The female reproductive system and menstrual cycle are key factors in female fertility. In order to become pregnant a women needs to

• Menstruate regularly
• Produce a mature egg each menstrual cycle
• Produce oestrogen and progesterone
• Ovulate
• Have no blockages in the fallopian tubes
• Have receptive endometrial lining for implantation

The menstrual cycle

The menstrual cycle refers to the maturation and release of an egg and to the preparation of the uterus to receive and nurture an embryo. The cycle is usually 28 to 32 days in duration and has three phases:

Phases of the menstrual cycle:

Follicular Phase - Day 1 of the cycle is the first day of menstruation (where the uterus sheds its lining from the previous cycle). The pituitary gland releases two hormones – Follicle Stimulating Hormone (FSH) and Luteinising Hormone (LH) which stimulate the ovaries to produce follicles. Usually one follicle will become the dominant follicle and go on to produce an egg. The developing follicle releases oestrogen which changes the cervical mucus mid cycle ensuring it is receptive to sperm.

Ovulatory Phase – Ovulation occurs with the LH surge. It is this surge which triggers follicle rupture and release of the egg. This usually occurs 14 days prior to the onset of menstruation. 

Luteal Phase – The follicle which produced the egg becomes a functioning gland called the corpus luteum. This gland produces oestrogen and progesterone, which are necessary for maturing and nourishing the endometrium, to ensure that a fertilised egg may implant and develop into a pregnancy. If the egg is not fertilised within about a day of ovulation, it will die and be absorbed by the woman's body. If implantation does not occur within approximately two weeks, the corpus luteum will die, causing sharp drops in levels of both progesterone and oestrogen. These hormone drops cause the uterus to shed its lining.