It could be implantation but it's always good to just ring the hosp and let them ask all the right questions of you.

What color was the blood, were there large amounts etc?

I found that DTD caused me to bleed during my pregnancy with DD, i had 6 scares in total but she was fine, mine was brown with small spots of redish pink, this PG i haven't had 1 bleed... odd though.

I hope everything is ok and it's just implantation, take it easy and maybe give your Dr a call.