In my first pregnancy my dr made me take supplements and baby was born fine. I still had to take them for 3mths after for the anemia to go away tho. This time I had to have an iron infusion in hospital. So there's a lot they can do before it effects baby.
I took iron supplements with my first due to the doctors recommendations. I'll probably need them this time, but so far I haven't. Anemia can keep baby from getting enough oxygen, I believe. So it's good to follow your doctor's recommendations.
I just saw my hematologist as I am anemic as well. My hemoglobin is good but my reserve levels are low and I may need an iron infusion later in the pregnancy. He said closer to 26 weeks. I asked if it will affect the baby and he said no because our bodies give the baby the iron before we get it, that is why anemia is common for some pregnant women. Good luck.