By Andrea Rodrigo BSc, MSc (embryologist), Blanca Paraíso MD, PhD, MSc (gynecologist), Gorka Barrenetxea Ziarrusta MD, PhD (gynecologist) and María de Las Heras Martínez BSc, MSc (clinical embryologist).
Last Update: 09/19/2018

Ovum pick-up (OPU), which medical term is follicular or follicle puncture, is a key step in the process of in vitro fertilization (IVF). It is a surgical procedure required for harvesting the oocytes from the ovarian follicles. It is a simple, short intervention which is done under anesthesia (sedation).

Follicle aspiration procedure step by step

Each month, an egg is released from the ovary naturally during a process called ovulation. When a woman undergoes IVF, she is prescribed a hormone therapy to induce ovulation and trigger the maturation and production of multiple oocytes.

However, in order for the eggs to be properly fertilized in the laboratory, collection should be done before they are released from the ovary spontaneously, as in that case it would be hard for the specialist to locate them. So, follicle puncture should be carried out just before natural ovulation.

Given that the ultimate goal is to harvest the eggs when their maturation level is the appropriate for fertilization (at the metaphase II stage), scheduling the puncture for the ideal moment is crucial. To this end, follicle growth is monitored while on ovulation induction treatment. Follicle size is measured by transvaginal ultrasound and also by checking the estradiol levels in blood.

Ultrasound monitoring should be done every two days. For further information about the process of Controlled Ovarian Stimulation (COS), please visit the following post: Ovulation induction in IVF.

Follicles are considered to be mature, which is to say, they contain a mature egg on the inside, when their diameter measures above 16-18 millimeters. Once this size is reached, self-administering hCG shots to reach the final stage of maturation is necessary. It helps triggering ovulation within 36-48 hours after being administered.

After that, OPU can be scheduled for just a few hours before ovulation, i.e. within 30-34 hours before the administration of hCG injections. This way, we get the eggs to remain inside the follicles for the harvesting procedure.

Even though the timeline may vary from clinic to clinic, the following are the basic steps followed:

Hospitalization

Patients are hospitalized in the clinic on that day, around 1 hour before surgery. A preoperative evaluation and a pre-anesthesia consultation are required prior to hospitalization. Their results should be provided before getting started with the procedure.

Being relaxed and having fasted for at least 6 hours before follicle puncture is crucial. It is a simple procedure, which only lasts 30 minutes approximately. Patients can return home that day.

Anesthesia

After entering the gynecological consultation by themselves, patients lie in lithotomy position and sedation will be administered by an anesthesiologist.

Though it is not a high-risk surgery, sedation is required to prevent it from being painful, thereby making the retrieval process easier for the gynecologist.

Follicle aspiration

Once the patient is “asleep”, the gynecologist proceeds with ultrasound-guided follicle aspiration. The ultrasound-guided aspiration needle is inserted through the vagina to get into the follicles and aspirate the follicular fluid (FF) contained within.

Oocytes float freely in the FF, which is directly put in test tubes at a temperature of 37 °C. Always keeping this temperature constant, the tubes are moved to the laboratory, where embryologists will analyze it in the search for mature eggs.

All mature eggs detected are fertilized so that they hopefully result in viable embryos with implantation potential after being transferred to the mother’s womb.

Recovery: Is bed rest necessary?

When the gynecologist finishes puncturing the follicles, the anesthetic is stopped. Patients are moved to a room for recovery until anesthesia wears off. They should rest only for a few hours until they recover fully from the effects of anesthesia.

After a reasonable time period, and after checking everything is okay, patients can return home. Discomfort is a common symptom after egg retrieval, but it is not severe and will not prevent you from continue with your normal lifestyle the following day.

Potential risks and side effects

Ovum retrieval is a simple surgical procedure done under mild anesthesia or intravenous sedation. Thus, the number of risks involved is low. There is only a small chance for anesthesia to cause some side effects such as bloating, sickness, low blood pressure or vomiting.

As for the potential risks derived from surgery, pelvic organ injury is a major risk, which at the same time may lead to bleeding and infection of the reproductive organs.

For the prevention of these complications, patients should have a thorough female pelvic ultrasound exam done at the gynecologist’s office to prevent fluid from accumulating in the pouch of Douglas.

Preparing for egg retrieval

Having fasted completely overnight before follicle puncture is a basic requirement for it to be properly carried out, avoiding adverse reactions and unexpected events to occur.

