Watt H C, Wald N J
Department of Environmental and Preventive Medicine, Wolfson Institute of Preventive Medicine, St Bartholonew's, U.K.
Prenat Diagn. 1998 Aug;18(8):842-5.
Serum markers used in screening for Down syndrome and neural tube defects are often adjusted to take account of the effect of maternal weight on the marker levels. The standard adjustment procedure is based on a linear relationship between the marker concentration, expressed as the log of the multiple of the median (MOM), and maternal weight on a linear scale. It has been proposed that maternal weight adjustment may be better performed using a linear relationship between marker concentration expressed in MOM and the reciprocal of maternal weight. In a dataset of 8905 singleton pregnancies in white women without Down syndrome or neural tube defects we compared the two methods of weight adjustment and found that both were satisfactory and neither had an obvious advantage over the other. In the analysis it was noticed that hCG levels in very heavy women (> 120 kg) were higher than expected from the decreasing linear trend with maternal weight--a result that was statistically highly significant (p < 0.01) but for which we have no explanation. In screening it will have virtually no effect because the finding was restricted to only the 0.3 per cent of the heaviest women.
用于唐氏综合征和神经管缺陷筛查的血清标志物通常会进行调整，以考虑孕妇体重对标志物水平的影响。标准的调整程序基于标志物浓度（以中位数倍数的对数表示，即MOM）与线性尺度上的孕妇体重之间的线性关系。有人提出，使用MOM表示的标志物浓度与孕妇体重的倒数之间的线性关系可能会更好地进行孕妇体重调整。在一个包含8905例无唐氏综合征或神经管缺陷的白人单胎妊娠的数据集里，我们比较了两种体重调整方法，发现两种方法都令人满意，且没有一种方法比另一种方法有明显优势。在分析过程中注意到，体重非常重（>120kg）的女性的hCG水平高于根据与孕妇体重的下降线性趋势预期的水平——这一结果在统计学上具有高度显著性（p<0.01），但我们对此无法解释。在筛查中，这实际上不会产生影响，因为该发现仅局限于体重最重的0.3%的女性。
