It is quite normal for women to have some blood in their urine at various stages of their menstrual cycle, so I would think quite normal for it to occur during pregnancy.
Are you having any stinging, itching when you wee? Or weeing more than usual? Does it smell?
If not, then I wouldn't worry too much, and mention it at your next appointment. If you are worried I would call the midwives at your local hospital.