In vitro fertilization (IVF) literally means, ‘fertilized in glass’.

Very simply, eggs are removed from the ovary just before ovulation. The eggs and sperm are then placed together outside the body in a specialised laboratory environment in a glass dish or test-tube. If fertilization and normal embryo development occurs, the best embryo(s) is (are) returned to the uterus (womb) 2-5 days later.  The original indication for IVF was damaged fallopian tubes, but it is now also used for a wide range of disorders such as unexplained infertility, endometriosis and male factor infertility (ICSI).

Stages of an IVF Cycle

Superovulation > Ultrasound Monitoring > Egg Collection > Fertilization > Embryo Transfer


The chances of pregnancy with IVF are increased if more than one egg is recovered. To achieve this, the ovaries are stimulated with fertility drugs (super-ovulation) with the intention of growing at least three mature eggs. A number of different drugs and protocols are used in the treatment.

The most commonly used protocol for IVF involves first giving a drug called a gonadotropin releasing hormone agonist (GnRH agonist) either by daily injection or as a nasal spray. The aim of this drug is to temporarily suppress the woman’s natural hormones and control the timing of ovulation. This is called down-regulation and allows for greater control over the treatment cycle.

After ‘down regulation’ has been achieved (approx. two weeks), the GnRH agonist is continued, and injections of FSH ± LH are given to stimulate the ovaries.  The second protocol we use is called an Antagonist Protocol where an additional injection is introduced on day 5 or 6 of stimulation to again allow good control of the woman’s hormones.

Ultrasound Monitoring

Eggs are microscopic but they grow in fluid filled structures (follicles) which can be clearly seen on ultrasound scan. The development of the follicles is routinely monitored using vaginal ultrasound scans. After about 7-12 days of the injections, the follicles will almost be mature. The woman is asked to stop her stimulation drugs and a trigger injection called human chorionic gonadotropin (hCG) is given. The hCG injection is carefully timed and is usually given at night with the egg collection being performed 36 hours later in the morning.

Egg Collection

This is a minor surgical procedure, carried out @ Merrion Fertility Clinic procedure rooms using ultrasound guidance and an Anaesthetist providing excellent intravenous pain relief and sedation.

A vaginal ultrasound probe with a fine hollow needle attached to it is inserted into the vagina. Under ultrasound guidance, the needle is then advanced into the ovary to suck out the fluid from the follicle that contains the egg. Each follicle is emptied in turn and the fluid passed directly to the laboratory team. The eggs are identified and prepared for interaction with partners sperm. The whole procedure takes about 20-30 minutes.



On the day of egg collection, the male partner is asked to provide a semen sample. The sperm is washed in culture medium and prepared. The eggs are collected into a specially prepared culture medium and once collected, they are examined under the microscope. The eggs are then placed in the incubator for a period of time (about 3-4 hours) before they are mixed with the selected sperm.

Between 50,000-100,000 sperm are mixed with each egg in a drop of specially prepared culture medium. This medium is prepared in a labelled dish that is kept in the incubator to allow fertilization to occur. It takes about 18 hours for the egg to be fertilized. Usually about 60-70% of the eggs collected will be fertilized, but this can vary from 0% to 100%. Regrettably, some 3% of couples will not achieve fertilization of any eggs.

About 12 hours later the fertilized egg starts to divide into two cells, and subsequently into four and so on. After about 48-72 hours from the egg collection, the embryos will usually consist of 4-8 cells each, by five days from the egg collection they will have formed blastocysts. Embryos or blastocysts are ready for transfer to the woman’s uterus on day 2 or day 3 (embryos) or day 5 (blastocysts).

Embryo Transfer


The embryo transfer procedure is quite simple and is usually pain free. No anaesthetic is necessary. One or two embryos suspended in a drop of culture medium are loaded in a fine plastic catheter with a syringe on one end. Gently and carefully, the doctor or nurse guides the tip of the catheter through the vagina and cervix, and deposits the embryos into the uterine cavity. The procedure is guided using ultrasound scanning to check the position of the catheter.

Once the embryos have been replaced, the woman rests for a short while before going home. There is no chance of the embryos ‘falling out’ and women are advised to return to their normal routine as soon as possible.

The number of embryos to be replaced will depend upon several factors such as female age, previous pregnancies and number of cycles. It is well proven worldwide that the safest pregnancy, for both the mother and child, is a singleton pregnancy. Twin pregnancies are at an increased risk of miscarriage, premature delivery, fetal or neonatal death and cerebral palsy. This risk increases dramatically for triplets, quadruplets etc. Our policy is to transfer one or two embryos under normal circumstances. This will be discussed in detail with every couple prior to treatment and again on the day of embryo transfer.