Delozier-Blanchet C D, Extermann P, Morris M A, Engel E
Institut Universitaire de Génétique Médicale, Genève.
J Genet Hum. 1989 Jan;37(1):61-9.
As of December 1, 1988, we had, as part of our prenatal diagnostic service, studied 458 transcervical chorionic villus biopsies. Three-fourths of these samples were taken because of advanced maternal age (greater than or equal to 35 years), whereas nearly one fifth were done to alleviate parental anxiety. The remainder were performed because of a precedent chromosomal anomaly in child or parent, to determine fetal sex in the case of X-linked familial disorders, or to obtain DNA for molecular analyses. Among the cytogenetic anomalies detected after 24 to 48 hours of culture, eight involved classical trisomies. In four other instances the chromosomal abnormalities were more difficult to interpret (mosaic trisomies 10, 13 and 15, an apparently uniform trisomy 7). All four were revealed to be "false positives", since neither the amniocenteses nor the karyotypes of the normal newborns (one pregnancy is still ongoing) confirmed an abnormal karyotype. In the case of the trisomy 7 we were able, after birth of the baby, to study two placental biopsies, one of which revealed an abnormality distinct from that detected in the chorionic villi. The observations concerning a fifth false positive are more worrisome, as an apparently uniform trisomy 18, with a fetus showing growth retardation on ultrasound, could not be confirmed in the abortus. Otherwise, we have not encountered a false negative result. In this article we discuss the mechanisms potentially responsible for the cytogenetic discrepancies sometimes observed between fetal and placental tissues. Molecular analyses may help to establish whether a chromosomal anomaly present in fetal chorionic villi had its origin in the pre- or post-zygotic stage; in the latter case the aneuploidy may be uniquely extrafetal.
截至1988年12月1日，作为我们产前诊断服务的一部分，我们对458例经宫颈绒毛取样进行了研究。这些样本中，四分之三是因为孕妇年龄偏大（大于或等于35岁）而采集的，而近五分之一是为了缓解父母的焦虑。其余的样本采集是因为孩子或父母之前有染色体异常，在X连锁家族性疾病的情况下确定胎儿性别，或者获取DNA进行分子分析。在培养24至48小时后检测到的细胞遗传学异常中，有8例涉及典型三体。在另外4个案例中，染色体异常更难解释（10号、13号和15号染色体的嵌合三体，以及一个明显一致的7号染色体三体）。所有这4例都被证明是“假阳性”，因为羊水穿刺检查和正常新生儿的核型分析（有一例妊娠仍在进行中）均未证实核型异常。对于7号染色体三体的情况，婴儿出生后，我们能够对两份胎盘活检样本进行研究，其中一份显示出与绒毛取样中检测到的异常不同的异常情况。关于第五例假阳性的观察结果更令人担忧，因为一个明显一致的18号染色体三体，其胎儿在超声检查中显示生长迟缓，但在流产胎儿中未能得到证实。除此之外，我们没有遇到假阴性结果。在本文中，我们讨论了胎儿组织和胎盘组织之间有时观察到的细胞遗传学差异的潜在原因。分子分析可能有助于确定胎儿绒毛膜绒毛中存在的染色体异常是起源于合子前还是合子后阶段；在后一种情况下，非整倍体可能仅存在于胎儿之外。
