Passing very small (ex. tip of your finger) blood clots during your period is normal and many women do not ever feel them exiting their bodies. Other women will feel a clot come out after standing up from a chair, getting out of bed, or using the bathroom. Passing period clots is usually uneventful, however, large blood clots can not pass out of the uterus without the cervix dilating which can cause strong cramping and pain.