World Embryologist Day: Why July 25 Is World IVF Day

Most IVF patients never meet the scientists working in the lab down the hall from the procedure room, and World Embryologist Day is the one day each year when clinics put those teams in the spotlight.

Embryologists handle eggs, sperm, and embryos at every stage of treatment, including the donated embryos families receive through embryo donation at Donor Nexus, and much of their work happens out of patients' view. If you've gone through IVF or are considering donor embryos, you've relied on an embryologist's work. This guide explains why the day falls on July 25, what embryologists do, which milestones shaped the field, and how the lab's work connects to donated embryos.

You'll also find a timeline of verified IVF and embryology firsts, updated figures on how many babies have been born through IVF, and a few simple ways to mark the day with your own clinic or family.

Why is World Embryologist Day on July 25?

World Embryologist Day falls on July 25 because Louise Brown, the first baby born through in vitro fertilization, was born on July 25, 1978.¹ Her birth followed years of work by Robert Edwards and Patrick Steptoe, whose research partnership turned IVF into a treatment that clinics could offer patients.¹ Edwards received the 2010 Nobel Prize in Physiology or Medicine "for the development of in vitro fertilization."⁴

Is World Embryologist Day an official holiday?

World Embryologist Day is an informal observance, and it's marked mainly by fertility clinics, laboratories, and organizations in the field. Clinics and lab suppliers publish posts about the day each July to celebrate Louise Brown's birth and the work of embryologists,^2,5 and the UK's fertility regulator, the Human Fertilisation and Embryology Authority, marked the day in 2025 with a trainee embryologist's account of a typical working day.⁶ You'll see it called World Embryologist Day, World IVF Day, Embryologist Day, or Embryology Day, depending on the clinic.

How many babies have been born through IVF?

An international analysis estimated that between 9,829,668 and 13,019,331 babies were born with the help of IVF and related assisted reproductive technology (ART) from 1978 through 2018, using data from 101 countries.³ Preliminary data from 2019 through 2023 suggest roughly 3 to 4 million additional births, for a total of about 13 to 17 million by 2024.^3,7

The same study estimated that Europe accounts for the largest share, about 3.6 to 4.5 million births, followed by Asia at 3.1 to 4.0 million and North America at 1.4 to 1.6 million, and that a baby conceived through ART is now born about every 35 seconds.³ For comparison, the 2010 Nobel announcement put the total at about 4 million, which shows how quickly the number has grown in the years since.¹

What does an embryologist do?

An embryologist is the laboratory scientist who handles eggs, sperm, and embryos during IVF, from the day of egg retrieval through freezing, warming, and transfer. Their work typically includes these responsibilities:

1. Maintaining the lab environment. Embryologists keep incubators and culture conditions stable. Many labs use time-lapse incubators, which photograph embryos as they grow so the team can follow their development without taking them out of a warm, steady environment.⁸
2. Preparing and assessing sperm. Before fertilization, the lab processes each sperm sample, a step often called sperm washing, to concentrate the most active sperm.^8,9
3. Fertilizing eggs, including ICSI. With intracytoplasmic sperm injection (ICSI), the embryologist uses a fine glass needle under a microscope to place one sperm directly inside each egg, a procedure CCRM Fertility describes as among the most challenging an embryologist performs.⁹
4. Culturing and grading embryos. After confirming which eggs fertilized, embryologists follow each embryo as it grows toward the blastocyst stage, which most reach on day 5 or 6 and some on day 7, and they grade embryos on how the cells look and how much fragmentation is present.^9,8 Our guide to embryo grading and what grades like 4AA mean explains those scores.
5. Performing embryo biopsy for genetic testing. For preimplantation genetic testing (PGT), including testing for abnormal chromosome numbers (PGT-A), the embryologist takes a small sample of cells from each blastocyst and sends it for analysis.⁹
6. Freezing and warming embryos. Vitrification is an ultra-fast freezing method that keeps damaging ice crystals from forming, and vitrified embryos stay in liquid nitrogen storage at -196°C until they're warmed for transfer.^8,17
7. Selecting embryos for transfer. When recommending which embryo to transfer, embryologists look at much more than the grade alone.⁸
8. Keeping records and verifying identity. Every dish and tube is labeled to the patient, and a second staff member independently checks each step that can't be undone.⁶

What happens in the embryology lab on transfer day?

