Senior Obstetrician, Department of Obstetrics and Gynecology, and Senior Geneticist.
Head, Genetics Institute, Carmel Medical Center.
Obstet Gynecol Surv. 2017 Oct;72(10):603-609. doi: 10.1097/OGX.0000000000000490.
Lower than expected first-trimester crown-rump length (CRL) is a common sonographic finding, usually leading to reassessment of gestational age.
The aim of this study was to perform a meta-analysis defining the risk of chromosomal aberrations in pregnancies with decreased first-trimester CRL.
A search was conducted by a research librarian in 5 databases, with no time or language restrictions. Original researches examining the risk of chromosomal aberrations in pregnancies with low CRL were selected. The effect estimates were presented as odds ratios with 95% confidence intervals).
Following screening of 3894 references, 12 articles were selected. Only 2 articles directly fulfilled the review goals, comparing the rates of chromosomal aberrations in small-CRL versus normal-CRL fetuses. Combined analysis of these 2 studies, encompassing a total of 403 fetuses with small CRL and 4047 control pregnancies, yielded an odds ratio of 5.54 (95% confidence interval, 1.2-26.1) for abnormal karyotype in small-CRL fetuses. Ten studies compared CRL in fetuses with specific chromosomal aberrations to pregnancies with normal karyotype, yielding a significant growth delay in fetuses with trisomy 18 (6 of 7 articles) and triploidy, but not in fetuses with trisomy 21. Overall quality of evidence was rated as "very low" using Grading of Recommendations Assessment, Development and Evaluation criteria.
Our review results indicate that low first-trimester CRL might be associated with a significantly increased risk of chromosomal anomalies. Thus, invasive prenatal testing or cell-free DNA screening might be offered in such pregnancies, particularly if dating is certain.
低于预期的孕早期头臀长（CRL）是一种常见的超声表现，通常导致重新评估孕周。
本研究旨在进行荟萃分析，确定头臀长降低的妊娠中染色体异常的风险。
研究人员在 5 个数据库中进行了检索，无时间和语言限制。选择了检查头臀长低的妊娠中染色体异常风险的原始研究。将效应估计值表示为比值比（95%置信区间）。
在筛选了 3894 篇参考文献后，选择了 12 篇文章。只有 2 篇文章直接满足了综述目标，比较了小 CRL 与正常 CRL 胎儿的染色体异常率。对这 2 项研究进行综合分析，共纳入 403 例小 CRL 胎儿和 4047 例对照妊娠，小 CRL 胎儿异常核型的比值比为 5.54（95%置信区间，1.2-26.1）。10 项研究将 CRL 与特定染色体异常的胎儿进行比较，与正常核型的妊娠相比，18 三体（7 篇文章中的 6 篇）和三倍体胎儿存在明显的生长延迟，但 21 三体胎儿则没有。使用推荐评估、制定和评估标准对证据质量进行总体评价，结果为“极低”。
我们的综述结果表明，孕早期头臀长降低可能与染色体异常的风险显著增加相关。因此，在这种情况下可能需要提供侵入性产前检测或游离胎儿 DNA 筛查，特别是如果确定了预产期。
