I'm trying to keep running as far into my pregnancy as possible. I'm even doing an occasional (short) race! Obviously, it's been a fun hobby of mine for a while, and I'll be sad when eventually (whether that's at 6 months or 8.9 months) it will end up becoming too uncomfortable for the time being (and hopefully it'll be my choice to make, and no complications will make it inherently unsafe). But as much as I appreciate any time I get to enjoy it, there are definitely both pros and cons to continuing to run.
Con: No matter how many times you go to the bathroom before your run, you'll still start feeling like you have to pee no more than 10 minutes into your run.
Pro: But you know the real reason you make sure to use the bathroom before a run? No longer that crucial. The lovely pregnancy symptom of constipation (which has actually been fairly mild for me) means even all the jiggling of your intestines on a run no longer makes a bathroom stop for #2 even remotely urgent.
Con: It can be a bit disheartening to know you're not going to set any PRs, and will in fact probably be getting slower each week.
Pro: You don't have to train for a PR. No need to follow a set schedule - do whatever you feel like doing. A nap feels more appealing than a 5 miler? No problem, take nap! No need to do quarter mile repeats literally as fast as you can, pushing yourself to the limit of having to catch your breath. You get to just do the easy, fun, relaxing running. (Or push yourself when you feel like it, but only when you truly feel up for it.)
Con: None of your cute running shirts fit you anymore.
Pro: You finally have a use for the unisex or just too big (cause standardized sizing is apparently just too much to ask for) race shirts you've accumulated.
Con: In part due to those unisex race shirts, you spend a large portion of early pregnancy with a stomach that maybe kinda looks like you're pregnant, but could very easily just bea little extra weight. So presumably everyone who sees you run - so incredibly slowly - is assuming that you're a brand new runner trying to run off that beer gut.
Pro: Eventually, you'll have an obvious baby bump, and it will make sense to everyone why you're chugging along so slowly.
Con: Even if you want to challenge yourself, do some races, keep up with a modified race goal - your body often just isn't having it. Some days it's just going to be a slog fest no matter what.