Published online by Cambridge University Press: 15 January 2010
In 1971 Shettles postulated that, during pregnancy, chorionic cellular elements from degenerating villi were shed into the endocervical canal and could be analysed to assess fetal sex. Accordingly, he retrieved transcervical cells (TCC's) with cotton swabs and tested them for the presence of the Y chromosome using a fluorescent dye (quinacrine mustard). At the time of publishing his note, he had correctly diagnosed the sex of 10 fetuses in 18 pregnancies investigated.