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The biology of creating a baby is an amazing process and here we take you all the way through the conception journey and offer advice on how to make sure your body is in the best condition to conceive.

The reproductive system in women

The female reproductive organs comprise external and internal organs. The external organs are the vaginal entrance, the urethral opening (tube from the bladder through which you pass urine), the labia or vaginal lips and the clitoris (highly sensitive erectile tissue).

The internal organs comprise:

  • The vagina - a muscular tube connecting the cervix to the opening at the external genitals
  • The cervix - the lower part of the uterus. The cervical canal, which connects the uterus to the vagina, produces cervical secretions
  • The uterus (womb) with the uterine lining or endometrium which is shed on a cyclical basis (the period)
  • Fallopian tubes - fine tubes linking the ovaries to the uterus
  • Ovaries - with follicles containing eggs. Ovaries also produce the female hormones oestrogen and progesterone

An egg is released at ovulation on a roughly monthly basis. The egg travels along the fallopian tube towards the uterus. If sperm are present in the fallopian tube and the egg is fertilised, this then continues along the tube and embeds in the lining of the uterus (endometrium). This is implantation and conception has now occurred. The uterus acts as a home for the developing embryo.

The menstrual cycle

A woman is born with her lifetime supply of eggs, all stored in her ovaries which are each around the size of a small plum. Each month an egg grows and is released from one ovary ready for fertilization and the lining of the uterus prepares for a possible pregnancy. If fertilization does not occur, a period (shedding of the lining) will occur within 14 days of ovulation. This process is known as the ‘menstrual cycle’.

An average menstrual cycle is 28 days in length and comprises two phases: the follicular phase (from the start of the period until ovulation) and the luteal phase (from ovulation to the next period). The menstrual cycle involves a complex interplay of hormones within a women’s body which are released by the brain at specific stages.

(click image to expand)

Follicular phase: Approximately days 1-14 of the cycle

This phase is the first half of the cycle – it starts on the first day of a woman’s period and ends on the day of ovulation.

The menstrual cycle starts on the first day of bleeding. The hypothalamus in the brain releases gonadotrophin-releasing hormone which tells the pituitary gland to release follicle-stimulating hormone (FSH). The FSH stimulates about 20 eggs to start developing within sacs known as follicles.

As the eggs develop, the growing follicles release estrogen which reduces FSH production so that only one egg continues to grow – this is the dominant follicle. Estrogen also tells the lining of the uterus to thicken up and prepare for implantation of a fertilized egg.

The estrogen levels in the body continue to rise until it triggers a surge of luteinizing hormone (LH) from the pituitary gland which in turn ruptures the dominant follicle and the egg is released on to the outside of the ovary – ovulation has occurred.

Luteal phase: Approximately days 15 – 28 of the cycle

The second half of the cycle – it starts at ovulation and ends at the next period.

Once the egg has been released, the ruptured follicle continues to receive pulses of LH which helps it turn into a small cyst called the ‘corpus luteum’ (or yellow body) which in turn starts to produce progesterone. This hormone encourages the womb lining to thicken further and the cervix to close.

If at this stage the egg has not been fertilised, progesterone levels drop and the womb lining sheds, passing through the body as a period 10-16 days later.

Progesterone levels will continue to drop and the brain releases FSH, starting the whole cycle again. If fertilisation does occur then the fertilised egg travels down the fallopian tube into the uterus and implants – pregnancy begins.

The reproductive system in men

Male reproductive organs comprise the penis and the scrotum, which contains the two testicles that are responsible for creating sperm. Some 100 million sperm are made in each testicle every day. Sperm production is controlled by the hypothalamus and the pituitary gland in the brain (as for women). The pituitary gland produces the hormones FSH (Follicle stimulating hormone) and LH (Luteinising hormone). They begin to act on the testicles, encouraging production of testosterone and sperm. In men the production of these hormones should be constant, giving a continuous supply of sperm.

When a sperm matures it moves to a tube on top of each testicle called the epididymis. Here it is stored before moving to another tube called the Vas deferens, connecting the epididymis to the ejaculatory duct. It takes approximately 64 days for an immature sperm cell to develop into a mature sperm, and another 10-14 days to pass through the epididymis ready for ejaculation. Sperm are stored in the epididymis waiting for ejaculation and when this occurs during sexual intercourse, the sperm are released into the woman’s vagina and begin the journey through the female reproductive organs. Each ejaculation will release an average of 200 million sperm.

Sperm structure

The sperm is comprised of 3 main sections: The head, the mid-piece and the tail.

