I don't quite get it : are you talking about Iron levels or Hemoglobin levels ?
Normal range for hemoglobin is 11.3 to 15 point something (g/dL) in women.
7 for hemoglobin is very low.
For my first child (HB), i had lost a LOT of blood, to the point that it was life threatening.
I was definitely anemic before the birth, but I hadn't done any tests (though I was on the verge of fainting most of the time, low blood pressure).
As it was a homebirth, I didn't get any blood transfer. Over a month after the birth, I finally got around to getting my blood count checked. I was in the lab, they took my blood, we left and wandered in town to do a couple of errands, when the lab called me on my cell phone to warn me that my hemoglobin levels were really low: 7. They were worried for me and asked me to come back in since I was still in town and they strongly advised me to see a doctor because 7 is at the limit of considering a blood transfer.
I definitely heard the "anemic before birth causes blood loss" story from a lot of people afterwards.
For my second child, I checked my blood count one month before my due date. I was at 10.6. Because I didn't want to risk anything I went on an iron rich diet (red meat every day, I usually don't eat much meat + a strong iron tablet). A week before my due date i checked my blood count again and my hemoglobin had rose up to 11,2!
My first midwife didn't ask for any blood tests, but for my second child, my midwives would have theoretically refused me should I have been under 10.