Yes if haemoglobin is low the baby's weight gain in the womb is compromised. Also during birth you loose blood and haemoglobin falls further which can make you feel weak and affect your blood pressure. The IV method is safe so go ahead and take it.

I was given iron drips to increase my haemo levels, check with your doctor. If your haemo is low, ur baby might have much less level.

instead of blood transfusion you can take iron injections which is more safe. don't worry it will not affect the baby