Illustration of the mode of action of the various pills : -Combined pills (estrogen and progestogen) : blocks ovulation by reducing production of LH and FSH, blocks adhesion of the egg by changing the thickness of the endometrium and blocks the progression of sperm by increasing the viscosity of cervical mucus. -Progestogen pill : the same mode of action except that they are less active in blocking ovulation. -The morning after pill : blocks ovulation by reducing production of LH and FSH blocks adhesion of the egg by changing the thickness of the endometrium.