Objective: We sought to determine whether biochemical testing is a valuable adjunct to ultrasonography in selecting patients with fetal choroid plexus cysts for amniocentesis.
Study design: The study population consists of 128 patients who had fetal choroid plexus cysts detected during ultrasonography performed between 18 and 22 weeks' gestation. The patients had genetic counseling, and amniocentesis and biochemical testing were offered to all patients. The data were analyzed by dividing the patients into 3 groups. Group 1 had targeted ultrasonography only, group 2 had ultrasonography and maternal serum alpha-fetoprotein testing, and group 3 had ultrasonography and triple-screen (maternal serum alpha-fetoprotein, human chorionic gonadotropin, and estriol) testing. Outcome was determined by fetal karyotype or by neonatal examination by a pediatrician for patients who declined amniocentesis.
Results: There were 25 patients in group 1. Isolated choroid plexus cysts were detected in 20 fetuses, and all had normal outcomes. Additional anomalies were detected in 5 fetuses. Two had normal karyotypes, and 3 had trisomy 18. There were 52 patients in group 2. The maternal serum alpha-fetoprotein levels were normal in 44 patients, 41 of whom had isolated fetal choroid plexus cysts. Of these 44 patients, 40 had normal outcomes, and 1 patient had a fetus with trisomy 18. The remaining 3 patients with normal maternal serum alpha-fetoprotein levels had additional fetal anomalies on ultrasonography, but the karyotypes were normal. The maternal serum alpha-fetoprotein levels were abnormal in 8 patients, of whom 6 had fetuses with isolated choroid plexus cysts and normal karyotypes. Two patients had additional fetal anomalies detected on ultrasonography and had abnormal karyotypes, 1 with trisomy 21 and 1 with trisomy 18. There were 51 patients in group 3. Results of the triple screen were normal in 32 patients. The choroid plexus cysts were isolated in 29 of the 32 patients, and all 29 fetuses had normal karyotypes. The other 3 patients with normal triple-screen results had additional fetal anomalies on ultrasonography. One fetus had normal chromosomes, and 2 had trisomy 18. The remaining 19 patients had abnormal triple-screen results. Among them, 16 fetuses had isolated choroid plexus cysts, 13 of whom were normal, 2 had trisomy 18, and 2 had a de novo unbalanced translocation. The remaining 3 fetuses had additional anomalies, and all 3 fetuses had trisomy 18. There were 14 fetuses with significant chromosomal abnormalities. Nine mothers were <35 years old, and 5 were >/=35 years old.
Conclusions: This study shows the following: (1) The triple screen is a useful adjunct to targeted ultrasonography in selecting patients with fetal choroid plexus cysts for amniocentesis. (2) A normal triple-screen result and the absence of additional fetal anomalies on ultrasonography reliably exclude an underlying chromosomal abnormality, and amniocentesis is not indicated. (3) If the triple-screen result is abnormal, additional anomalies are seen on ultrasonography, or the mother is aged >/=35 years, then fetal karyotyping is recommended. (4) Patients who decline fetal karyotyping should have follow-up ultrasonography in 34 weeks' time.