Most miscarriages involve the body quickly acting to expel the fetal tissues, causing the mentioned symptoms including bleeding, cramping, or contraction-like pain. Women who are going through an active miscarriage will bleed more than they do during a menstrual period and will also pass clots and tissues in addition to blood.
I could see a clearly recognizable amniotic sac with a very tiny fetus during one miscarriage, for instance. It is possible to have a miscarriage without symptoms in so far as it is possible for a baby to pass away in utero without the body commencing the process to expel fetal tissues. This is called a missed miscarriage or a silent miscarriage, and though the causes are not clear, it can happen to any woman suffering a miscarriage that the baby remains in utero. In this case, a woman may not be aware that there is anything wrong until she starts developing symptoms, has a routine ultrasound at a prenatal appointment, or noticed a lack of pregnancy symptoms.
In the case of a missed miscarriage, once you find out, your doctor is likely to recommend either a D&C or inducing a miscarriage with certain medications like misoprostol, depending on the available options and the duration of your pregnancy. A D&C is a small surgical procedure in which your uterus is emptied. This is normally done under local anesthesia. There are risks involved with allowing a dead fetus to remain in the body for too long, such as infection, so it is important to discuss the options and decide what to do.