The chorion is the outermost layer of the fertilized ovum (zygote) that furnishes a protective and nutritive covering and produces the amniotic fluid. The amniotic fluid protects the |embryo| and |fetus| during |pregnancy| and the rupture of the amniotic sac is one of the first signs that labor has begun. During |childbirth| the amniotic fluid lubricates the cervical canal, facilitating the passage of the head of the |fetus| through the cervical canal.
