Institute of Community Medicine, University of Tromsø, Tromsø, Norway.
J Bone Miner Res. 2010 May;25(5):1029-33. doi: 10.1359/jbmr.091107.
Bone size is a determinant of bone strength and tracks in its percentile of origin during childhood and adolescence. We hypothesized that the ranking of an individual's femur length (FL) is established in early gestation and tracks thereafter. Fetal FL was measured serially using 2D ultrasound in 625 Norwegian fetuses. Tracking was assessed using Pearson correlation, a generalized estimating equation model, and by calculating the proportion of fetuses whose FL remained within the same quartile. Baseline FL Z-score (weeks 10 to 19) and later measurements correlated, but more weakly as gestation advanced: r = 0.59 (weeks 20 to 26); r = 0.45 (weeks 27 to 33); and r = 0.32 (weeks 34 to 39) (p < 0.001). Tracking within the same quartile throughout gestation occurred in 13% of fetuses. Of the 87% deviating, 21% returned to the quartile of origin, so 34% began and ended in the same quartile, 38% deviated by one quartile, and 28% deviated by two or more quartiles by the end of gestation. A standard deviation higher baseline FL Z-score, placental weight (150 g), maternal height (5 cm), and weight (10 kg), was associated with a 0.25, 0.15, 0.10, and 0.05 SD higher FL Z-score at the end of gestation, respectively (p ranging from <0.001 to 0.02). Tracking within the same percentile throughout the whole of gestation, as suggest by growth charts, is uncommon. Deviation from tracking is more common and is the result of changes in growth velocity within and between fetuses and is partly influenced by maternal, fetal, and placental factors.
骨量是骨强度的决定因素，在儿童和青少年时期，其起源的百分位数与其相关。我们假设个体股骨长度（FL）的排名在早期妊娠时就已确定，并在此后一直跟踪。在 625 名挪威胎儿中，我们使用二维超声连续测量胎儿 FL。使用 Pearson 相关系数、广义估计方程模型和计算 FL 仍处于同一四分位数的胎儿比例来评估跟踪情况。基线 FL Z 分数（10 至 19 周）与后期测量相关，但随着妊娠的进展相关性减弱：r = 0.59（20 至 26 周）；r = 0.45（27 至 33 周）；r = 0.32（34 至 39 周）（p < 0.001）。在整个妊娠期间，13%的胎儿在同一四分位数内跟踪。在 87%偏离的胎儿中，21%返回原始四分位数，因此 34%的胎儿从开始到结束都在同一四分位数内，38%偏离一个四分位数，28%在妊娠结束时偏离两个或更多四分位数。基线 FL Z 分数较高（标准差为 0.25）、胎盘重量（150 克）、母亲身高（5 厘米）和体重（10 公斤）较高，与妊娠结束时 FL Z 分数较高（分别为 0.15、0.10 和 0.05 标准差）相关（p 范围从<0.001 到 0.02）。正如生长图表所表明的那样，整个妊娠期间都在同一百分位数内跟踪是不常见的。偏离跟踪更为常见，这是由于胎儿内和胎儿之间生长速度的变化所致，部分受到母亲、胎儿和胎盘因素的影响。
