MATERNAL SERUM ANALYTE LEVELS IN PREGNANCIES WITH FETAL DOWN-SYNDROMERESULTING FROM TRANSLOCATIONS

OBJECTIVE: Our purpose was to determine whether pregnancies affected b y fetal Down syndrome resulting from Robertsonian translocations are a ssociated with second-trimester maternal serum analyte levels differen t from those resulting from fetal trisomy 21. STUDY DESIGN: Pregnancie s with Down syndrome caused by Robertsonian translocations were identi fied through the cytogenetics laboratories at the participating instit utions. Those with maternal serum screening values between 15 and 20 w eeks were evaluated. RESULTS: Eleven cases of fetal Down syndrome caus ed by Robertsonian translocations were identified. The median alpha-fe toprotein, unconjugated estriol, and human chorionic gonadotropin leve ls were 0.68, 0.67, and 2.83 multiples of the median, respectively. Th ese analyte levels are similar to those for fetal trisomy 21. CONCLUSI ONS: These data suggest that Down syndrome resulting from either Rober tsonian translocations or trisomy 21 will be detected in a similar per centage of cases because the second-trimester maternal serum analyte l evels are similar.