Wald N, Cuckle H, Boreham J, Terzian E, Redman C
Br J Obstet Gynaecol. 1981 Nov;88(11):1094-6. doi: 10.1111/j.1471-0528.1981.tb01759.x.
In 902 singleton pregnancies, maternal serum alpha-fetoprotein (AFP) levels between 15 and 20 weeks of pregnancy were significantly related to maternal weight (r = 0.24, p less than 0.0001). Lighter women had on average higher AFP levels than heavier women, perhaps on account of the greater concentration of AFP in their relatively smaller volume of blood. The mean AFP level for women weighing less than 45 kg was 68% higher than the mean level for women weighing 85 kg or more. Maternal weight was found to be an important factor which could account for false positive AFP results in antenatal screening for open neural tube defects. A policy of adjusting maternal serum AFP values according to maternal weight among women with borderline positive results could reduce the number having a diagnostic amniocentesis with only a negligible loss of detection for open spina bifida. With such a policy, using a cut-off level of 2.5 x normal median, the false positive rate in the 902 women screened would have been reduced fom 2.8% to 2.0%.
在902例单胎妊娠中，孕15至20周时孕妇血清甲胎蛋白（AFP）水平与孕妇体重显著相关（r = 0.24，p＜0.0001）。体重较轻的孕妇平均AFP水平高于体重较重的孕妇，这可能是因为在她们相对较少的血量中AFP浓度更高。体重小于45千克的孕妇平均AFP水平比体重85千克或以上的孕妇高出68%。发现孕妇体重是导致产前开放性神经管缺陷筛查中AFP假阳性结果的一个重要因素。对于临界阳性结果的孕妇，根据体重调整其血清AFP值的策略可以减少进行诊断性羊膜穿刺术的人数，同时对开放性脊柱裂的检测损失可忽略不计。采用这样的策略，将临界值设定为正常中位数的2.5倍，在接受筛查的902名女性中，假阳性率将从2.8%降至2.0%。
