The second-trimester fetus with isolated choroid plexus cysts: A meta-analysis of risk of trisomies 18 and 21

Objective: To assess the risk of trisomy 18 and trisomy 21 associated with isolated choroid plexus cysts diagnosed by ultrasound in the second trimest er. Methods of Study Selection: We reviewed the unabridged PREMEDLINE and MEDLI NE databases for articles written in the English language regarding second- trimester fetal isolated choroid plexus cysts and trisomies 18 and 21, publ ished in the period 1987-1997. Selection criteria included only second-trim ester, prospective studies in which the rate of fetal isolated choroid plex us cysts could be calculated, the number of fetuses with trisomy 18 and 21 was reported clearly, and pregnant women of all ages were included, rather than only those at high risk for aneuploidy due to advanced maternal age. Tabulation and Results: Thirteen prospective studies, comprising 246,545 se cond-trimester scans, were selected. Among 1346 fetuses with isolated choro id plexus cysts, seven had trisomy 18, and five had trisomy 21. For each st udy, a 2 x 2 table was constructed and the likelihood ratio of a positive t est was computed. The likelihood ratios for trisomies 18 and 21 were found to be homogeneous (P = .08 for trisomy 18, and P = .16 for trisomy 21). The summary likelihood ratio and 95% confidence interval (CI) for each chromos omal abnormality were calculated using the Mantel-Haenszel fixed effects mo del of meta-analysis. The summary likelihood ratio for trisomy 18 was 13.8 (CI 7.72, 25.14, P < .001) and for trisomy 21 was 1.87 (CI 0.78, 4.46, P = .16). Conclusion: The likelihood of trisomy 18 was 13.8 times greater than the a priori risk in fetuses with isolated choroid plexus cysts diagnosed in the second trimester. However, the likelihood of trisomy 21 was not significant ly greater than the a priori risk with isolated choroid plexus cysts. The d ata supported offering pregnant women karyotyping to rule out trisomy 18 wh en maternal age at delivery is 36 years or older, or when the risk for tris omy 18 detected by serum multiple-marker screen is more than one in 3000. ( Obstet Gynecol 1999;93:869-72. (C) 1999 by The American College of Obstetri cians and Gynecologists.).