National Center for Fetal Medicine, Women and Children's Center, St Olavs University Hospital, Trondheim, Norway.
Ultrasound Obstet Gynecol. 2010 Dec;36(6):728-34. doi: 10.1002/uog.7707. Epub 2010 Jun 8.
To evaluate two Norwegian traditional, sample-based term prediction models as applied to the data from a large population-based registry. The two models were also compared with an established German model.
Our database included information from 41 343 non-selected ultrasound scans registered over the years 1987-2005. The prediction models were applied to measurements from the ultrasound examinations, and the resulting term predictions were compared with the actual times of the deliveries. The median bias (the difference between the true and the predicted date of delivery) was calculated for each model, both for the study population as a whole and for subgroups of measurements of biparietal diameter (BPD) and femur length (FL). Secondary measures, i.e. proportion of births within ± 14 days and the rates of preterm and post-term deliveries, were also assessed.
The analyses showed that the models had significant biases, predicting delivery date either too late or too early. For each model the size of the bias varied, depending on the fetal size at the time of the examination; the extremes were minus 4 and plus 4 days for the BPD-based predictions. There were similar results with the FL-based predictions.
Term predictions made with traditional sample-based models had significant biases that varied over each method's measurement range. These models have important shortcomings, probably because of strict selection criteria in the process of constructing the models, and because the methods primarily aim at estimating the last menstrual period-based day of conception, not the day of birth.
评估两种挪威传统的基于样本的预测模型在大规模基于人群的登记处数据中的应用。还将这两种模型与一种已建立的德国模型进行了比较。
我们的数据库包含了 1987 年至 2005 年间非选择性超声扫描的信息，共 41343 例。将预测模型应用于超声检查的测量值，并将得到的足月预测值与实际分娩时间进行比较。计算了每个模型的中位数偏差（实际分娩日期与预测分娩日期的差异），包括整个研究人群以及双顶径（BPD）和股骨长度（FL）测量值的亚组。还评估了次要指标，即出生在±14 天内的比例以及早产和过期分娩的发生率。
分析表明，这些模型存在显著的偏差，预测分娩日期要么过早，要么过晚。对于每个模型，偏差的大小取决于检查时胎儿的大小；BPD 预测的偏差范围为 4 天以内和 4 天以外。基于 FL 的预测也有类似的结果。
使用传统的基于样本的预测模型进行的足月预测存在显著偏差，这些偏差随着每个模型的测量范围而变化。这些模型存在重要的缺点，可能是因为在构建模型的过程中存在严格的选择标准，并且因为这些方法主要旨在估计末次月经周期的受孕日，而不是出生日期。
