A sudden case of fetal heartbeat stopping can sound strange and you might not be able to believe it, but it is actually quite common and most of the time, it is because of the chromosomes. Here are a few common reasons why this happens: Chromosomal: A lot of missed miscarriages have been known to happenbecause of fetal anomalies or because of the baby’s chromosomes. This happens due to an irregular sperm or an abnormal egg, or a blend of the two. When the chromosome divides and leads to a pattern in the zygote, it leads to abnormalities. In such cases, the body fights back and tends to abort the infant before the pregnancy reaches the fetus stage. Blood Clots: Sometimes the mother might have thrombophilia, which causes blood to thicken in the body. Because of thrombophilia, the mother might experience clots in some veins of the umbilical cord or placenta. This affects the bloodstream and prevents the fetus from getting enough oxygen and blood, causing the heartbeat to stop. Cord Twist: In some cases, the umbilical cord gets twisted around the limbs or neck and stops the oxygen and blood supply to the embryo. This stops the heartbeat suddenly.