The secretory phase is the final phase of the uterine cycle and it corresponds to the luteal phase of the ovarian cycle. During the secretory phase, the corpus luteum produces progesterone, which plays a vital role in making the endometrium receptive to the implantation of a blastocyst (a fertilized egg, which has begun to grow). Glycogen, lipids, and proteins are secreted into the uterus and the cervical mucus thickens. In early pregnancy progesterone also increases blood flow and reduces the contractility of the smooth muscle in the uterus and raises the woman's basal body temperature.