Fertility and Getting Pregnant

Getting pregnant involves a number of complex stages. Each of these stages must be successfully completed before a positive pregnancy test can be achieved.

In a normal menstrual cycle, a woman usually produces a single egg grown in a fluid filled sac known as a follicle. This process starts at the beginning of each menstrual cycle, day 1 being the first day. Between day 2 and day 6, a hormone known as Follicle Stimulating Hormone (FSH) is produced. This triggers a number of follicles to develop in the ovary. Only one of these follicles will produce a mature egg which will become a dominant follicle, the others will stop growing.

As the dominant follicle continues to grow, it starts to release another hormone, Oestrogen. Oestrogen also helps the lining of the uterus, known as the endometrium, to thicken.

When the Oestrogen has reached a certain level, the FSH levels reduce. Another hormone known as Luteinizing Hormone (LH) is produced. LH matures the egg in the follicle and the now mature egg is released from the follicle 24-36 hours after the highest LH peak.

Dominant Follicle

The egg then passes into the fallopian tube. The follicle that has ruptured, releasing the egg, is now referred to as the Corpus Luteum (CL). The Corpus Luteum continues to produce Oestrogen, but in addition also produces another hormone known as Progesterone. Progesterone enables the endometrium to further thicken. This is important to form a receptive environment for the later embryo to implant. The released egg is viable for fertilisation to occur within the fallopian tube for a limited period of time, approximately 12-24 hours. This is around day 14 of the menstrual cycle.

Unfertilised Egg

It is here in the fallopian tube that fertilisation will occur if sperm is present. If fertilisation has not occurred the corpus Luteum stops producing Progesterone, and the endometrium will start to shed around day 28. The woman will then have a menstrual bleed.

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