good eats for you or baby?

Hi all. I have what might be a really silly question. Does having good/bad nutrition during pregnancy really affect the baby or is it mainly for the benefit of the mother? I heard somewhere that the baby will extract (bad choice of words) whatever nutrients it needs from the mother, whether she is eating well or not. For example, that's why so many women have dental issues after pregnancy because baby is sucking more calcium than what is being consumed.

Now whether this is true or not I'm not sure. Right now I would kind of like it to be considering my nausea is so bad the last few days I've barely eaten anything.