All blood contains a clotting factor. To enable menstrual blood to flow freely from the uterus and leave your body without clotting, the uterus produces an anti-clotting agent. If the menstrual loss is heavy, it is possible that the anti-clotting agent will be used up before a period has finished, so that the remaining blood is likely to form clots. However with them being quarter size clots, this is too much. If this lasts for more than one day, then I do advise to see your doctor for further evaluation.
Some common causes for heavy bleeding can include hormonal imbalance, Uterine fibroid tumors, Endometrial polyps, PID, Cervical polyps. It may be menopause related, which a blood test can confirm this as well. So do make an appt. If the clots continue, then do also be seen.
Best of luck Hun, Hope this helps, If you need anything else please feel free to ask. If you found this helpful don’t forget to click the *ACCEPT* button and leave *POSITIVE* feedback.