Assessment and management of fetal agenesis of the corpus callosum

Prenatal counselling for fetal agenesis of the corpus callosum is difficult as the prognosis until now has been so uncertain. We have reviewed the current world English literature to provide the best probabilistic information for prospective parents. In total, there are 70 cases where the diagnosis was made prenatally. The diagnosis of apparently isolated agenesis of the corpus callosum (in the absence of other sonographically detectable anomalies) appears to carry an excellent prognosis, with an 85 per cent chance of a normal developmental outcome and a 15 per cent risk of handicap. Fetal karyotyping is recommended as there is a 1 in 10 risk of aneuploidy. If other anomalies are detected prenatally, the outcome is very poor. Termination of pregnancy is advised in these circumstances.     

A survey of diagnostic amniocenteses in Oxford from 1974–1981

A survey was conducted of the results of mid-trimester diagnostic amniocenteses in the Oxford Region from 1974 to 1981. The survey used data relating to all 4357 singleton pregnancies in which an amniocentesis was performed during this period. Follow-up information on outcome was obtained in respect of 4284 (98 per cent) pregnancies. A cell culture to determine karyotype and an alpha-fetoprotein determination was carried out in all cases. From 1974 to 1981 amniocenteses became increasingly common, rising from 2 to 32 per 1000 births. The most common indication for amniocentesis was a high risk of a chromosome abnormality–56 per cent of all amniocenteses. Within this group advanced maternal age was responsible for 89 per cent of the cases. The next most common indication was a high risk of a neural tube defect (37 per cent of all amniocenteses)–in 1974 a raised maternal serum alpha-fetoprotein level accounted for only 4 per cent of these; by 1981 this had risen to 67 per cent. There were seven false-positive and 132 true-positive diagnoses of neural tube defect; since 1981, with the introduction of amniotic fluid acetylocholinesterase determination as a secondary diagnostic test for neural tube defects, there have been no further false-positive diagnoses. In 1981 76 per cent of women aged 35 years or more did not have an amniocentesis. It is not known to what extent this was due to not offering women in this age group amniocentesis or to women not accepting such an offer.     

航天器在轨自主热故障诊断专家系统研究

航天器在轨自主进行热故障诊断对其顺利完成任务具有非常重要的意义。文中所提出的专家系统推理机制采取基于事例和基于规则相结合的方法构造;而知识获取广泛吸取历史经验和专家知识,采用产生式规则进行知识表示。最后利用VB完成了该专家系统,通过验证,发现它具有很好的实用性。     

区域PERE系统的通用自组织演化模型

分析了区域人口－经济－资源－环境系统的自组织过程，建立了区域ＰＥＲＥ系统的通用自组织演化模型，并把模型应用于山西省某市，预测了市未来的人口、经济和环境状况试图解决在区域ＰＥＲＥ系统中应用自组织理论时建模困难的问题。     

Genetic amniocentesis in biamniotic twin pregnancies by a single transabdominal insertion of the needle

We present a technique to aspirate amniotic fluid from both sacs in biamniotic twin pregnancies using a single abdominal insertion with a spinal needle. It was successful in 48 out of 55 cases of biamniotic twin pregnancies referred to our perinatal unit between 1985 and 1994. The single insertion technique was used when the inter-amniotic membrane was clearly evident and two separate free amniotic fluid pools could be reached by the operator with a single puncture. An adequate amount of amniotic fluid was sampled from both sacs to make a cytogenetic diagnosis in all cases. There were four fetuses with trisomy 21 in three twin pregnancies. In two cases, only one twin was affected whilst the co-twin was normal, so that a selective feticide was performed. No miscarriages due to genetic amniocentesis were reported. After 1990, all genetic amniocenteses in biamniotic twin pregnancies (except for one case due to late booking) were performed between 14 and 15 weeks of gestation and with all cases except one, it was possible to sample both twins by a single puncture. We suggest that early amniocentesis (14–15 weeks) by a single abdominal puncture could be a reliable and safe alternative to first-trimester chorionic villus sampling in twin pregnancies.     

