These problems can also cause premature birth (when a baby is born earlier than expected). One study found that 19% of second-trimester miscarriages were caused by problems with the umbilical cord. The fetus gets blood and oxygen through the umbilical cord. Every part of the body needs blood and oxygen to survive. If the baby cannot get enough oxygen because of a problem with the cord, it can die. Problems with the placenta may also cause second-trimester miscarriages. Nutrients and blood pass through the placenta in order to get from the mother to the umbilical cord. The placenta also helps filter out some things that could hurt the fetus. If there is a problem with the placenta, the fetus could die because it did not get enough nutrients and oxygen, or because the placenta did not filter out harmful things.