What happens during an IVF egg collection

3 March 2025

Elysha Anderson

For those undergoing IVF, egg collection (or IVF egg retrieval) is a crucial step in the process. It marks the transition from ovarian stimulation to fertilisation and embryo development.

While the procedure is relatively short, it is highly structured and involves a team of specialists, including your consultant and embryologists, working together to maximise your chances of success.

We asked Elysha Anderson, Nursing Manager at The Evewell, to provide a step-by-step guide to what happens before, during, and after an IVF egg collection process.

Step 1: Ovarian stimulation and the trigger shot

Before the IVF egg collection process, the ovaries are stimulated with hormone injections to encourage multiple follicles (which contain eggs) to grow. This process usually lasts 10–14 days, during which you’ll have regular scans and blood tests to monitor follicle development.

Once the follicles have reached the right size, a trigger injection (usually hCG or a GnRH agonist) is administered. This injection is critical, as it mimics the body’s natural LH surge, prompting final egg maturation and ensuring they are ready for retrieval.

The timing is precise – egg collection is scheduled around 36 hours after the trigger shot to retrieve the eggs before ovulation occurs naturally.

Step 2: Preparing for IVF egg retrieval

On the day of the procedure, you will typically arrive at the clinic in the morning. The procedure is performed under sedation or light general anaesthetic (clinic-dependent), meaning you shouldn’t feel any discomfort during the retrieval. You’ll be asked to fast for a few hours beforehand, and you will be given information on what to expect post-procedure.

Meanwhile, the embryology team is preparing the lab, ensuring that the equipment and culture media are optimised for handling the eggs immediately once they are retrieved.

Step 3: The egg collection procedure

Once you are sedated and comfortable, the consultant will perform the IVF egg retrieval using a transvaginal ultrasound-guided aspiration technique:

1. A fine needle is inserted through the vaginal wall and into each follicle in the ovaries.
2. Gentle suction is applied to draw out the follicular fluid, which contains the eggs.
3. This process is repeated for each follicle, typically lasting 15–30 minutes.

The consultant works closely with the embryologists, who immediately examine the collected fluid under a microscope to identify and retrieve the eggs.

Step 4: What the embryologist does

Once the follicular fluid is extracted, the embryologists in the IVF lab carefully search for eggs. This is done using a high-powered microscope, as eggs are microscopic and invisible to the naked eye.

• Each egg is isolated and placed in a carefully controlled culture environment.
• The eggs are kept in incubators that closely mimic conditions inside the human body, maintaining optimal temperature and pH levels.

At this stage, the eggs are held in culture media until fertilisation occurs later in the day.

Step 5: Fertilisation and early embryo development

A few hours after retrieval, the eggs are fertilised with sperm. This can occur in two ways:

1. Conventional IVF – The eggs are placed in a dish with thousands of sperm, allowing fertilisation to happen naturally.
2. ICSI (Intracytoplasmic Sperm Injection) – A single sperm is injected directly into each mature egg, often used in cases of male factor infertility or previous failed fertilisation.

The embryologists closely monitor fertilisation over the next 16–18 hours. By the following morning, they check how many eggs have successfully fertilised and update the patient.

Step 6: Embryo monitoring over the following days

Once fertilisation occurs, the embryos are cultured in the lab for several days, typically up to day five (blastocyst stage). The embryology team carefully monitors the embryos’ growth, looking at key markers such as:

• Cell division rate – The speed and pattern of cell division indicate embryo health.
• Embryo grading – A scoring system is used to assess embryo quality.
• Development milestones – Checking if the embryo reaches the blastocyst stage, which has a higher chance of implantation.

Throughout this period, patients receive updates on embryo progress, and a decision is made regarding embryo transfer, freezing, or further testing, such as PGT-A (preimplantation genetic testing).

What happens next?

If the embryos reach the desired blastocyst stage and quality, the next step is to have a fresh embryo transfer, typically done on day five, in which the best embryo is placed into the uterus.

Any remaining embryos that meet quality criteria can be frozen for future attempts, providing additional chances for pregnancy.

Some patients won’t have a fresh embryo transfer, either due to family planning strategies, overstimulation or other medical reasons such as adding PGT-A to their treatment plan. Either way, you’ll know well ahead of your egg collection if you have a fresh or frozen transfer.

Recovery after egg collection

After the procedure, you’ll spend some time in the recovery room while the sedation wears off. Common post-retrieval symptoms include:

• Mild cramping or bloating
• Light spotting
• Fatigue and nausea due to anaesthesia

Most people return home the same day and are advised to rest. It’s essential to stay hydrated and monitor for any signs of ovarian hyperstimulation syndrome (OHSS), a possible side effect of ovarian stimulation. Contact your clinic for further advice if you are worried about any side effects or symptoms.

The IVF retrieval process

IVF egg retrieval is a key step in the IVF journey, requiring a carefully coordinated effort between consultants, embryologists, the nursing team and, of course, the patient.

Whether you’ve had collections before, are preparing for your first egg collection or considering IVF, knowing what happens behind the scenes can help you feel more informed and in control of your fertility journey.