An unexpected high frequency of trisomic fetuses in 229 pregnancies monitored for advanced maternal age.
In 229 pregnancies monitored because of advance maternal age, 16 (7%) abnormal fetal karyotypes were detected. We found 13 cases of trisomy 21, twice a trisomy 18, and once an additional marker chromosome. The frequency of abnormal fetal karyotypes in different maternal age groups was found to increase from 1:20 at 38--40 years, to 1:16 at 41--43 years, and finally to 1:4.5 in women of 44--46 years. The overall incidence of chromosomal aberrations and specifically of trisomy 21 is considerably higher than that described in retrospective studies.
D000328:Adult; D002902:Chromosomes, Human, 16-18; D004314:Down Syndrome / Q000209:etiology; D005260:Female; D006801:Humans; D008423:Maternal Age; D008875:Middle Aged; D011247:Pregnancy; D014314:Trisomy