Number of Dependents

In March, I had a baby. Do I need to change the number of dependents I claim throughout the year (with whom I change through my HR person at work)? 

 

I am under the impression that the more you claim during the year, the less money the government takes out of each check, resulting in a bigger refund at the end of the year; and the less you claim during the year, the more money the government takes out of each check, resulting in a smaller refund come tax time. Is that correct?