IVF explained

IVF stands for In Vitro Fertilisation and it's a procedure that helps people who face challenges conceiving a baby to have a family.

The basics

When natural conception happens, the sperm fertilises the egg inside the woman's body. However in the IVF procedure, fertilisation of the egg with the sperm and the first few days of embryo development occur outside the body in a test-tube or a Petri dish, in controlled conditions in a laboratory. In Vitro is actually Latin and it means 'in glass' referring to the Petri dish where the sperm and egg are put together.

After fertilisation, early embryo development is checked in the laboratory by a scientist called an embryologist. When the embryo is 3 or 5 days old it is transferred into the uterus in the hope that the woman will become pregnant.

IVF is only one type of fertility treatment; however it is the most complex. Not all people who have fertility treatment require IVF, sometimes simpler treatments involving drugs, surgery or intrauterine insemination (IUI) can help.  Find out about other fertility treatments here.

Who uses IVF?

IVF is useful for people with fertility problems.  In heterosexual couples, about half of all fertility problems are male based and about half female based.

Sometimes men have little or no sperm, sometimes the sperm are blocked in the testes and sometimes there is poor sperm quality.  Occasionally, men may have frozen their sperm prior to treatment for cancer, as some treatments can cause infertility.

On the other hand some women suffer from endometriosis, their fallopian tubes may be damaged, or their ovaries may have stopped making eggs.  Occasionally, a woman may have frozen her eggs prior to treatment for cancer, as some treatments can cause infertility.

Sometimes doctors can't pinpoint the cause of fertility problems and this is called 'unexplained infertility', which affects around 30% of couples who struggle with infertility.

In cases where either the sperm or eggs are not available, donated sperm or eggs are needed.

Besides heterosexual couples there are other groups of people who turn to IVF to help them have a baby - lesbian couples and single women. These women need donated sperm, and may also have problems which intrauterine insemination won't overcome.

Sometimes it takes years of trying for a baby before people get help through IVF treatment and then it may take more than one IVF treatment before a woman gets pregnant. IVF treatment can be difficult to go through because it involves hormone drugs, and invasive procedures to collect the eggs, return the embryos and sometimes to retrieve the sperm.

Sometimes there is government funding available to help people who need IVF, but other times people need to pay for the treatment themselves.

Given all that, IVF-lings can probably understand just how much their parents wanted them!!!

Process of IVF and embryo development

STEP 1 – Ovulation Induction and Monitoring

Hormone drugs are given to the woman to increase the number of eggs developing in her ovaries. Fertility specialist doctors keep an eye on the eggs' development by using the results from blood tests and ultrasound scans. At the appropriate time, maturation of the eggs is triggered by another drug so the doctor can retrieve the woman's eggs at the right time. Usually the eggs will be used ‘fresh’, but sometimes eggs are frozen to be thawed and used later.

STEP 2 – Sperm Collection

A sperm sample (pictured right) is produced by the man and given to the laboratory. If a man doesn’t have any sperm in his semen, sperm can sometimes be surgically retrieved.  Sometimes the sperm will be used ‘fresh’, and sometimes it will be frozen to be thawed and used later.

STEP 3 – Egg Collection

The doctor uses an ultrasound scan and a long needle to collect eggs from the ovaries. This procedure takes about 15 minutes and pain relief is used to help with any discomfort.

STEP 4 - Fertilisation

The embryologist takes the eggs and sperm and places them into a solution containing nutrients in a Petri dish, which is placed in an incubator. If / when a sperm joins the egg, fertilisation has occurred.

STEP 5 – Embryo Development

All going well an embryo will develop. This is a pronuclear embryo that is 1 day old (pictured below left). Embryos are then cultured for a further 1-5 days. During this time a series of checks helps identify the embryo(s) with the greatest developmental potential. Embryos may be left to develop or frozen to be thawed and used later.

Below middle is pictured a two cell embryo that is 1-2 days old .

1 Cell Embryo  2 Cell Embryo  8 Cell Embryo

STEP 6 – Embryo Replacement

The embryo continues to develop into an eight cell embryo (pictured above right) at 3 days old. This is a normal pace of development, and sometimes embryos are replaced back into the uterus on this day.

By 4 days the embryo forms a morula (pictured below left) which means Mulberry in Latin - simply because it looks like a berry.

By day 5 the embryo has developed into a blastocyst (pictured below middle). Nowadays, it is increasingly common to replace blastocysts into the uterus. Usually one or, if the woman is older, sometimes two embryos are selected for transfer back into the uterus. In the past, two or three embryos were replaced at the same time to increase the chance of pregnancy. That also increases the chance of twins and even triplets. That is why so many IVF-lings from earlier years are twins.

Morula - 4 day old Embryo  Blastocyst  A Embryo 'hatching'

STEP 7 - Pregnancy

By day 6 the embryo is in the uterus and it will ‘hatch’ (pictured above right) - which literally means it will pop out of its shell. It needs to do this in order to implant in the uterus.

14 days after the original egg collection the woman has a blood test to check for signs of pregnancy.


ICSI stands for intracytoplasmic sperm injection and is a variation of IVF that is used if a man has very few sperm.

Instead of the sperm and eggs being mixed in a Petri dish, a single sperm is injected into the mature egg.  ICSI allows almost any man with any sperm, either in his semen or in his testes, to try IVF.

Limitations of IVF

The limitations that apply to natural fertility also apply to IVF treatment. Although IVF can give older women a better chance of getting pregnant than natural fertility, it does not overcome the fall in fertility that is seen when women usually reach their late 30’s and early 40’s - if a woman’s eggs are of poor quality or there are none left, the only option will be to use donor eggs.

Success with IVF also relies on a woman responding to the drugs. If she does not respond, the ovaries will only produce one egg as usual, which greatly reduces the chance of success.

Generally, IVF will not be useful if a woman has suffered from repeated miscarriages.

Success with IVF Treatment

Nowadays the success rate for IVF is approximately 45% per cycle of treatment for women aged 35 and under.   This decreases to approximately 20% with women aged 40, and less than 10% with women aged over 42. You can read more about the success rates of IVF and other fertility treatments on the Fertility Associates website here.

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