Question about Iron supplements (for all you health nuts!)

I just had my glucose test and everything looks great...except my iron is on the low side (not a shocker--I tend to be a little anemic even when I'm not pregnant). But here's my question:

My midwife recommended a 325 mg iron supplement. My husband was only able to find a "chelated iron 27 mg" supplement. I just want to know if the two are reasonably equivalent. I've done some sloppy research, but I have no idea what "chelated iron" is and how it compares to the standard ferrous sulfate that I've taken in the past.

About Elizabeth
Current: Augusta, Maine
Birth: December 31
On since: Jul 9, 2014
a college English teacher looking to transition to a career where I can work part time or from home to spend more time with my kids (one here, one on the way!).