DMPK and myotonic dystrophy type 1: Standard repeat-spanning or flanking PCR to detect the normal DMPK allele of the affected parent is commonly employed in PGT-M for DM1 due to reliability issues in detecting the expanded allele, especially when performed directly on the limited genetic material of single cells (Sermon et al., 1997, 1998; Dean et al., 2001; Piyamongkol et al., 2001; Kakourou et al., 2007, 2008).