that the desired level of quality and accuracy of prenatal cytogenetics in chorionic villi can only be achieved when both STC‐ and LTC‐villi are available. We conclude that CVS might then be the mode of prenatal diagnosis of first choice in pregnancies with a high (cytogenetic) risk. Copyright

Rapid antibody test for prenatal diagnosis of fragile X syndrome on amniotic fluid cells: a new appraisal.

Fragile X syndrome is caused by mutations in the FMR1 gene and is one of the most frequent forms of inherited mental retardation in males. Postnatal and prenatal diagnosis of fragile X syndrome is feasible by direct DNA analysis. A new approach to prenatal diagnosis of fragile X syndrome in amniotic fluid cells is described, using a rapid and simple antibody test on uncultured amniotic fluid cells. The test requires 1 ml of amniotic fluid and the results of this antibody test are available on the same day as the amniocentesis.

The 10, 11-epoxide-10, 11-diol pathway of carbamazepine in early pregnancy in maternal serum, urine, and amniotic fluid : effect of dose, comedication, and relation to outcome of pregnancy

Epoxide metabolites of carbamazepine (CBZ) have been suggested to play a role in the occurrence of congenital malformations observed in infants exposed to CBZ. We have investigated the 10,11-epoxide-10,11-diol pathway of CBZ in pregnant epileptic patients receiving CBZ alone or in combination with other antiepileptic drugs in relation to the outcome of pregnancy in a prospective manner. The women were referred to our clinic before 16 weeks of gestation for prenatal diagnosis of fetal malformations, including neural tube defects, by ultrasound and amniocentesis. The availability of amniotic fluid samples enabled us to determine to what extent CBZ and its main metabolites reached the amniotic fluid. In 100 pregnancies with first trimester CBZ exposure (including 7 with malformed outcome), parent drug and metabolite concentrations in maternal serum were evaluated. CBZ-10,11-epoxide concentrations increased with increasing dose. Comedication with phenobarbital led to lower 10,11-epoxide concentrations in maternal serum and a higher percentage of the dose recovered in urine as 10,11-diol. Valproate comedication led to slightly higher 10,11-epoxide concentrations in maternal serum, in combination with lower CBZ concentrations and a lower percentage of the dose recovered in the urine as 10,11-diol, in amniotic fluid, concentrations of CBZ and its main metabolites in most patients were 2 to 2.5 times higher than the free concentrations in maternal serum. Metabolites and parent drug concentrations in amniotic fluid correlated with their free concentration in maternal serum, but stronger with each other in amniotic fluid. No significant differences in levels of CBZ and its metabolites were observed between pregnancies with normal and malformed outcome.

Prenatal diagnosis of trisomy 9: cytogenetic, FISH, and DNA studies

A cytogenetic survey and follow‐up studies were performed in eight cases of full, mosaic, and pseudomosaic trisomy 9 prenatally diagnosed among 36 213 prenatal samples in our department between August 1970 and July 1996. Besides conventional chromosome analysis, interphase fluorescent in situ hybridization (FISH) was employed. FISH turned out to be a rapid and accurate method for verification of trisomy cell lines and could provide additional information to the prenatal cytogenetic results. FISH also enables the study of uncultured specimens of amniotic fluid, not accessible for traditional cytogenetic analysis. In three cases, retrospective DNA analysis showed the supernumerary chromosome 9 to be of maternal origin. The disomic cell lines in both mosaic trisomy 9 cases showed maternal uniparental disomy.

A case of early intrauterine parvovirus B19 infection

We present a case of parvovirus B19 infection in the first trimester, confirmed by polymerase chain reaction (PCR) in amniotic fluid and cord blood, that caused myocarditis, severe intrauterine growth retardation, and probably glomerulonephritis. Eventually a small‐for‐dates neonate was born, without any signs of the infection.