Transabdominal chorionic villus sampling in the second and third trimesters of pregnancy: Chromosome quality,reporting time,and feto-maternal bleeding

Transabdominal chorionic villus sampling (TA-CVS) was performed in 210 pregnancies from 13 to 38 weeks using a double-needle technique. The sampling success was comparable to first-trimester TA-CVS and the diagnostic success rate was 98.2 per cent for the short-term technique and 99.3 per cent for cultured villi. Two fetuses could not be karyotyped. We found the chromosome quality to be similar to that in the first trimester, comparing the number of G-bands and other chromosome attributes. There were no unintended losses in a group (n = 142) with no sonographic abnormality, except for one death in utero at 38 weeks, 20 weeks after sampling. Chromosomal aberrations were seen in 19 per cent of cases with abnormal sonograms (n = 58). One case of a discordant karyotype was found (false-negative prediction of Down's syndrome by the short-term preparation). There were no cases of fetal demise due to feto-maternal bleeding. It is suggested that double-needle TA-CVS in advanced pregnancies combines the advantages of rapid karyotyping of chromosomes of good quality and low risk for the fetus, and seems to be easier to practise and is probably safer than cordocentesis.     

Prenatal ultrasound diagnosis of Apert's syndrome

A mother affected with Apert's syndrome was diagnosed by ultrasound scan at 16–17 weeks to have a fetus similarly affected. The typical features of acrocephaly and symmetrical syndactyly were seen. This is probably the first time that this condition has been diagnosed at such a gestation by ultrasound scan. The patient decided to continue the pregnancy, and intrauterine death occurred at 34 weeks. The diagnosis was confirmed by pathological examination.     

Selective survival of only the healthy fetus following prenatal diagnosis of thalassaemia major in binovular twin gestation

Selective feticide is the procedure of choice when, in twin binovular pregnancy, only one of the fetuses is shown to be affected. As the probabilities for this condition are almost 1:2 when the genetic disease is due to homozygosity for two autosomal recessive genes, the problem is expected to occur frequently among the ever increasing number of couples seeking prenatal diagnosis of thalassaemia and the haemoglobinopathies. The present report is the first case of this condition and the ninth in the overall medical literature.     

Ultrasonography in pregnancy and fetal abnormalities: Screening or diagnostic test? IPIMC 1986–1990 register data

The aim of the present study was to assess the sensitivity of ultrasound diagnosis used as a screening test in detecting major congenital anomalies in the prenatal period in a large nation-based multicentre setting. Data from the IPIMC register were collected in the period 1986–1990. One hundred and thirty-five hospitals, located in 17 out of the 20 regions in Italy, participated in the register. Study cases were 3479 infants with major congenital anomalies diagnosed at birth or in the first week of life. Subjects with chromosomal anomalies or multiple defects were excluded. The sensitivity of ultrasound prenatal diagnosis was 49.5 per cent for central nervous system anomalies, 3.8 per cent for congenital heart diseases, 17.1 per cent for gastrointestinal tract defects, 46.6 per cent for abdominal wall defects, 74.8 per cent for urinary tract anomalies, and 22.9 per cent for skeletal abnormalities. The detection rate for diaphragmatic hernia was 24.2 per cent. Overall, only 18 per cent of the defects diagnosed in utero were detected before 24 weeks' gestation. The sensitivity of prenatal diagnosis was 30.1 and 19.0 per cent in the northern, central, and southern regions, respectively. In light of its low sensitivity, ultrasonography as a screening test in the general population should be abandoned, although some improvement in its performance should be expected following adequate training of the ultrasound staff and the use of good technical equipment.     

First-trimester prenatal diagnosis in quintuplets: A practical approach using step-by-step embryo reduction

A multiple pregnancy of high rank may occur in a couple at risk for a Mendelian disorder. Prenatal diagnosis is hampered by the difficulty of (1) obtaining chorionic villi from each zygote arid (2) unequivocally relating each sample to the corresponding embryo. The calculation of the genetic risk according to the number of zygotes led us to propose a diagnostic strategy based on embryo reduction, a technique initially designed to improve the perinatal outcome of multiple pregnancies with normal embryos. We report a case in which this approach allowed rational use of first-trimester chorionic villus sampling in a quintuplet pregnancy at risk for non-ketotic hyperglycinaemia, resulting in the selective birth of unaffected twins.