Conception is a process that begins with fertilisation and ends with implantation. For fertilisation to take place an egg needs to meet a sperm – usually through a man and woman having sex.


  • When the ovary releases the egg, it is picked up by the fallopian tube where it can be fertilised by the sperm. Sperm are able to wait around in the uterus and fallopian tube until the egg is released.
  • Small beating hairs and tiny wave-like contractions help the egg travel along the fallopian tube where it may meet a sperm within minutes or hours of being released from one of the ovaries. The egg only lives for up to 24 hours so it increases the chance of pregnancy if the sperm are ready and waiting. If you have sex 2–3 times a week you will help ensure there is always sperm waiting.
  • Only a smaller number of sperm will actually survive the trip to the fallopian tubes and finally only one sperm will actually enter the egg.
  • The sperm attaches itself to the egg and produces a special substance which dissolves the outer coat of the egg. Once it has entered, a quick repair of the egg coating means that no other sperm can get in.
  • Once the sperm is fully inside the egg, fertilisation has taken place.
  • The fertilised egg is wafted down the fallopian tube to the ready-prepared uterus. Here, it settles and over a few days attaches itself to the thick, nutritious lining. Implantation has now taken place, conception is complete and the pregnancy begins. The time from ovulation to implantation is around ten days.
  • Once the pregnancy has begun, the pregnancy hormone human chorionic gonadotrophin (hCG) begins to be produced.

Sometimes a pregnancy develops outside the uterus, usually in the fallopian tube. This is called an ectopic pregnancy.

Conception – did you know?

  • Conception is a process that starts with fertilisation and ends with implantation.
  • It takes about three hours for the sperm to fully enter the egg.
  • The egg can be fertilised by sperm that have been ejaculated up to seven days before.
  • The egg has special places on the outside coat that attract the sperm.
  • It takes a couple an average of 3–6 months to conceive, if they are having sex frequently (2–3 times per week) during their fertile time.
  • Women over 30 years old may take longer to conceive.
  • Women who are either very underweight or very overweight may have more difficulties conceiving.
  • An average pregnancy lasts 280 days.


The pregnancy test

The earliest and most reliable sign of pregnancy for women with a regular menstrual cycle is a missed period. Sometimes women who are pregnant have a shorter or lighter period than normal.

A woman can carry out a pregnancy test from the first day of a missed period. Some tests suggest that pregnancy tests can be carried out earlier than this, but the effectiveness of this varies. For women who don’t have regular periods, the earliest time to do a test is 21 days from the last time that they had unprotected sex. For some women the test does not show positive until their period is at least a week late.

Pregnancy tests look for the pregnancy hormone hCG, which is found in the urine of pregnant women. A positive test is almost always correct. But women can sometimes get a negative result if the test is carried out too early or not correctly, even though they may be pregnant.

It’s all in the genes

How a baby looks is determined by the genes it inherits from its parents. Genes are contained in chromosomes – tiny thread like structures – and each chromosome contains thousands of genes. It is these genes that determine your height, build, blood group, and eye and hair colour. Some characteristics will be inherited from the mother and some from the father.

So how is the sex of the baby decided?

An egg has 22 chromosomes and one sex chromosome known as the X chromosome. A sperm also has 22 chromosomes and one sex chromosome which can either be an X or a Y chromosome. It is the sperm’s chromosome that determines the sex of the baby. A simple way to look at it is like this:

  • If the egg is fertilised by a sperm containing an X chromosome the baby will be female. Mother X + Father X = XX = Female.
  • If the sperm contains a Y chromosome the baby will be male. Mother X + Father Y = XY = Male.

To date, there is no reliable scientific evidence to support claims made for choosing the sex of the baby, such as when you have sex, sexual positions or diet.

Making sense of contraception and sexual health

Understanding how your body works can help you and your partner to plan a pregnancy or to avoid one. There are many different methods of contraception which suit people at different times of their lives. They all work in different ways, either by preventing or affecting ovulation, stopping fertilisation by preventing the sperm from meeting the egg, or by identifying the fertile and infertile times of the menstrual cycle.

Emergency contraception

If you have had sex without using contraception or think your method might have failed there are two emergency methods you can use.

  • The emergency hormonal pill – must be taken up to three days (72 hours) after sex. It is more effective the earlier it is taken after sex.
  • An IUD – must be fitted up to five days after sex, or up to five days after the earliest time you could have released an egg (ovulation).

Ask your doctor or nurse about getting emergency pills in advance, just in case you need them.

Sexually transmitted infections

Most methods of contraception do not protect you from sexually transmitted infections.

Male and female condoms, when used correctly and consistently, can help protect against sexually transmitted infections. Diaphragms and caps may also protect against some sexually transmitted infections. If you can, avoid using condoms containing Nonoxinol 9 (spermicidally lubricated), as this does not protect against HIV and may even increase the risk of infection.