Beckwith–Wiedemann syndrome is an overgrowth syndrome with elevated PW and BW49 where approximately 50% have lost maternal-specific methylation at the putative imprinting control region 2 (ICR2) within intron 10 of KCNQ1 that is also the transcriptional start site of the regulatory long noncoding RNA KCNQ1OT1 (ref. 50) controlling expression of CDKN1C and KCNQ1. The location of the lead signal, rs2237892, to this region suggests that it influences PW through an effect on methylation at ICR2 in the placenta. Here, KCNQ1 is linked to overgrowth syndrome.