Check with the doc, but it's probably entirely normal. I lost so much hair after having DD1 that the place was perpetually clogged with the stuff, and DP enquired if we'd secretly acquired a red setter.
My only tip for any further babies is to have your hair cut just before giving birth. I did before DD2 (makes me sound frightfully organised, it was all a bit of a coincidence) and it seemed to help a bit.