Overview
During IVF embryo transfer, it is easy to focus on injections, scans, and the transfer itself. But before the embryo reaches the uterus, it spends several important days in the IVF laboratory. The lab environment and the way embryos are handled can play an important role in their safety and development.
This article looks at closed IVF systems and open IVF systems, the conditions maintained in an embryology lab and how embryos are handled before transfer. It also explains how IVF embryo transfer works in simple terms, so you know what happens to your embryo before transfer day.
Table of Contents
- What Are Closed and Open IVF Laboratory Systems?
- Closed vs. Open IVF Labs: Key Differences
- How Do Closed IVF Systems Help Protect Embryos?
- Open vs Closed Vitrification: Which Is Right for Your Lab?
- The Effect of Open and Closed Oocyte Vitrification Systems on Embryo Development
- What Should I Look for in a Fertility Clinic's Embryology Lab?
- What Happens to Your Embryos Inside an IVF Laboratory?
- How Does the IVF Laboratory Affect Embryo Health?
- What Is the Role of Embryologists in Protecting Embryos?
- Does a Closed IVF System Improve IVF Embryo Transfer Outcomes?
- IVF Embryo Transfer: What Happens After Laboratory Culture?
- Conclusion
What Are Closed and Open IVF Laboratory Systems?
The main difference between these systems is how the embryo is protected during freezing and storage.
What Is a Closed IVF System?
In a closed IVF system, the embryo, egg or sperm is kept inside a sealed carrier during freezing and storage. It does not come into direct contact with liquid nitrogen or the surrounding environment. This can reduce the risk of contamination, particularly because storage tanks may contain samples from many patients.
What Is an Open IVF System?
With an open IVF system, the sample comes into direct contact with liquid nitrogen during vitrification, the rapid freezing method used in IVF. This allows very fast cooling and has been used successfully in fertility treatment for many years. Open systems are still widely used by fertility clinics.
Closed vs. Open IVF Labs: Key Differences
Both systems are designed to protect embryos, but they handle freezing and storage differently.
- Liquid nitrogen: Open systems expose the sample directly to liquid nitrogen, while closed systems keep it sealed.
- Cooling: Open systems allow very rapid cooling. Closed systems also vitrify embryos effectively, although the process can differ slightly.
- Contamination: Closed systems provide an additional barrier between the sample and the shared storage environment.
- Handling: Open systems can be quicker and more straightforward for embryologists to work with.
- Treatment outcomes: Studies generally report similar pregnancy and live birth outcomes with both approaches.
How Do Closed IVF Systems Help Protect Embryos?
A closed IVF system keeps the embryo sealed during freezing and storage, so it does not come into direct contact with liquid nitrogen. This creates an extra barrier against possible contamination from a shared storage tank. For this reason, some clinics use closed systems as an added infection-control measure for all patients, including those with certain infections.
Open vs Closed Vitrification: Which Is Right for Your Lab?
Vitrification is the rapid-freezing method used to preserve embryos for later use. Both open and closed systems use the same basic approach, but the embryo is handled differently during freezing.
How Open Vitrification Works
With an open system, the embryo is placed on a carrier and directly immersed in liquid nitrogen. The very rapid cooling helps prevent damaging ice crystals from forming inside the cells.
How Closed Vitrification Works
A closed system seals the embryo inside a straw or capsule before freezing. The container is cooled by the liquid nitrogen rather than exposing the embryo directly to it. Cooling may be slightly slower, but modern closed devices are designed to achieve effective vitrification.
Safety and Contamination Considerations
Laboratory studies have shown that open devices can pick up contamination from liquid nitrogen within seconds of contact, which is why closed systems are considered the safer choice from an infection control point of view. However, real world evidence of actual disease transmission between stored samples remains extremely rare.
What Research Says About Open and Closed Vitrification
A 2018 systematic review published in the journal Reproductive Biology and Endocrinology compared open and closed vitrification across a dozen studies and found broadly similar survival and pregnancy rates between the two systems, though the authors noted that closed systems carry a clear safety advantage for infection control. Separately, a 2021 study published in the Journal of Assisted Reproduction and Genetics found that a high security closed device performed just as well as an open system across fertilisation, pregnancy and miscarriage rates, while offering added protection against viral contamination, a finding that became especially relevant during the COVID-19 pandemic.
