The Effect of Hormones in Fertility and Pregnancy

September 5 2014 8:22am

Many complex processes occur within the body. In order to control these processes, different parts of the body need to communicate with each other. Hormones are a group of chemicals  that are involved with internal communication. They are transported via the blood which grants them access to every part of the body. This is why one hormone can have so many varying effects.


Oestrogen and Progesterone Govern the Menstrual Cycle

 In women, the two main hormones in fertility are Oestrogen and Progesterone. Both are produced within the ovaries. These two hormones govern the menstrual cycle. The menstrual cycle is divided into two phases:

1. The Follicular Phase (governed by Oestrogen).

2. The Luteal Phase (governed by Progesterone).

The names of these phases are given by the state of the shell that encases and protects the ovum (egg cell). ‘Follicular’ refers to the shell that surrounds the ovum. When encased by the shell, the entire unit is known as a follicle. In this state, oestrogen is produced by the follicle. When the egg is ejected (just before fertilisation), the collapsed shell is known as the corpus luteum. It is at this point that the second phase begins. Now the corpus luteum will secrete progesterone until either the egg is implanted or menstruation occurs.


Hormones After Implantation

Once implanted, the child must make its presence known, biologically, to the mother. This is achieved via the hormone, hCG (human Chorionic Gonadotrophin). hCG is released on the 6th day by the fertilised egg. It increases kidney function to eliminate biological waste more efficiently. However, this means that urination is more frequent. hCG, interestingly, is also the first major chemical confirmation that pregnancy has begun. It is used in pregnancy tests as some of it will drain into the bladder.

Oestrogen and Progesterone maintain their importance even after implantation, however they are now also created by the placenta. The placenta is formed about four weeks into pregnancy, around the same time that the highly coveted “baby bump” makes an appearance. Half of the developing cells are recruited by the body to become the placenta, the go between for the parent and the child. As mentioned earlier, hormones can have a multitude of effects in the body due to their ability to access every part of the body via the blood. Although their primary roles are fundamental to the development and health of the baby, the side effects can be unpleasant.


 Effects of Oestrogen and Progesterone


– Increased blood circulation. Can cause sinus congestion, headaches and reddening of the skin.

– Increased breast development and milk production.

– Bone development in limbs of the baby.

– Organ development in the baby.


– Maintains placenta function

– Maintenance of uterine wall.

– Softening of the cartilage and relaxing of smooth muscle (aided by the hormone, Relaxin)

Smooth muscle is any muscle tissue under subconscious control, unlike skeletal muscle (such as those in our limbs that allow us to move). Smooth muscle is found in organs and helps maintain chemical function in the body. When Progesterone and Relaxin cause the relaxation of smooth muscle and cartilage, this can have quite a ranged effect on the body. The purpose of this is so the baby has more room to grow but the side effects can include, heartburn, constipation, bloating, bleeding and swelling gums, acne and increased sweating.

Oestrogen’s role in increasing blood circulation can also have adverse effects (usually vague properties end up causing more unwanted side effects). Skin can turn red and blotchy due to the overuse of capillaries near the skin surface. Increased circulation of this nature can also lead to headaches and congestion of the sinus.

A baby’s development causes great hormonal changes in the mother right through to childbirth and breastfeeding but (most!) new parents have no doubt that the reward is well worth the trouble.

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