Pete Wentz's girlfriend reportedly suffered a miscarriage over Christmas.

Meagan Camper's grandmother Sherrilyn Camper claims the couple lost their unborn child in December.

According to Sherrilyn, the brunette model struggled with the pregnancy and needed more support from the Fall Out Boy star.

"[He] abandoned her right off the bat... He wasn't very much help, that's for sure," she told US publication Star.

Rumours that Meagan was expecting began circulating at the end of last year.

However, a spokesperson for Pete stated the reports were "absolutely not true" and that the beauty was definitely not pregnant.

Pete began dating Meagan last September following his separation from actress-and-singer Ashlee Simpson in February 2011.

The pair have been spotted enjoying days out with the rocker's three-year-old son Bronx Mowgli from his marriage to Ashlee.

Pete has previously stated he loves fatherhood and would like to expand his family.