In a retrospective collaborative study involving 21 U.K. laboratories and 11,775 CVS prenatal diagnostic procedures, a total of 73 cases of confined placental mosaicism (CPM) were identified among the 8004 first-trimester referrals because of advanced maternal age, a previous child with a numerical chromosome abnormality, or a family history of the same. Data were collected on subsequent cytogenetic follow-up and pregnancy outcome for each case and a referral matched control. Comparison with the control population failed to demonstrate a marked increase in adverse pregnancy outcome in the CPM group, but a significant increase in both low and high birth weight infants was recorded. In a parallel study, 7 out of 108 cases, referred for prenatal diagnosis because of ultrasound detection of isolated intrauterine growth retardation (IUGR) in the second or third trimester, were shown to have a chromosome abnormality restricted to the extraembryonic tissues. These included cases of CPM involving trisomy 9 and del(13)(q13), neither of which has previously been reported in association with IUGR.
We investigated the use of amniocentesis performed at eight to 14 weeks' gestation as a possible alternative to chorionic villus sampling. Patients, methods, and results Samples of amniotic fluid were taken from 40 gestation, and the mean time to the cells being harvested was 12 6 days. In contrast only 17 (68%) of the 25 samples taken at eight to 11 weeks yielded a result. One sample taken at 13 weeks' gestation yielded a female karyotype, whereas the fetal parts revealed a male karyotype; the sample was subsequently identified as maternal urine. The mean volume of amniotic fluid obtained was 13 9 ml (range 1-40 ml). CommentAll 15 samples taken at 12-14 weeks' gestation yielded a result. The mean time to cells being harvested in this group (12-6 days) compared favourably with the current mean of 11 days for the samples obtained routinely at [16][17][18][19] weeks that are processed by our laboratory. Culture of all the 5 ml aliquots obtained at 12-14 weeks was successful. Thus a 10 ml sample would provide two cultures, which are necessary for the interpretation of equivocal results and in case of microbial infection.In one case, a urine sample was obtained at 13 weeks' gestation from an obese patient in whom imaging was poor. In a clinical environment sampling would not have been attempted, and this patient would have been recalled later.Our results show that amniocentesis from as early as 12 weeks' gestation can provide sufficient material for cytogenetic diagnosis and could be offered as an alternative to current methods of prenatal diagnosis. Furthermore, the procedure could be carried out by doctors already familiar with the technique, using existing resources. Patients must, however, be advised that the risks of this procedure are unknown. Preliminary reports from the United States suggest that early amniocentesis is safer than chorionic villus sampling.24 Further evaluation, preferably by means of a randomised trial, is urgently needed. We are continuing our investigation of amniocentesis before 12 weeks with the aim of bringing the procedure forward into the first trimester of pregnancy.We acknowledge contributions to the study from Mr N Fisk, Mr P Reginald, Mr M Michel, and Mrs R Rebello.
We describe a girl with physical anomalies, accelerated skeletal maturation, failure to thrive, and respiratory difficulties consistent with a diagnosis of Marshall-Smith syndrome (MSS). Chromosome analysis showed an inverted duplication of chromosome 2 [46,XX,inv dup(2)(q37q32) de novo] identified by G banding and confirmed by FISH. Several cases of trisomy 2q3 have been reported and established a syndrome, but the present case is the first to be associated with accelerated skeletal maturation and a clinical picture resembling MSS. This raises the possibility that the cause of MSS involves the q3 region of chromosome 2. Few reports of MSS include study of the karyotype, although the chromosomes were apparently normal in those cases where they have been examined. We suggest that karyotyping be undertaken with particular attention to the 2q3 region in patients with suspected MSS. It also would be prudent to assess bone age in all children with trisomy 2q.
Early amniocentesis between 11 and 14 weeks' gestation was offered to 110 women at risk of a chromosomally abnormal fetus due to maternal age. Four were found to be unsuitable for the procedure, and 106 early amniocenteses were performed. In 102 cases, clear amniotic fluid was obtained with a single tap. There were two dry taps and two bloodstained taps; sampling was repeated in three of these cases before 15 weeks. In the fourth case, placental biopsy was performed at 16 weeks. Thus, we were able to obtain a satisfactory sample in all but three cases (2.8 per cent). Karyotyping of cells harvested from the early amniotic fluid samples was successful in all the 105 cases. Cell culture from the initial samples revealed a normal karyotype in 99 cases, two balanced translocations, two tetraploid karyotypes, and two cases of pseudomosaicism. Of the 105 pregnancies successfully sampled, there have been two losses to date (1.8 per cent). Two further patients presented with premature rupture of membranes, both pregnancies having successful outcomes. Sixty-two babies have delivered to date, with four congenital anomalies. There were no respiratory problems. Twenty-nine pregnancies are continuing without known complications, and details are not yet available on the remaining 12. The results indicate that early amniocentesis may replace the traditional test at 15-17 weeks.
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