Patients are advised to visit the clinic with company, since they may feel a bit confused after the procedure as a consequence of sedation.

Although women can leave the clinic a few hours after having had their eggs retrieved, it is advisable for them to wait for a reasonable period of time to recover fully from the effects of anesthesia.

Discomfort or light vaginal bleeding are common symptoms after this type of surgery. Rest is recommended only during the day of surgery, avoiding great efforts, so that the organism is able to recover fully.

Interview to Embryologist María de Las Heras & Dr. Gorka Barrenetxea

María de Las Heras Martínez, BSc, MSc, and Gorka Barrenetxea, MD, PhD, explain in this video what is follicle puncture or oocyte retrieval, the improvements achieved today and the clinical uses of the procedure.

FAQs from users

Is there any serious risk associated with the egg retrieval procedure?

By Blanca Paraíso MD, PhD, MSc (gynecologist).

Follicular puncture or oocyte retrieval is a mild procedure that involves little risk of complications.

The most severe risks that can occur during or after this procedure are damage to pelvic organs (intestines, bladder…), bleeding, or infections. These complications are very rare, as it is an ultrasound-guided procedure, which means that the gynecologist can monitor the sites being approached.

Other side effects, though less severe, include dizziness and vomiting due to anesthesia, or abdominal pain during the first days after the procedure.

When is egg retrieval required?

By Andrea Rodrigo BSc, MSc (embryologist).

Follicle puncture is done only when retrieving the eggs from the ovary is needed, either for in vitro fertilization with own or donated eggs. It is also done for fertility preservation, as it involves obtaining and freezing the eggs for later use.

Is the egg harvesting process painful?

By Andrea Rodrigo BSc, MSc (embryologist).

Ovum pick-up is done under anesthesia, and therefore it does not hurt at all. However, it is possible for patients to feel a mild discomfort before the procedure due to an increased ovarian size caused by ovarian stimulation.

Can egg retrieval be done without anesthesia?

By Andrea Rodrigo BSc, MSc (embryologist).

It is a possibility, but the procedure would be too painful. Besides, if it hurts, the gynecologist cannot proceed with aspiration accurately, so the results would be poorer, the number of complications would increase, and the process would take longer.

Is it normal to feel abdominal pain after egg retrieval?

By Andrea Rodrigo BSc, MSc (embryologist).

Yes, many women feel some mild discomfort around the area of the abdomen and the vagina as a side effect of follicle puncture. Normally, pain only lasts for one or two days, but it diminishes eventually until it disappears completely within a few days.

Is the egg collection procedure carried out in exactly the same way to the ICSI?

By Andrea Rodrigo BSc, MSc (embryologist).

Yes, conventional IVF and ICSI differ in the way the egg is fertilized, which is to say, at the moment of fusing the egg and the sperm, but the remaining steps are exactly the same.

Ovarian stimulation, ovum pick-up, embryo culture and embryo transfer do not change at all. More detailed information here: In vitro fertilization and ICSI.

Authors and contributors

 Andrea Rodrigo
BSc, MSc
Embryologist
Bachelor's Degree in Biotechnology from the Polytechnic University of Valencia. Master's Degree in Biotechnology of Human Assisted Reproduction from the University of Valencia along with the Valencian Infertility Institute (IVI). Postgraduate course in Medical Genetics. More information
 Blanca Paraíso
MD, PhD, MSc
Gynecologist
Bachelor's Degree in Medicine and Ph.D from the Complutense University of Madrid (UCM). Postgraduate Course in Statistics of Health Sciences. Doctor specialized in Obstetrics & Gynecology, and Assisted Procreation. More information
License: 454505579
 Gorka Barrenetxea Ziarrusta
Bachelor's Degree in Medicine & Surgery from the Public University of Navarra, with specialty in Obstetrics and Gynecology from the University of the Basque Country. He has over 30 years of experience in the field and works as a Titular Professor of Obstetrics & Gynecology at the University of the Basque Country and the Master's Degree in Human Reproduction of the Complutense University of Madrid. Vice-president of the SEF. More information
License: 484806591
 María de Las Heras Martínez
BSc, MSc
Clinical Embryologist
Bachelor's Degree in Biology from the Pompeu Fabra University and Master's Degree in Biology of Reproduction & Assisted Reproductive Technologies from the Autonomous University of Barcelona, in collaboration with Instituto Universitario Dexeus. Master's Degree in Biochemical Research from the Basque Country University. Clinical Embryologist by the ESHRE. More information