The frequency of chromosomal abnormalities in reproduction is significant — 15 to 20 per cent of all pregnancies end in spontaneous abortion, and half of these miscarriages are associated with chromosomal abnormalities. In 1983, two UBC professors discovered a condition now known as confined placental mosaicism (CPM), where a chromosomal abnormality is present in the placenta but not the fetus. CPM allows a pregnancy that would otherwise spontaneously abort to continue to term, and is present in at least two per cent of pregnancies. In his earlier research, Paul Yong confirmed that some types of CPM increase the risk for poor fetal outcomes such as low birth weight or complications such as pre-eclampsia. Now he is studying how chromosomal abnormalities cause alterations in placental structure and function. The hope is to identify potential therapeutic interventions in pregnancies affected by chromosome abnormalities in the placenta.