It means there is problem with the chromosome genetics of the fetus and it’s the nature way of stopping it from further development. The gynae will do the removal of fetus through vacuum suction method or prescribed medication to induce the fetus out. The medication method will cause severe menstrual pain similar to labour.
This means the genetic material in the chromosomes wasn't right for a baby to develop. In a missed miscarriage, either the embryo doesn't develop, or it doesn't get very far and the heartbeat stops. Occasionally it happens beyond the first few weeks, perhaps at eight weeks or 10 weeks, or even further on.