The head of the sperm consists of 2 parts, the acrosome and the nucleus. The acrosome contains enzymes that enable the sperm to penetrate the egg, and the nucleus contains the 23 chromosomes which make up the fathers genetic contribution to the child.

The mid–piece contains the mitochondria, this is the energy supply for the tail.

The tail is long, slender and it whips back and forth energetically to propel the sperm through its journey.

Post ejaculation

After ejaculation, the sperm begin their journey through the female reproductive system. The sperm must move through the semen inside the vagina towards the cervix. Depending on the stage of the menstrual cycle, the sperm’s journey could end here as the secretions act as a cervical plug preventing sperm penetration for a large part of the menstrual cycle. If the timing is right, the sperm will be able to pass through the cervical secretions and into the womb. This can only happen if the secretions are of a thin, watery consistency with an alkaline pH level. Only about 0.1% of sperm will make it to this stage.

Once they arrive in the womb, the sperm must navigate into the fallopian tubes. Most sperm will become lost in the complex glands lining the cervical canal or the wall of the womb on their way. A very small number of sperm will make it all the way to the fallopian tubes, usually around 100 or so. The sperm can reach their destination in just a few minutes, but they can live there and remain healthy for several days (even up to a week in extreme circumstances).


Any sperm alive in the fallopian tubes can then meet and bind with an egg after it has been released from one of the ovaries. When a sperm attaches to the surface of the egg, the acrosome cap release substances that dissolve a hole in the egg coat allowing the sperm head to penetrate the egg and deposit the males DNA (chromosomes) into the nucleus of the egg. This is the fertilisation stage.

Sperm quality

Poor sperm quality is one of the most important factors in fertility and almost 50% of cases of infertility are down to a male factor, which tends to surprise a lot of people. Sperm need to be produced in sufficient numbers and quality in order to reach and penetrate the egg. Evidence has shown that diet and stress can have an effect on the quality of sperm.

Zita West’s tips to boost sperm quality:

- Eat a good breakfast everyday as it provides energy. Without a good breakfast, the body goes into survival mode and the production of sperm decreases.

- A man must ejaculate regularly, even when you’re not having sex. Sperm don’t live forever; if they’re not ejaculated regularly they will overheat and may die off in the epididymis. Long durations without ejaculation means the amount of dead sperm builds up and as they decay they release toxins that harm the fresh sperm.

The fertile time

Working out your fertile time can be hugely beneficial when trying to conceive. It’s the time when the egg is going to be released from one of the ovaries and the time when sperm are most likely to reach the uterus. During the fertile time a woman’s cervix opens and her secretions become moist, white and sticky and then wetter, clear and stretchy. These secretions nourish the sperm and encourage its progression through the cervix and into the uterus.

The fertile time will not always be the same length and the day that the egg is released cannot be exactly determined. That is why it’s important to have regular sex to ensure that fresh sperm are always present in the uterus and fallopian tubes.

There’s a simple way to get a rough idea of your fertile time if you know the length of your cycles from the past 6 to 12 months….

  • Simply write down all of the lengths of your previous cycles.
  • Then subtract 20 from the lowest number, and subtract 10 from the highest.
  • This gives you an estimated start and end date for your fertile time.
  • For example, if your last 6 cycles have been 28, 29, 27, 29, 26, 30 days long, then 26 is your shortest cycle (lowest number), so subtract 20 which gives you 6, meaning your fertile time starts around the 6th day of your cycle. Then subtract 10 from your longest cycle (highest number) which in this case is 30. This gives you 20, meaning your fertile time ends around the 20th day of your cycle.

There are other ways to find out your fertile time such as by using our Ovulation calculator which pinpoints the two most likely days for ovulation.

