The menstrual cycle can be described by the ovarian or uterine cycle. The ovarian cycle describes changes that occur in the follicles of the ovary whereas the uterine cycle describes changes in the endometrial lining of the uterus. Both cycles can be divided into three phases. The ovarian cycle consists of the follicular phase, ovulation, and the luteal phase, whereas the uterine cycle consists of menstruation, proliferative phase, and secretory phase. These cycles do not occur during pregnancy as the fertilization results in the formation of the zygote and it attaches itself on the wall of the uterus.
So the correct option is 'the ovarian and uterine cycles do not occur'.