Shanghai First Maternity and Infant Health Hospital, Tongji University School of Medicine, Shanghai, China.
Arch Gynecol Obstet. 2011 Sep;284(3):599-606. doi: 10.1007/s00404-010-1730-8. Epub 2010 Nov 3.
Compared with normal birth weight fetuses (2,500-4,000 g), accurate fetal weight estimation for fetuses with low or excessive weight is considered more important for fetal compromise prediction and labor management. New formulas were developed to estimate weight for low birth weight (LBW) fetuses and macrosomic fetuses, respectively.
A total of 523 fetuses with birth weight less than 2,500 g, 652 fetuses with normal birth weight, and 239 fetuses with birth weight more than 4,000 g were included in the study. As much as 25 existing formulas which incorporate regularly defined fetal measurements were evaluated and compared. Performance evaluation of existing formulas showed that no formulas can provide consistently accurate weight estimation both for LBW fetuses and macrosomic fetuses. A total of 1,034 cases were utilized to generate an overall regression formula. If the pre-estimated weight fell into the suspicious LBW and macrosomia range, the value was then updated by using the new regression formulas for LBW fetuses and macrosomic fetuses. As the training group, 262 LBW fetuses and 120 macrosomic fetuses were employed in a stepwise linear regression to obtain two update regression formulas for suspicious LBW fetuses and macrosomic fetuses. As the validation group, another 261 LBW fetuses and 119 macrosomic fetuses were assessed.
The new overall formula has the form of Log(10)BW = 0.180(HC) + 0.00628(AC) - 0.00318(HC)(2) + 0.00173(AC)(FL) + 0.0000430(BPD)(HC)(2). The update formula for suspicious LBW fetuses is LnBW = 1.470(BPD) + 0.0169(HC) - 0.0873(BPD)(2) + 0.00518(AC)(FL) and for macrosomic fetuses is Log(10)BW = 0.730(BPD) - 0.0375(BPD)(2) + 0.000264(AC)(FL). For LBW fetuses, the new method gave 7.6 ± 209.0 (g) of estimation error and 8.3 ± 7.8 (%) of absolute percentage error, while the best existing formula provided -0.7 ± 226.0 (g) and 9.1 ± 8.3 (%). With the new method, 71.3% of estimates fell within ±10% of the actual birth weight, while the best existing formula gave 65.5%. For macrosomic fetuses, the new method gave -87.9 ± 231.0 (g) of estimation error and 4.4 ± 3.9 (%) of absolute percentage error, while the best existing formula provided 115.6 ± 345.1 (g) and 6.8 ± 5.4 (%). With the new method, 89.1% of estimates fell within ±10% of the actual birth weight, while the best existing formula gave 75.6%.
To improve the weight estimation accuracy for low or excessive weight fetuses, separate formulas are necessary. The new method provides significant improvement on fetal weight estimation for LBW fetuses and macrosomic fetuses.
与正常出生体重胎儿（2500-4000 克）相比，对低体重或超重胎儿进行准确的胎儿体重估计对于预测胎儿窘迫和管理分娩更为重要。已经开发了新的公式来分别估计低出生体重（LBW）胎儿和巨大儿的体重。
本研究纳入了 523 例出生体重小于 2500 克的胎儿、652 例出生体重正常的胎儿和 239 例出生体重大于 4000 克的胎儿。评估并比较了 25 种现有的包含定期定义的胎儿测量值的公式。现有公式的性能评估表明，没有一种公式可以同时为 LBW 胎儿和巨大儿提供一致准确的体重估计。利用 1034 例病例生成了一个总体回归公式。如果预估计的体重落入可疑的 LBW 和巨大儿范围，则使用 LBW 胎儿和巨大儿的新回归公式更新该值。作为训练组，使用 262 例 LBW 胎儿和 120 例巨大儿进行逐步线性回归，以获得两个用于可疑 LBW 胎儿和巨大儿的更新回归公式。作为验证组，评估了另外 261 例 LBW 胎儿和 119 例巨大儿。
新的总体公式的形式为 Log(10)BW = 0.180(HC) + 0.00628(AC) - 0.00318(HC)(2) + 0.00173(AC)(FL) + 0.0000430(BPD)(HC)(2)。可疑 LBW 胎儿的更新公式为 LnBW = 1.470(BPD) + 0.0169(HC) - 0.0873(BPD)(2) + 0.00518(AC)(FL)，而巨大儿的更新公式为 Log(10)BW = 0.730(BPD) - 0.0375(BPD)(2) + 0.000264(AC)(FL)。对于 LBW 胎儿，新方法的估计误差为 7.6 ± 209.0（克），绝对百分比误差为 8.3 ± 7.8（%），而最佳现有公式的估计误差为-0.7 ± 226.0（克），绝对百分比误差为 9.1 ± 8.3（%）。使用新方法，71.3%的估计值落在实际出生体重的±10%范围内，而最佳现有公式为 65.5%。对于巨大儿，新方法的估计误差为-87.9 ± 231.0（克），绝对百分比误差为 4.4 ± 3.9（%），而最佳现有公式的估计误差为 115.6 ± 345.1（克），绝对百分比误差为 6.8 ± 5.4（%）。使用新方法，89.1%的估计值落在实际出生体重的±10%范围内，而最佳现有公式为 75.6%。
为了提高低体重或超重胎儿体重估计的准确性，需要使用单独的公式。新方法显著提高了 LBW 胎儿和巨大儿的胎儿体重估计精度。
