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Teen Mom's original cast members are moving on.

The upcoming fourth season of the hit MTV show that follows Maci Bookout, Amber Portwood, Farrah Abraham and Catelynn Lowell, will be the girls' last, Us Weekly reports.

"They will continue o be a part of our MTV family, and we're thankful to these brave young women for sharing their stories and helping to make a positive impact on teen pregnancy prevention," and MTV rep said.

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Bookout, Portwood, Abraham and Lowell were all cast members in the first season of 16 and Pregnant, which premiered in 2009. The unscripted series followed the pregnant young women and the challenges they faced as young moms. It eventually turned into the spin-off, Teen Mom.

"From appearing in a series of teen pregnancy prevention PSAs to speaking at high schools around the country, these young women have become advocates for this issue," an MTV rep said in a statement.

The  premiere date for the show's fourth season has not been announced, but it will likely air in summer 2012.