It's Garry Shandling's Show (1986)

S2E1 Who's Poppa?

Jackie discovers she's expecting, but Pete is plagued by doubts about his paternity. As tensions rise, he grapples with the possibility that he may not be the biological father of her child, leading to a series of misunderstandings and emotional turmoil. Jackie, on the other hand, is determined to prove Pete’s place in their future, regardless of the child's parentage. The couple must navigate their relationship through uncertainty, ultimately seeking clarity and connection amid the chaos of impending parenthood.