Since two-thirds of all miscarriages occur within the first trimester of pregnancy, it's by no means impossible or even all that unusual for a woman to have a miscarriage and not know it -- especially if her menstrual cycle is somewhat irregular, since this might make her less likely to attribute a tardy or missed period to pregnancy. In fact, one study suggests that perhaps as many as 25% of all miscarriages take place within the first six weeks of pregnancy before many women would have reason to think that they might be pregnant..<br />
The only instance I can think of in which I think a woman would know that she's had a miscarriage without knowing that she was pregnant would be one of those very unusual cases where the woman is so deeply in denial about her own pregnancy that she attributes the symptoms to another cause (such as blaming skipped periods and a heightened emotional state on stress) or blocking them out of conscious awareness altogether. If such a woman suddenly began to hemorrhage and experience severe abdominal pain, she would almost certainly consider this an emergency -- or at least one would hope so! -- and go to the emergency room where it's probable that the doctors would discover she had been pregnant and miscarried.
I miscarried at about 2 - 2.5 months into my pregnancy. I always have painful periods with a lot of bleeding, but the miscarriage cramps and bleeding were somewhat worse. If I would have miscarried sooner I probably wouldn't have noticed at all. I think those lucky girls who have light periods, little bleeding and light cramps are incapable of understanding how anyone could not know they've miscarried during the first weeks.
the warning signs are: severe onset of cramping, spotting and lower abdomin pain that is experienced after a missed period. u should seek medical attention if these symtoms present themself. It is possible for a misscarrige to cause internal bleeding.