Approximately 1% to 2% of pregnancies involve chromosomal aberrations confined to the placenta. During the first few days of embryogenesis when fetal and placental lineages diverge, clonal expansion and mosaicism may occur, representing a potential pathological divergence from normal clonal dynamics of early embryogenesis. Mutations acquired during cell division may be identified and used to reconstruct embryonic lineage relationships that can reveal specific mutagenic processes affecting a tissue
