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How the Embryology Laboratory at “Nadezhda” works
Interview with Stefka Nikolova, Chief Embryologist at “Nadezhda” Hospital and Head of the Embryology Laboratory.
24.11.2025 | 10:47
The Embryology Laboratory — the heart of the IVF Center at “Nadezhda” Hospital — is innovative, high-tech, aligned with global standards, continuously evolving, and supported by the expertise of embryologists with many years of professional experience.
Specially designed according to the workflow of IVF procedures, the laboratory is equipped with world-class technology, including two Embryoscopes and multiple incubators. Safety and quality control are ensured through the RI Witness system — the global gold standard for security in handling reproductive cells.
The Embryology Laboratory at “Nadezhda” offers the full range of assisted reproductive techniques, including conventional IVF and ICSI, as well as various specialized procedures related to eggs, sperm, and embryo culture.
The embryologists at “Nadezhda” have extensive experience — approximately 5,000 ART cycles are performed annually at the center. Their expertise also enables them to perform the highly specialized procedure of embryo biopsy for PGT testing, which is conducted on-site at “Nadezhda” Hospital.
Embryologist Stefka Nikolova has been part of the “Nadezhda” IVF Center team since 2005.
Since 2013, she has served as Senior Clinical Embryologist of the center, and since 2016 she has been Chief Embryologist and the responsible person for assisted reproduction at “Nadezhda” before the Executive Agency “Medical Supervision.”
Her professional interests include embryology, cryopreservation, PGT, quality control, time-lapse technologies, and non-invasive diagnostic methods in embryology.
Stefka Nikolova has been a member of ESHRE (European Society of Human Reproduction and Embryology) since 2006. Since 2014, she has been certified as a Senior Clinical Embryologist by ESHRE. She also served for four years as Bulgaria’s representative in the CNR (Committee of National Representatives) at ESHRE.
1. What distinguishes the embryology laboratory at “Nadezhda” Hospital?
Over the past 20 years, the Assisted Reproduction Center at “Nadezhda” has built a large team specialized in separate units with specific responsibilities — andrology and embryology. This allows us to focus carefully on every stage of the diagnostic and IVF process and provide the highest quality of care.
Unlike smaller centers where one or two biologists perform all procedures, we are a well-coordinated team with long-standing experience and constant communication with the treating physicians.
Of course, we rely on the latest technologies — we have state-of-the-art incubators, manipulators, and microscopes — but our true strength lies in our people: their professionalism, precision, and dedication.
2. What criteria must an embryology laboratory meet to be comparable to the best in the world?
A good laboratory is more than equipment — it requires meticulous control of every aspect of the environment in which we work: temperature, humidity, gas levels, and air purity. Every critical parameter is continuously monitored.
Each biologist undergoes extensive step-by-step training and regularly attends congresses and seminars to stay up to date with the latest scientific advancements.
An individualized approach to every patient is also essential — we adapt the methods we use according to the specific needs of each case.
3. How is the security of genetic material guaranteed in the “Nadezhda” laboratory?
Safety is our top priority. To guarantee this, we implemented the integrated RI Witness system, specifically designed for IVF laboratories. It tracks not only the pathway of each patient’s cells but also verifies correct matching.
The software is connected to our information system and receives preliminary information about the partners involved in each IVF procedure.
Every sperm and egg sample received is identified through a microchip containing patient information, and every activity performed with these samples is documented.
During fertilization, the system verifies whether the eggs and sperm being used belong to patients registered as a couple. It also checks that embryo transfer data matches the patient’s identity.
This gives us confidence that the genetic material is protected and traceable at every step.
4. What kind of team works in the IVF laboratories?
Our team includes clinical embryologists, andrologists, biologists, and laboratory technicians, all with extensive specialized training and certifications, including those from ESHRE.
Each specialist has clearly defined responsibilities — from monitoring and preparation of culture media to gamete processing and embryo transfer.
Team spirit and mutual trust are at the core of our work.
5. What equipment does the embryology laboratory use?
Our laboratory was specifically designed to follow the workflow logic of the IVF sector. During its construction, we considered even the smallest details.
We have three procedure rooms for egg retrievals and embryo transfers, each connected to a laboratory pass-through box for the rapid transfer of follicular fluids and embryo transfer catheters.
