This is a good question! Normally, I would say that getting your child support order modified would require you to show changed circumstances of some sort before the court would change the order. Heading back to work after a divorce – especially if you have been a stay at home custodial parent – is definitely a change. But will the court modify the support order? It depends. For one thing, now that you have a new job, it means you will have more income. So in a way, your ex could have a point that it is they who should have a downward modification because your income will increase.
Initially, though, you may not have increased income because it could take a whole month to get paid at some workplaces. Added to that, even though you may have increased personal income, the babysitter will not come free and depending on how many hours you work, all that money could go to the babysitter (especially if you work part time.) So there is not net gain for you. There may even be a net loss.
So the answer is, it depends. It depends on how much you will make, how much the babysitter costs, what your ex’s situation is financially and how many hours you will be working. Things like that. For the most part the courts have a child support formula they use in determining your child support obligations and that of the other parent(s) involved. Deviating from that formula is rare and you would have to show the circumstances warrant deviation. Not so sure if the mere fact that you have a new job and have hired child care services would meet the standard. It really depends on your personal situation, I think.