Once the ovum is fertilised, the corpus luteum continues releasing progesterone to facilitate
implantation of the egg in the uterus
An increase in the amount of progesterone helps facilitate the implantation of a fertilised egg in the uterus, as well as helps maintain pregnancy by preventing menstruation. The progesterone can cause many side effects including stomach upset, changes in appetite, weight gain, fluid retention and swelling, fatigue, acne, drowsiness or insomnia.