Optimising the timing for nuchal translucency measurement

It appears from current evidence that the most effective screening strategy for Down syndrome will involve a combination of first trimester nuchal translucency and serum biochemistry, whether performed in the first or second trimester. The aim of this study was to determine the optimum gestation based upon menstrual dates at which to schedule nuchal translucency (NT) measurement for the evaluation of fetal Down syndrome risk. Five thousand eight hundred and thirty-five pregnancies had an ultrasound scan scheduled between 11 and 14 completed weeks of gestation based upon either the last menstrual period (n = 3199) or a prior ultrasound scan (n = 2636). For last menstrual period-based ultrasound scans, with advancing gestation the frequency of missed miscarriage significantly decreased (p = 0.009, chi squared test), as did the need to reschedule a further scan because the gestation of the scheduled scan was too early to measure NT (p < 0.0001, Chi-squared test). In contrast, with advancing gestation the rate of unsuccessful NT measurement because the crown–rump length (CRL) was greater than 84 mm significantly increased (p < 0.0001, Chi-squared test). Of the women who had had an earlier ultrasound, 42 (1.6%) had a missed miscarriage and 9 (0.3%) were over gestation at the time of the NT scan. These data suggest that when only the last menstrual period is known the optimum time to schedule a nuchal translucency measurement is at 12 to 13 weeks' gestation. Copyright © 2002 John Wiley & Sons, Ltd.     

The pattern of metal deposition to a woodland ecosystem as revealed by bryophyte analysis

The concentrations and enrichment factor data for 7 metals has been investigated in samples of Hypnum cupressiforme obtained from various parts of a woodland located to the south east of London and immediately adjacent to the M 25 motorway. Despite the rural location of the woodland, metal level and enrichment factor data suggest a moderate degree of contamination. Application of analysis of variance to the data indicates individual metal levels at woodland edges are significantly different from adjacent internal sites, suggesting enhanced deposition at these edges. The fact that this significance pattern is not repeated at all edges indicates a directional influence on levels. Correlation coefficient data indicates metal/metal associations and allows some speculation about the major pathways by which metals are atmospherically transported to and deposited in the woodland.