Regine Chassagne and Win Butler (QMI Agency file photo)

Arcade Fire frontman Win Butler and his bandmate wife Regine Chassagne are set to become parents, according to reports.

Chassagne, a vocalist and multi-instrumentalist for the Grammy Award-winning group, is said to be expecting her first child with Butler, who she married in 2003.

The news emerged after Chassagne debuted a large baby bump when the rockers took the stage in their native Montreal, Canada, for a charity concert on Saturday.

Chassagne has yet to comment on the rumours, but if proved true, she joins Arcade Fire's pregnant touring violist Marika Shaw in the expectant mother club.