The Effect of Open and Closed Oocyte Vitrification Systems on Embryo Development
A 2024 study in the Journal of Clinical Medicine compared open and closed vitrification systems using data from 23 studies. The researchers found no significant difference between the two systems when they were compared directly.
However, when each method was compared with fresh, unfrozen eggs, the closed system showed a smaller reduction in blastocyst formation. This suggests it may have a slight advantage during later embryo development, although the researchers stressed that more evidence is needed before drawing firm conclusions.
What Should I Look for in a Fertility Clinic's Embryology Lab?
When choosing a fertility clinic, it is worth asking a few simple questions about its embryology lab:
- Does the lab use open or closed vitrification, and why?
- How is air quality managed in the embryo culture area?
- How often are incubators and other equipment serviced and calibrated?
- How experienced is the embryology team?
- What are the clinic's success rates for patients in your age group and with similar diagnoses?
What Happens to Your Embryos Inside an IVF Laboratory?
After fertilisation, embryos are kept in specialised incubators that provide controlled conditions for growth. Embryologists monitor their development, sometimes using time-lapse imaging so the embryos can be observed without frequent handling.
Around days three to five, embryos are assessed for their development and appearance. One may then be selected for IVF embryo transfer, while suitable embryos can be frozen through vitrification for future treatment.
How Does the IVF Laboratory Affect Embryo Health?
The air in an embryology lab is important. Everyday products such as cleaning agents, perfumes, furniture and cosmetics can release volatile organic compounds (VOCs). A mini review published in Therapeutic Advances in Reproductive Health noted that some VOCs may be harmful to developing embryos.
This is why IVF labs commonly use measures such as HEPA filtration, positive air pressure and restrictions on scented products, smoking and cosmetics around embryo culture areas.
What Is the Role of Embryologists in Protecting Embryos?
Embryologists handle embryos at every stage, from fertilisation and culture to freezing and transfer. Apart from carefully managing temperature, timing and handling, they follow strict hygiene procedures to keep the lab environment stable.
They also monitor incubators and other equipment closely so that any problem can be identified quickly. Their experience and attention to detail are an important part of maintaining embryo safety during IVF treatment.
Does a Closed IVF System Improve IVF Embryo Transfer Outcomes?
A closed system can provide extra protection during embryo storage. However, it does not necessarily increase pregnancy rates.
Factors That Influence Embryo Transfer Outcomes
The vitrification system is only one part of the picture. A 2026 study in Clinical and Experimental Reproductive Medicine, involving more than 700 single blastocyst transfer cycles, found that embryo quality had a greater effect on pregnancy outcomes than how quickly the embryo reached the blastocyst stage. Maternal age, embryo grade, endometrial thickness and transfer timing are also very important.
Why Laboratory Technology Is Only One Part of IVF
Even a well-equipped embryology lab cannot overcome factors such as egg quality, sperm quality, or an unfavourable uterine lining. Laboratory systems help protect embryos, but they cannot change the underlying quality of the embryos produced.
Why Closed Systems Do Not Guarantee Pregnancy
A closed system adds an extra layer of protection against possible contamination during freezing and storage, but it cannot guarantee pregnancy. Outcomes depend on several factors, including embryo quality, the uterine environment, and individual patient factors.
IVF Embryo Transfer: What Happens After Laboratory Culture?
Once the embryo has been cultured and graded, the IVF embryo transfer is usually a quick procedure. A thin catheter is used to place the embryo into the uterus, usually with ultrasound guidance. Anaesthesia is normally not needed.
After a short rest, you can usually go home. A pregnancy blood test is generally done around 10 to 14 days later. By this stage, the embryo has already spent several days under carefully controlled laboratory conditions.
Conclusion
Both closed and open IVF systems help protect embryos, although they work in different ways. Closed systems provide an extra barrier against contamination. On the other hand, open systems allow very rapid cooling during vitrification. Research suggests that pregnancy outcomes are broadly similar, although some studies show that there are possible safety or embryo-development advantages with closed systems.
For your IVF embryo transfer, the system itself is only one part of the picture. The quality of the embryology lab, the experience of the team, and your individual circumstances are also important. Discussing these factors with your fertility specialist can help you understand how your clinic handles and protects embryos.