We recently had our third bub, as after our second son was born I just knew I wasn't finished. It did take DH a while to think it through and decide to TTC #3 but he ultimately gave it the green light (to my joy!).
I was more concerned about conceiving given my age (38 going on 39 at the time), and it did actually take nearly 12 months - including four (failed) clomid cycles and the assistance of accupuncture/chinese herbs (which did the trick).

Then when I did conceive I discovered I had progesterone issues, which I didn't have with my first two kids. Fortunately the progesterone pessaries were sufficient, and I went on to have a successful pregnancy. I was glad to have the 12-week and 20-week scans out of the way, as while I didn't exactly worry about issues with the bub, it was peace of mind to know bub was as healthy as could be expected from u/s and BTs alone.

My next concern was whether an Ob would consider me higher risk because of my age ... and for this reason I ditched going private to go public. For whatever reason, I just felt like I'd be treated as more "normal" in the public system. There was probably no basis for this thinking - I was/am healthy, around the right weight for my height and not had an issue with previous pregnancies/births. Regardless, I was happy to go public this time and save some $ along the way.

DS3's birth was fabulous, the midwives were brilliant and all-in-all my pregnancy care and birth was great.

As for the dynamic of three, well ... we're still finding our feet. My other two boys are almost 5 (in March) and 3 next month. Some days it's completely chaotic, particularly when DS3 can't settle very well and/or catnaps and DS1 and DS2 are being rowdy and/or naughty. And there are times I could pull my hair out. But as I said, we're learning and we'll get there.

The main thing though, is that when I snuggle my dear little DS3 I know we made the right decision to have three. Yes, I would have loved a little girl (didn't set my heart on it though) but my littlest boy is an absolute delight. His two older brothers virtually smother him with love, and while both definitely attention seek a little more than usual at the moment, they keep telling me (spontaneously) that they love their baby brother. And given my three boys are all aged under 5, I'm hoping that they'll be good mates.

So for our family, having three kids has so far been the right move. Sometimes I catch myself thinking "awww, he's my last and I'll never go through this again", but in my heart-of-hearts I know I'm happy with three.