Department of ultrasound, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, 100730, China.
BMC Pregnancy Childbirth. 2021 May 8;21(1):365. doi: 10.1186/s12884-021-03830-5.
Accurate estimation of fetal weight is important for prenatal care and for detection of fetal growth abnormalities. Prediction of fetal weight entails the indirect measurement of fetal biometry by ultrasound that is then introduced into formulae to calculate the estimated fetal weight. The aim of our study was to evaluate the accuracy of fetal weight estimation of Chinese fetuses in the third trimester using an automated three-dimensional (3D) fractional limb volume model, and to compare this model with the traditional two-dimensional (2D) model.
Prospective 2D and 3D ultrasonography were performed among women with singleton pregnancies 7 days before delivery to obtain 2D data, including fetal biparietal diameter, abdominal circumference and femur length, as well as 3D data, including the fractional arm volume (AVol) and fractional thigh volume (TVol). The fetal weight was estimated using the 2D model and the 3D fractional limb volume model respectively. Percentage error was defined as (estimated fetal weight - actual birth weight) divided by actual birth weight and multiplied by 100. Systematic errors (accuracy) were evaluated as the mean percentage error (MPE). Random errors (precision) were calculated as ±1 SD of percentage error. The intraclass correlation coefficient (ICC) was used to analyze the inter-observer reliability of the 3D ultrasound measurements of fractional limb volume.
Ultrasound examination was performed on 56 fetuses at 39.6 ± 1.4 weeks' gestation. The average birth weight of the newborns was 3393 ± 530 g. The average fetal weight estimated by the 2D model was 3478 ± 467 g, and the MPE was 3.2 ± 8.9. The average fetal weights estimated by AVol and TVol of the 3D model were 3268 ± 467 g and 3250 ± 485 g, respectively, and the MPEs were - 3.3 ± 6.6 and - 3.9 ± 6.1, respectively. For the 3D TVol model, the proportion of fetuses with estimated error ≤ 5% was significantly higher than that of the 2D model (55.4% vs. 33.9%, p < 0.05). For fetuses with a birth weight < 3500 g, the accuracy of the AVol and TVol models were better than the 2D model (- 0.8 vs. 7.0 and - 2.8 vs. 7.0, both p < 0.05). Moreover, for these fetuses, the proportions of estimated error ≤ 5% of the AVol and TVol models were 58.1 and 64.5%, respectively, significantly higher than that of the 2D model (19.4%) (both p < 0.05). The inter-observer reliability of measuring fetal AVol and TVol were high, with the ICCs of 0.921 and 0.963, respectively.
In this cohort, the automated 3D fractional limb volume model improves the accuracy of weight estimation in most third-trimester fetuses. Prediction accuracy of the 3D model for neonatal BW, particularly < 3500 g was higher than that of the traditional 2D model.
准确估计胎儿体重对于产前保健和发现胎儿生长异常非常重要。预测胎儿体重需要通过超声间接测量胎儿生物测量值，然后将其引入公式计算估计的胎儿体重。我们的研究目的是评估使用自动化三维（3D）肢体分数体积模型对中国胎儿在妊娠晚期体重估计的准确性，并将该模型与传统二维（2D）模型进行比较。
前瞻性对 7 天内分娩的单胎妊娠孕妇进行二维和三维超声检查，以获得二维数据，包括胎儿双顶间径、腹围和股骨长度，以及三维数据，包括肢体分数体积（AVol）和肢体分数体积（TVol）。分别使用二维模型和 3D 肢体分数体积模型估计胎儿体重。百分比误差定义为（估计胎儿体重-实际出生体重）除以实际出生体重再乘以 100。系统误差（准确性）用平均百分比误差（MPE）评估。随机误差（精密度）用百分比误差的±1 SD 计算。使用组内相关系数（ICC）分析 3D 超声测量肢体分数体积的观察者间可靠性。
对 39.6±1.4 周妊娠的 56 例胎儿进行了超声检查。新生儿的平均出生体重为 3393±530g。二维模型估计的胎儿平均体重为 3478±467g，MPE 为 3.2±8.9。3D 模型的 AVol 和 TVol 分别估计胎儿体重为 3268±467g 和 3250±485g，MPE 分别为-3.3±6.6 和-3.9±6.1。对于 3D TVol 模型，估计误差≤5%的胎儿比例明显高于二维模型（55.4% vs. 33.9%，p<0.05）。对于出生体重<3500g 的胎儿，AVol 和 TVol 模型的准确性优于二维模型（-0.8 vs. 7.0 和-2.8 vs. 7.0，均 p<0.05）。此外，这些胎儿的 AVol 和 TVol 模型估计误差≤5%的比例分别为 58.1%和 64.5%，明显高于二维模型（19.4%）（均 p<0.05）。测量胎儿 AVol 和 TVol 的观察者间可靠性较高，ICC 分别为 0.921 和 0.963。
在本队列中，自动化 3D 肢体分数体积模型提高了大多数妊娠晚期胎儿体重估计的准确性。3D 模型对新生儿 BW 的预测准确性，特别是<3500g 的预测准确性高于传统 2D 模型。
