Drugan A, Sokol R J, Syner F N, Ager J W, Zador I E, Evans M I
Department of Obstetrics and Gynecology, Hutzel Hospital/Wayne State University, Detroit, Michigan 48201.
J Reprod Med. 1989 Dec;34(12):977-80.
Amniotic fluid alpha-fetoprotein (AF-AFP) was measured in 68 pairs of normal twins. Acetylcholinesterase (ACHE) was measured in 23 of those pairs. A significant difference in AF-AFP levels was found in 9/49 (19.4%) of twin pairs of the same sex and 9/19 (47.3%) of twin pairs of opposite sexes (P = .015). Differences in fetal size or gestational age at amniocentesis did not influence the rate of discordant AFP results. ACHE activity was identical in all amniotic fluid samples in twin pairs. In five additional patients, fetal anomalies (three), fetal death or fetal blood in the sample could have affected AFP levels, which were found to be discordant in three of them. Using fetal sex to represent zygosity, the study indicated that discordance in AF-AFP is more common in dizygous twins. The odds ratio for having a discordant AFP result if twins are of different sexes was 4.0. Implications of our data are: (1) in same-sex twins, discordance between sacs is less common, even if only one fetus is affected; (2) the difference in AFP results in twins of the same sex and of different sexes suggests variability in AFP transfer between twin gestational sacs; and (3) ACHE readily diffuses between sacs and cannot be used to determine which twin has an abnormality.
对68对正常双胞胎的羊水甲胎蛋白（AF-AFP）进行了检测。在其中23对双胞胎中检测了乙酰胆碱酯酶（ACHE）。在同性双胞胎中，9/49（19.4%）的双胞胎对AF-AFP水平存在显著差异；在异性双胞胎中，9/19（47.3%）的双胞胎对AF-AFP水平存在显著差异（P = 0.015）。羊膜穿刺术时胎儿大小或孕周的差异并未影响AFP结果不一致的发生率。双胞胎对的所有羊水样本中ACHE活性均相同。在另外5例患者中，胎儿异常（3例）、胎儿死亡或样本中存在胎儿血液可能影响了AFP水平，其中3例AFP水平不一致。以胎儿性别代表合子性，该研究表明AF-AFP不一致在双合子双胞胎中更为常见。如果双胞胎性别不同，AFP结果不一致的优势比为4.0。我们的数据的意义在于：（1）在同性双胞胎中，即使只有一个胎儿受到影响，囊间不一致也较少见；（2）同性和异性双胞胎中AFP结果的差异表明双胎妊娠囊间AFP转移存在变异性；（3）ACHE很容易在囊间扩散，不能用于确定哪个胎儿存在异常。
