Week 24

The unsung hero of the fetal support system is the umbilical cord, which forms a vital link between the fetus and the placenta. The cord contains two arteries and one large vein; by birth, it may measure up to four feet long. Every 30 seconds, nutrients and oxygen-rich blood are transported from the placenta to the fetus via the single vein, then back again to the placenta through the two arteries. This ingenious method ensures a constant supply of filtered air and nutrients, and keeps the mother's blood separate from the baby's.