Once the news started circulating among their friends (and her dad, thanks to Leonard), Penny faced pressure to give in and agree to have kids (although Amy eventually came to terms with never breast-feeding Penny’s baby, and vice versa).
Penny and Leonard decided to take a test to determine how compatible they are — a bit late, all things considered — which led to the reveal that Leonard wants kids but Penny does not.
The episode saw Raj seriously considering going ahead with an arranged marriage while Howard and Bernadette tried to pass their wisdom as parents and spouses along to their friends.
She was really very matter-of-fact about not wanting children.