WASHINGTON — Representative Sean P. Duffy, Republican of Wisconsin and one of the most recognizable faces of the Tea Party wave of 2010, announced Monday that he planned to resign from Congress next month, citing health complications of a baby he and his wife are expecting in October.

The imminent departure of Mr. Duffy is another blow to the Republican Party’s struggle to rebuild after crushing losses that swept it from power in the House. The announcement by Mr. Duffy, a former county prosecutor better known for his turn in the late 1990s as a star of the MTV reality show “The Real World,” follows a rash of retirements in recent weeks that have underscored the challenges and tribulations facing Republicans now serving in the minority.

For Mr. Duffy, the decision was deeply personal, he said Monday in a Facebook post. The lawmaker, who has eight children with his wife, Rachel Campos-Duffy, said they had recently learned that their ninth child, due in October, would have “complications, including a heart condition.”

“With much prayer, I have decided that this is the right time for me to take a break from public service in order to be the support my wife, baby and family need right now,” Mr. Duffy wrote. “It is not an easy decision – because I truly love being your Congressman – but it is the right decision for my family, which is my first love and responsibility.”