Egg Collection: What Actually Happens on the Day

The honest picture, with numbers

Egg collection is the only surgical step in a standard IVF cycle, and it is short. The NHS puts it at around 20 minutes; the HFEA says about half an hour. A fine needle is passed through the vaginal wall into each ovary under ultrasound guidance, the fluid inside each follicle is drawn off, and it goes straight to the embryology laboratory next door.

For a sense of how routine this is: the HFEA reports that around 53,000 patients had IVF at licensed UK clinics in 2024, across more than 100,000 treatment and storage cycles. Egg collection is one of the most frequently performed procedures in British reproductive medicine.

The number that dominates the day is how many eggs come out, and it helps to understand what that number is before you are lying on the table. Follicles are not eggs. A scan counts follicles; the collection finds out how many of them held a mature egg. The two numbers often do not match, and that is not a mistake by anyone.

Sedation, pain, and what NICE actually says

Conscious sedation is the recommended default

NG257 recommendation 1.47.1 tells clinics to offer conscious sedation for transvaginal retrieval of oocytes, describing it as a safe and acceptable method of providing analgesia. The NHS describes being offered medicine that makes you sleepy; the HFEA says collection is done under sedation or general anaesthetic. You are not expected to get through this unmedicated, and if that is what is being suggested, it is a conversation to have well before the day rather than on it.

Follicle flushing: ask whether it is planned

NG257 recommendation 1.47.2 tells clinics not to offer follicle flushing before oocyte retrieval where there are at least 3 follicles, because it does not increase the number of oocytes retrieved or pregnancy rates, and it increases both the duration of the procedure and the associated pain. That is an unusually blunt recommendation: it names a technique, says it does not work, and says it hurts more. If flushing appears on your plan, ask which half of that sentence your clinic disagrees with.

The hours afterwards

The HFEA says you may feel a little sore or bruised. RCOG's guidance on the abdominal discomfort that follows stimulation is specific: paracetamol or codeine are appropriate, and anti-inflammatory painkillers such as aspirin and ibuprofen should be avoided because they can affect the kidneys. It also advises staying reasonably active rather than lying still, to reduce the risk of a clot. That advice is written for ovarian hyperstimulation syndrome, but it is why clinics steer you away from ibuprofen in this window generally.

What happens to the eggs, and when you hear

While your eggs are being collected, a sperm sample is produced in a private room at the clinic, or donor sperm is brought out of storage. The NHS states that the clinic will call you the next day to tell you how many embryos have been created and how many they might be able to use.

That call is the first real attrition point of the cycle, and it is usually where the plan first changes. Not every follicle yields an egg, not every egg is mature, not every mature egg fertilises, and not every fertilised egg keeps dividing. None of those steps is a moral test. They are the reason clinics talk about cohorts rather than single embryos.

When a cycle stops here

The HFEA sets out the reasons treatment is cancelled at or around this point: the ovaries do not respond to the stimulation drugs; the ovaries over-respond and hyperstimulation becomes the greater risk; no eggs are found because the follicles that developed turn out to be empty; the eggs collected do not fertilise; or the embryos fail to develop in the laboratory so none can be transferred.

NG257 asks healthcare providers to define a cancelled IVF cycle as one where an egg collection procedure is not undertaken, and to take cancelled cycles due to low ovarian response into account when considering whether further IVF is suitable. That definition is not academic. Whether a funded cycle counts as used can hinge on which side of egg collection the cancellation fell.

The week after: the hyperstimulation window

Ovarian hyperstimulation syndrome is the risk specifically attached to this stage. The HFEA states that patients who develop strong OHSS symptoms generally do so in the week after egg collection, and that around a third of women have mild OHSS, usually manageable at home with pain relief. RCOG puts mild OHSS at as many as 33 in 100 women having IVF, with just over 1 in 100 developing moderate or severe OHSS, and notes the risk is higher if you have polycystic ovaries, are under 30, have had OHSS before, or conceive in the same cycle. NG257 requires clinics providing gonadotrophin stimulation to have protocols for preventing, diagnosing and managing it.

The distinction that matters is direction of travel. Ordinary post-collection soreness plateaus and then settles. Hyperstimulation builds.

What to do next

1. Ask what sedation you are being offered, who administers it, and whether an anaesthetist is present. NG257 sets conscious sedation as the recommended standard.
2. Ask whether follicle flushing is planned and, if it is, on what grounds, given recommendation 1.47.2.
3. Get the cancellation policy in writing before you start, including what happens to your funded or paid cycle if collection does not go ahead.
4. Arrange an escort home and clear the next day. Sedation rules out driving, and the fertilisation call comes the following morning.
5. Save the clinic's 24-hour number in your phone. RCOG says your clinic should give you full written information about OHSS and a 24-hour help number.
6. Have paracetamol in the house, not ibuprofen, and ask the clinic to confirm what they want you to take.

When to seek help

The NHS advises contacting your fertility clinic or NHS 111 as soon as possible if you have pain and bloating in your abdomen, are feeling or being sick, feel faint, are coughing up blood, have vaginal bleeding or a brown watery discharge, or have pain or discomfort passing urine or opening your bowels. It advises calling 999 or going to A and E if you have difficulty breathing, pain in your chest or upper back, are very thirsty and passing much less urine than usual, have swelling anywhere on your body, have tummy pain low down on one side, or have pain in the tip of your shoulder, because these can be signs of severe hyperstimulation or an ectopic pregnancy. Do not drive yourself.

The HFEA's instruction on this is worth quoting for the days when you are talking yourself out of ringing: never feel you are wasting the clinic's time.