氢化物原子荧光法同时测定水中的硒和汞

采用氢化物一原子荧光法，应用AFS-2202a型双道原子荧光仪联合测定水中的硒和汞，方法的检出限为：Se0．31μg／L、Hg0．01μg／L，线性范围为：Se0-20．0μg／L、Hg0～2．00μg／L。     

Does a ‘notched’ nuchal translucency indicate Down syndrome fetuses or other adverse pregnancy outcome?

The aim of the present study was to assess the sonographic contour of the increased nuchal translucency (NT) and to correlate this with pregnancy outcome. Fifty sonographic images of fetuses with increased NT [>95th centile thickness of the normal range for crown–rump length (CRL) between 38 and 84 mm] were retrospectively assessed. In all the cases a complete pregnancy and even infancy follow-up (<36 months) was available. The NT appearances were subdivided into two forms: a ‘notched’ or ‘uniform’ appearance. The images were correlated with karyotype results [trisomy 21 (DS) vs euploid cases] and pregnancy outcome. Complicated outcomes were classified as being either DS fetuses, miscarriage or termination of pregnancy because of structural anomaly. Thus 30/35 (86%) of the euploid fetuses had a ‘uniformly’ increased NT, whereas 8/13 DS cases (62%) had a ‘notched’ appearance (Fisher's exact test, p=0.004). Additionally, 27/29 fetuses (93%) which had an uneventful pregnancy outcome had a ‘uniform’ increased NT, whereas 12/26 (57%) of the fetuses which had adverse pregnancy outcome had a ‘notched’ appearance of their NT (Fisher's exact test, p<0.001). Although it was not possible to correlate the sonographic data with post-evacuation microdissection findings, it is possible that a uniformly shaped, increased NT may be more representative of a developmental delay in a normal fetus. Conversely, a ‘notched’ nuchal surface may represent abnormal lymphatic or cardiovascular development more commonly seen in DS fetuses. Copyright © 2001 John Wiley & Sons, Ltd.     

The effect of fetal gender on second-trimester maternal serum inhibin-A concentration

Second-trimester serum inhibin-A is increasingly used as a fourth marker in addition to the triple test to screen for Down syndrome. We investigated whether fetal gender had an effect on serum inhibin-A concentration. A retrospective analysis was done on 316 normal pregnancies and 48 Down syndrome pregnancies in which maternal serum inhibin-A assays were performed between 15 and 20 weeks of gestation and in which the fetal sex was known. The median inhibin-A MoM (95% CI) for normal pregnancies in the presence of a male fetus was 0.93 (range 0.88–1.03). This was significantly lower than that in the presence of a female fetus (median MoM=1.04). The gender difference was not observed in the Down syndrome pregnancies. The increased inhibin-A concentration would lead to a 2.3-fold higher false-positive rate in the presence of a female fetus (10.6% vs 4.6%; p<0.05, Chi-square test). Because of the small number of cases studied, the results need to be substantiated by a larger series. If the gender effect is confirmed, adjustment for fetal sex may be necessary when inhibin-A is used as a screening marker. Copyright © 2001 John Wiley & Sons, Ltd.     

Prenatal diagnosis of sex chromosome aneuploidy: possible reasons for high rates of pregnancy termination

Sex chromosome aneuploidy (SCA), when detected in amniocentesis, is usually an unexpected result of a test carried out for another purpose. For most SCAs, the prognosis is milder and less predictable than trisomy 21, and therefore parents are faced with a difficult decision regarding the option of pregnancy termination. While studies from Europe and the USA report a declining trend in termination rates for SCA, our local experience is different. During the period 1989–1998, we diagnosed 60 SCA (including mosaics) in 20 106 amniocenteses (0.29%) and 48 (80%) of these pregnancies were terminated, a significantly higher proportion than has been reported in Europe and the USA. The present study shows that the difference between our experience and others' may be related to differences in cultural norms and values. Thirty women were interviewed, of whom 23 terminated and seven continued the pregnancy. Interview analyses showed that the main reason behind the decision to terminate the pregnancy was associated with the parents' fear of non-specific abnormality of the child, and concerns about abnormal sexual development. Although genetic counseling practised in our center aims to be non-directive, 56% of the women reported that the counseling was either directive towards termination, or that they at least felt that the counselor's attitude was pro-termination. Most women (93%) reported themselves as having come to terms with their decision. Copyright © 2001 John Wiley & Sons, Ltd.