a compilation of the results of 1918 antenatal karyotypings reported in the literature shows the following probability for the presence of an unbalanced chromosomal anomaly in the fetus : in mothers over age 40 4.25 % , in mothers age 35-39 , 1.45 % , in cases with trisomy-21 in a previous sibling 0.73 % , in cases with balanced chromosomal anomalies in the parents , 15.2 % .
C0013080
trisomy-21
C0008625
chromosomal anomalies