Conception timeline
Time period What happens?
Day 1-6: (Period)
  • The womb lining from the previous cycle is shed and exits the body as a period.
  • Follicles begin to develop in the ovaries.
  • FSH is released into the bloodstream to stimulate follicle growth.
Day 7-9 (Relatively infertile time)
  • The vagina will feel dry as the cervix is tightly closed with thick secretions preventing sperm from getting through.
  • One of the follicles will grow faster than the others in a natural cycle to become the dominant one.
  • Estrogen levels begin to rise.
Day 10-18 (Fertile time)
  • This is the best time to have lots of sex as the sperm will be greeted by wetter, clearer and often stretchier secretions which nourish the sperm and encourage it to swim upwards. Sperm can survive for an average of 2-3 days and up to 7 days in this environment.
  • Estrogen levels continue to rise.
  • FSH production is shut down and a surge of LH is released, triggering ovulation.
  • The dominant follicle becomes the corpus luteum and progesterone is released.
  • Any strong sperm should be waiting in the fallopian tubes ready to fertilise the egg
  • The non-dominant follicles will decrease in size and degenerate in a natural cycle.
  • Ovulation occurs
Day 19-28 (Infertile time)
  • The waiting sperm will meet the egg in the fallopian tube and, hopefully, penetrate and fertilise it.
  • The corpus luteum will produce progesterone which encourages the womb lining to thicken, closes the cervix and thickens the secretions to prevent any further sperm getting through.
  • If the egg is not fertilised, progesterone levels will drop and the womb lining begins to shed, starting the cycle again.
  • If the egg has been fertilised then it travels down one of the fallopian tubes into the uterus and implants itself – pregnancy has begun!
Getting your body ready for conception

Fertility involves the whole body, so it’s important to try and stay healthy inside and out. Many lifestyle choices can have an effect on your chances of conception and we’ve looked at these further below:


When it comes to fertility, an unbalanced lifestyle of work and personal time can cause problems. Not only does it make things difficult to plan but it can also cause stress, especially when combined with the emotional strain of trying for a baby. Stress levels can increase the levels of other hormones in the body such as cortisol, which interferes with the reproductive hormones. Another is prolactin which can suppress ovulation and reduce a woman’s libido. This is the same for men; stress can cause irregularities in hormone levels which can lead to a lower sperm count. It’s a good idea to slow your lifestyle down, remove any pressure from work and enjoy yourself by doing things you like to do. Click here to find out more about the impact of stress on fertility.


For men and women, being overweight and having a BMI (Body Mass Index) over 25 can have an impact on the ability to conceive.

For women it can interrupt normal menstrual cycles and stop ovulation. When a woman is overweight fat cells store excess estrogen and this causes hormonal imbalances that interfere with ovulation. Being overweight can also increase the chances of a miscarriage and the need for a caesarean section. Plus it also has an effect on pregnancy as it can cause health issues such as high blood pressure and diabetes. For men, excess pounds can affect male reproduction because of a process carried out in fat cells called aromatisation, which converts testosterone (the male hormone) to estrogen (the female hormone) thus reducing sperm count.

Being underweight can also negatively impact fertility as the body senses famine and shuts the reproductive system down. Women that are underweight may not have enough estrogen in the body for ovulation to occur.


It is important to maintain a healthy level of exercise as it can reduce stress, regulate your blood sugar, promotes good circulation to the reproductive organs and also lifts your mood.

When trying for a baby it can be difficult to know how much exercise is right but the safe limit is around 30 minutes a day. If you’re overweight then you will need to increase the amount of exercise in order to reduce your body fat levels to a normal range. If you currently do no exercise then try to build up to 30 minutes a day.

Men who do too much exercise could be impairing their fertility. Over exercising can divert testosterone away from your reproductive organs and lower sperm count.

Caffeine & alcohol

Caffeine and alcohol are common stumbling blocks for couples trying to conceive. It should be a joint effort to cut down on your intake as caffeine can affect your chances of conception. The maximum recommended daily intake is 200mg caffeine when planning pregnancy and during pregnancy, which means no more than 2 mugs of instant coffee, or 1 mug of filter coffee, or 2 mugs of tea, or 5 cans of cola, or 2 cans of energy drinks, or 4 bars of chocolate per day. Caffeine is an energy and mood booster and if you suddenly cut it out of your diet then you could suffer withdrawal symptoms such as headaches, nausea, irritability and fatigue. It’s advised to cut down to just the odd cup of coffee every now or switch to decaffeinated or herbal options.

Although it is unclear what effect alcohol has on conception, it does have an effect on pregnancy and can cause serious abnormalities for an unborn child. If you do drink, avoid getting drunk, and try to limit alcohol to the occasional drink (no more than 6 units a week when trying to conceive). It is advised that you don’t drink after conceiving particularly for the first 12 weeks of pregnancy.


Smoking is a big factor when it comes to infertility as it can cause harm to the ovaries and accelerate the loss of eggs. It can also bring menopause forward by several years and interfere with estrogen levels. For men, smoking can seriously impact sperm count and quality; it impairs sperm shape and function. Quitting smoking is a must in order to aid fertility.

Medical information provided by Zita West, Midwife, Fertility and Pregnancy Expert.

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