A stillbirth happens when a fetus (unborn baby) dies while still inside the mother or dies during delivery (childbirth). It is said that the delivered baby is stillborn. Stillbirth is different from a miscarriage because a stillbirth happens after the baby has been living inside its mother 20 to 24 weeks (depending on the country). It is called a miscarriage if the baby lived inside the mother for less time.
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Stillbirth Facts for Kids. Kiddle Encyclopedia.