On transfer day, the embryology team prepares the embryo, confirms it belongs to the right patient, and hands it off for the transfer itself. A trainee embryologist writing for the UK's fertility regulator described warming a frozen embryo two or more hours ahead of the transfer, which gives the lab time to confirm the cells came through the thaw and the embryo is expanding again.⁶ In her lab, radiofrequency identification (RFID) tags and labels showing three patient identifiers go on every dish and tube, and when it's time for the transfer, she places the embryo in the thin catheter the doctor passes through the cervix.⁶ Practices differ from clinic to clinic, so your own care team can walk you through how its lab handles each step.

Which milestones shaped IVF and embryology?

The milestones that shaped modern embryology began with the first IVF birth in 1978 and continued through embryo freezing, egg and embryo donation, genetic testing, and ICSI, all within about 15 years. Later advances in freezing and a steady rise in embryo donation followed.

Selected IVF and embryology milestones, verified against the original publications or official sources listed.

Key IVF and embryology milestones from 1978 to 2018. Sources: Nobel Prize 2010; Trounson et al. 1983; Trounson and Mohr 1983; Lutjen et al. 1984; Handyside et al. 1990; Palermo et al. 1992; Adamson et al. 2025.

Several of these firsts are still part of routine care. ICSI was first used for couples with severely impaired sperm in whom standard IVF and an earlier sperm-injection technique had both failed, and the 1992 report described four pregnancies, three of which continued and produced four healthy babies.¹⁵ The 1990 genetic diagnosis work biopsied embryos at the six- to eight-cell stage so that couples at risk of passing on X-linked conditions could transfer unaffected embryos, an approach that later testing methods built on.¹⁴

Embryo freezing matters for families today in a practical way, because the donated embryos families receive today were frozen during another family's IVF treatment. In a national analysis of US data, there were 21,060 frozen donated embryo transfers from 2004 to 2019, resulting in 8,457 live births.¹⁶ Among 8,773 transfers with known outcomes from 2016 to 2019, 53.4% resulted in pregnancy and 43.5% in a live birth, and a single embryo was the most common number transferred.¹⁶ Our guide to donor embryo success rates explains how those outcomes are measured.

Where does embryology meet embryo donation at Donor Nexus?

Embryology meets embryo donation at Donor Nexus in the lab at HRC Fertility in Southern California, where donated embryos are stored and where transfers take place. Embryos in the Donor Embryo Program are stored at HRC Fertility in Newport Beach and Encino and can't be shipped to outside clinics.¹⁸ Before transfer, the lab thaws your selected embryo, and in the rare case that it doesn't survive, the lab can thaw another embryo from the same profile or Donor Nexus can help you choose a backup profile.

The lab's work also shows up on the profiles you browse. Each profile lists the embryo information available, which may include embryo grading, the year the embryos were frozen, the stage at which they were frozen, whether an egg or sperm donor was involved, and genetic carrier results if screening was done.¹⁹ A profile might show, for example, a day 6 embryo graded XBBB, and our embryo grading guide explains what those letters mean. To see how the program works from browsing to transfer, visit our Donor Embryo Program page.

How can you mark World Embryologist Day?

You can mark World Embryologist Day with small gestures that recognize the people behind your treatment. A few ideas:

• Send a thank-you note or card to your clinic's embryology team.
• Share your family's story with your clinic or community, if you're comfortable doing so.
• Learn how your embryos were graded and ask your care team any questions you still have.
• If you have embryos in storage, use the date as a yearly reminder to review your storage agreement and options for leftover embryos.

Frequently asked questions about World Embryologist Day

When is World IVF Day?

World IVF Day falls on July 25 every year. The date marks the anniversary of Louise Brown's birth in 1978, and fertility clinics, laboratories, and patient communities use it to share stories, celebrate families, and thank the lab teams whose work most patients never see firsthand.

Is World Embryologist Day the same as World IVF Day or Embryology Day?

Yes, World Embryologist Day, World IVF Day, and Embryology Day all refer to the July 25 observance tied to Louise Brown's birth in 1978. Some clinics use World Embryologist Day to spotlight their lab teams, and others use World IVF Day to celebrate patients and families, so the name you see depends mostly on who's posting and what they want to highlight.

What does an embryologist do on transfer day?

On transfer day, the embryologist prepares your embryo, warming it ahead of time if it was frozen and checking that its cells survived and began to re-expand. Identity checks are witnessed before irreversible steps, and the embryologist loads the embryo into the transfer catheter and assists your doctor during the procedure.

How many babies have been born through IVF?

