She’s currently 39, so it seems like even kickass!Leslie Knope would have a really, really hard time getting pregnant accidentally at that age if she were still on the pill.
And where the show’s canon had them at least mention the idea of starting a family after Jerry’s retirement, it seems that because of the recall thing going on, they would have agreed that it would be a lousy time to start (stress, not knowing what was going to happen, etc…) but when they were in Paris they spent a night really discussing it (over macaroons and a bottle of red wine). And they decided to start trying for real. She went off the pill not too long after they got back from their trip.
They both knew that it might take a while because of her age (Ann had tried to prepare Leslie by suggesting it might take up to a year, and of course Leslie was all, “Oh, I can do it in six months. Just watch. Plus, I’m sure Ben has awesome sperm.”) Also, Ben made her promise to try and not to get too worked up about it not happening quick enough-that making a baby was supposed to be fun and not stressful.
She was doing pretty good with all that but then just a few months into their whole doing it as often as possible baby-making plan the NPS job offer happened and Leslie got cold feet about the timing of getting pregnant. She started to backtrack a little, wanting to wait until she made a decision about the job and then maybe until they were settled in Chicago, etc… Ben saw that easily spiraling out of control and there never being a “good time”-but at the same time, he does believe that it’s her body and she has the veto power on their family planning. So, even though they didn’t exactly agree about waiting until she decided about the job, they never really fought about it or anything, and when they did discuss it, he deferred to her wanting to postpone their actively trying to get pregnant.
She didn’t go back on the pill, but they started using condoms most of the time after the job offer (of course there were a few sexy, heat-of-the-moment type times where even she was like, “fuck it, let’s just do it. God, Ben, get in my already!”)
So when she was in the drugstore with Andy and the pharmacist said she didn’t have the flu, it didn’t take that long for her to put the pieces together (especially since they were a tiny bit lazy with the condom use over the past couple of months and she was actually a few days late-which Leslie had assumed was because she was freaking out over the job offer and the Unity Concert details).
But as soon as she saw the pregnancy test display it kind of clicked.
That said, I don’t think she really, really, really expected it to be positive but when it was she was very happy right from the start. Also, she was a little freaked out when she couldn’t get a hold of Ben all day after he drowned his phone at the winery. Leslie started thinking about how maybe using a 99 cent on-sale pregnancy test wasn’t that reliable and since she wanted to be absolutely positive before she told Ben, by the time he had gotten home, she had taken another test (a different brand) at home-also positive.
After she told him, she was all, “So, I bought one more test (a third brand) as a back-up and I’m going to have to pee again eventually tonight. You wanna do this one together?”
BONUS HC: The first time Leslie pee din front of Ben
While Leslie was suspended after her trial and hanging out at Andy and April’s a lot, there was one morning when Ben was taking a really long time brushing his teeth (after April and Andy had already left for work) and Leslie had to pee super bad but there was only one bathroom and she just didn’t care-just barged right in and started peeing. And he was all flustered.
"Leslie, I’m still...Okay. Okay. That’s okay. We really are doing this whole relationship thing for real now, huh? Okay."
She’s still peeing. Kind of glaring at him.
"Wow. How long were you...holding that for? Um, sorry." He puts the toothbrush back in his mouth and stops talking. Tries not to watch.