Hello dear, Thank you for your question. In my opinion, a vaginal bleeding that lasts for such a long period needs to be evaluated by an ob-gyn specialist. Please do not underestimate this condition, since it may lead to serious problems like: anaemia, hypotension etc. which can affect your health and your future baby as well. Rest assured that a single dose of steroids, no matter how big it is, cannot cause adverse effects on the menstrual cycle and therefore on your ability to conceive a child. I hope this helped. Best wishes, Dr. Alma.