Researchers analyzing international registry data put the number at 10 to 13 million babies born with help from IVF and related assisted reproductive technology between 1978 and 2018. Adding preliminary figures through 2023 brings the estimated total to roughly 13 to 17 million by 2024.

If World Embryologist Day has you thinking about building your family with donor embryos, a good next step is to browse profiles and see what information the lab provides for each one. You can register for free at donornexus.com/registration to browse the donor embryo database, or contact our team at info@donornexus.com or +1 (949) 433-5635, Monday to Friday, 8 a.m. to 4 p.m. Pacific.

Sources

1. The Nobel Assembly at Karolinska Institutet. The Nobel Prize in Physiology or Medicine 2010: press release. October 4, 2010. nobelprize.org.
2. Hamilton Thorne. World Embryologist Day: celebrating the science of IVF. July 22, 2024. hamiltonthorne.com.
3. Adamson GD, Creighton P, de Mouzon J, Zegers-Hochschild F, Dyer S, Chambers GM. How many infants have been born with the help of assisted reproductive technology? Fertility and Sterility. 2025;124(1):40-50. doi:10.1016/j.fertnstert.2025.02.009.
4. NobelPrize.org. The Nobel Prize in Physiology or Medicine 2010: summary. nobelprize.org.
5. Bristol Centre for Reproductive Medicine. World Embryologist Day. July 25, 2024. fertilitybristol.com.
6. Human Fertilisation and Embryology Authority. World Embryologist Day, in the life: I love to perform transfers as it can be a really exciting and hopeful time for the patient. July 25, 2025. hfea.gov.uk.
7. UNSW Sydney Newsroom. Total IVF births soar to more than 13 million. July 28, 2025. unsw.edu.au.
8. Whitney E. The vital role of an embryologist in an IVF cycle. The Evewell. February 6, 2024. evewell.com.
9. CCRM Fertility. 5 procedures your embryologist performs in the IVF lab. July 22, 2025. ccrmivf.com.
10. Trounson A, Leeton J, Besanko M, Wood C, Conti A. Pregnancy established in an infertile patient after transfer of a donated embryo fertilised in vitro. British Medical Journal. 1983;286:835-838. pubmed.ncbi.nlm.nih.gov/6403104.
11. Trounson A, Mohr L. Human pregnancy following cryopreservation, thawing and transfer of an eight-cell embryo. Nature. 1983;305:707-709. doi:10.1038/305707a0.
12. EBSCO Research Starters. Birth of "Baby Zoe" is announced. ebsco.com.
13. Lutjen P, Trounson A, Leeton J, Findlay J, Wood C, Renou P. The establishment and maintenance of pregnancy using in vitro fertilization and embryo donation in a patient with primary ovarian failure. Nature. 1984;307:174-175. doi:10.1038/307174a0.
14. Handyside AH, Kontogianni EH, Hardy K, Winston RML. Pregnancies from biopsied human preimplantation embryos sexed by Y-specific DNA amplification. Nature. 1990;344(6268):768-770. doi:10.1038/344768a0.
15. Palermo G, Joris H, Devroey P, Van Steirteghem AC. Pregnancies after intracytoplasmic injection of single spermatozoon into an oocyte. The Lancet. 1992;340(8810):17-18. doi:10.1016/0140-6736(92)92425-F.
16. Lee JC, DeSantis CE, Boulet SL, Kawwass JF. Embryo donation: national trends and outcomes, 2004-2019. American Journal of Obstetrics and Gynecology. 2023;228(3):318.e1-318.e7. doi:10.1016/j.ajog.2022.10.045.
17. Practice Committees of the American Society for Reproductive Medicine and the Society of Reproductive Biologists and Technologists. A review of best practices of rapid-cooling vitrification for oocytes and embryos: a committee opinion. Fertility and Sterility. 2021;115(2):305-310. asrm.org.
18. Donor Nexus. Donor Embryo Program. Accessed September 2026. donornexus.com/embryo-donation.
19. Donor Nexus. Embryo donation process. Accessed September 2026. donornexus.com/embryo-donation-process.

Related reading

Embryo Grading ExplainedWhat blastocyst grades like 4AA and XBBB mean, and how much grade matters.Read the guideDonor Embryo Success RatesNational data and program outcomes for frozen donor embryo transfers, and how to read them.Read the guideDonor Embryo ProgramBrowse donor embryo profiles and see how the program works from selection to transfer at HRC Fertility.Visit the page