Communication between the embryologist and the reproductive specialist or midwife in the operating room is maintained through a hands-free system.
Each workstation is equipped with a microscope, micromanipulator, and computer. All patient information is stored in specialized software, allowing fast and continuous access.
We have multiple incubators, each serving a specific purpose, as well as two Embryoscopes that monitor embryo development 24 hours a day.
Prepared sperm samples from the Andrology Laboratory are transported directly to the embryology laboratory via a dedicated elevator system.
We also have a separate cryobox area specifically designated for freezing and thawing eggs and embryos, with direct access to a liquid nitrogen system.
We are very proud of the laboratory we have built. I believe that in our laboratory we truly individualize our approach to couples and continuously improve our work based on the experience gained from previous procedures.
We apply sperm selection methods based both on morphological criteria (high-magnification selection) and functional criteria (“Zona Test”).
Regarding egg quality, we add antioxidant factors to the culture media. Immature eggs are allowed to mature further under laboratory conditions and are fertilized depending on the specific case.
During embryo culture, we strive to minimize incubator opening and repeated handling. In many cases, we also use the Embryoscope — an advanced embryo culture and monitoring system — for detailed observation and analysis of embryo development using an integrated mathematical model, which helps us select embryos for transfer.
6. What additional procedures are performed at “Nadezhda” beyond standard IVF techniques?
At our center, we offer a number of innovative methods that increase the chances of success, including:
- Time-lapse embryo monitoring
- Preimplantation genetic testing (PGT-A)
- Sperm DNA fragmentation analysis
- Zona selection for choosing the healthiest sperm cells
- Addition of antioxidants to culture media to protect against oxidative stress
- Assisted hatching to facilitate implantation
- Cryopreservation of gametes for future use
We are also currently exploring the possibilities of implementing artificial intelligence in sperm and embryo selection.
7. Which hospital departments do you collaborate with most actively?
The Embryology Laboratory works closely with several key departments:
- Reproductive specialists — we discuss results daily and plan the next stages of procedures and treatment
- Andrology Laboratory — we coordinate sperm evaluation and selection methods
- Genetics Laboratory — we coordinate preimplantation embryo testing and consider monogenic disease carrier status during donor selection
- IVF sector midwives — we coordinate patient care and procedure scheduling
- Clinical laboratory, microbiology, and virology departments — we receive the laboratory results necessary for our work
This multidisciplinary collaboration helps us provide comprehensive and personalized care for every patient.
8. What are the scientific interests of your team and what challenges do you face?
Our scientific interests focus on genetics, improving gamete care, increasing embryo implantation potential, and applying artificial intelligence to enhance our work.
The challenges are significant, but they motivate us to seek innovative solutions and continuously improve our daily practice.
9. What does your personal work at “Nadezhda” involve?
Over the years, my role has evolved — I am no longer only in the laboratory but also responsible for organizational tasks such as document management, reporting, registry control, coordination of genetic material transportation, and patient consultations.
This allows my colleagues to focus more fully on laboratory work. Although I miss working directly with cells, I know my role is extremely important.
In addition, I am currently pursuing a PhD in the Department of Genetics at the Medical University of Sofia under the supervision of Prof. Hadzhidekova, Head of the Genetics Laboratory at “Nadezhda” Hospital.
Together, we are working on a highly interesting scientific project investigating genetic causes for developmental arrest in balanced embryos, which allows me to combine scientific research with clinical practice.
10. What recommendations would you give to patients beginning the journey of assisted reproduction?
I recommend that couples seek help in a timely manner if pregnancy has not occurred after one year of regular attempts (or after 6 months for women over 35).
It is important to consult a reproductive specialist so that the problem can be identified early. Sometimes very valuable time is lost in waiting, and fertility challenges may worsen with age.
IVF is not the only method for achieving pregnancy. In some cases, pregnancy occurs quite quickly after hormonal regulation, ovulation induction, insemination, or diagnostic and treatment procedures.
It is very important for patients to have patience and trust in the medical team. At “Nadezhda,” we give our very best — expertise, time, and personal care. Everyone who comes to us will be in good hands and will not be alone on their journey toward the child they dream of.
