It's normal. Even when you're pregnant, you can lose blood at the time when you would normally have your period! This bleeding is due to changes oestrogen levels. Bleeding is generally light and doesn't last for more than one or two days.
"
Bleeding occurs in 20% of normal pregnancies at the beginning", indicates obstetrician Dr Frydman.
However, if bleeding occurs at the start of your pregnancy
not at the time when you would usually have your period, it could also be a sign of complications such as
ectopic pregnancy, or even a
miscarriage. Check with your doctor. And if bleeding
persists, see your doctor as soon as possible.