Can I Have a Tummy Tuck if I Plan on Having a Second Baby in 5 Years?

You have hit on the main reason why we do tummy tucks: After pregnancy, no amount of exercise or diet will restore loose skin especially if there are stretch marks, or re-align the muscles if they have been separated. If you do have a tummy tuck and then become pregnant, it should not have any adverse effect on the pregnancy but you will lose the benefit of having the tummy tuck, and a second one later can be a lot more difficult. It isn't as simple as just having to have another tummy tuck, so my advice is to wait.

Most plastic surgeons would recommend that you wait until you are done having children before having a tummy tuck.  Probably the most effective part of the procedure involves tightening of the abdominal midline muscles and this repair would be disrupted with an additional pregnancy. 

If you are simply interested in addressing loose skin, a skin-only tuck could be performed but this would not give you as dramatic a result and as flat an abdomen as a traditional tummy tuck.

I would wait!

I hope this helps!