That is the topic of my latest Bloomberg column, here is one bit:

There is in fact a pronounced “baby bump” in December. The numbers show that induced deliveries and scheduled Caesarian section deliveries are higher than average toward the very end of the year.

Why? In the US, there are significant tax advantages to having a child. If you are a single parent with an adjusted gross income below $112,500, an extra child brings you a $3,600 child tax credit per year.

So — speaking strictly about the tax implications, of course — a New Year’s Eve baby is better than New Year’s baby: You can claim that little bundle of joy as a dependent for the entire year, even though they were only there for a day of it. Yet further benefits could come from state-level earned income tax credit and child tax credit programs.

You might argue that the parents, not the kids, gain the most from these tax benefits. You might also ask if there are some costs to these newly born children. In fact, the study shows that these children have lower birthweights. Further research shows that the accelerated births had noticeable impacts on the children, again finding lower birthweights.

The good news, however, is that those same kids have accelerated weight gains over the course of subsequent examinations. The further good news is that those children reach early development milestones at a faster pace than average. That may reflect the extra income the parents have, since higher income and other positive parental features do predict better developmental outcomes for the kids.

Don't wait until April!