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Objective: Many studies have shown that an increased nuchal translucency (NT) may be a good marker of fetal heart malformation, but the extent to which NT is suitable for identifying the population at risk remains unclear. We aimed to determine the value of NT measurement and of the presence of cystic hygroma colli in the screening of euploid fetuses for congenital heart defects (CHD). Methods: We carried out a retrospective analysis of 12 910 euploid pregnancies examined between January 1995 and August 2007 at our institution. The screening performance of NT measurements in identifying fetuses with CHD was assessed, with comparison between the use of cut-offs defined as absolute values, multiples of the median (MoM) and percentiles. The presence of cystic hygroma colli was also assessed in the prediction of CHD. Results: The incidence of major CHD was 3.4 per thousand (44/12 910). The sensitivity of NT measurement in screening for major CHD was 54.5% if the threshold was set at the 95(th) percentile, 45.4% if it was set at 3 mm, 27.3% for 3.5 mm, 50.0% for 1.5 MoM and 45.5% for 1.75 MoM. The false-positive rates for these thresholds were 8.4, 6.6, 1.7, 8.9 and 6.3%, respectively. The incidence of major CHD was 1.2% (10/813) in cases of thick NT (> 95(th) centile) and 4.3% (13/304) in cases of hygroma colli. Conclusions: NT measurement during the first trimester is potentially useful for screening for fetal major CHD. Screening performance is consistent whether NT values are expressed as MoMs, percentiles or absolute values. The incidence of major CHD seems to be higher in cases of cystic hygroma colli. [ABSTRACT FROM AUTHOR]

At the western border of its geographical range, Silene nutans (Caryophyllaceae) has evolved two groups of parapatric populations showingdistinct allozyme patterns and apparently occurring on different bedrock types. This study tests the hypothesis that these groups represent edaphic ecotypes. With this in view, the ecological amplitude of 36 populations of Silene nutans from Belgium was investigated and their synecology specified using vegetation composition and soil parameters; Ellenberg indicator values were used for ecological interpretation of the vegetation analyses. The results provide evidence that allozyme and habitat variations are correlated, the two groups occurring on contrasting soil with distinct vegetation types. One group is restricted to alkaline soils and typically occurs in open calcareous grasslands, fringes and scrub. The other group is characterized by wider autecological and synecological ranges with a bimodal pH-distribution,occurring on two kinds of siliceous soils: (1) neutral soils, supporting vegetation with a high species richness comprising many mesophilous species, and (2) CaCO3-free bedrocks characterized by acidophilous, species-poor, open dry grasslands and woodlands. It also appears that factors not related to soil chemistry, such as microclimate, are involved in the ecological specialization of the two ecotypes. It is argued that these ecotypes. exemplify adaptive radiation and parapatric speciation at the margin of a species distribution area. [ABSTRACT FROM AUTHOR]