In the embryology laboratory of the Institute of Life IASO, embryos are cultured in embryoscopes with time-lapse, a technology that records their development around the clock without the embryos having to be taken out of the incubator.
Embryoscope time-lapse monitoring technology makes it possible to have:
- Continuous monitoring of the embryos with a built-in camera, so that their culture remains undisturbed, without removing them from the incubator for examination under the microscope.
- Stable culture conditions, with fewer changes in temperature and gas composition and less handling.
- Detailed morphokinetic assessment: the images are analyzed based on the timing of each cell division and on morphology, and the embryos are ranked so that the one to be transferred first can be chosen.
- Collection of data that are also used by newer assessment tools based on artificial intelligence (AI).
Time-lapse gives the embryologist more information on which to base a decision. It does not, however, guarantee a pregnancy. Large clinical studies have not shown a clear increase in live birth rates compared with careful conventional assessment, and the chance of success depends mainly on the woman’s age and the quality of the eggs and sperm.
What time-lapse technology is
A time-lapse incubator is an embryo culture incubator with a built-in camera and microscope. It photographs each embryo every few minutes and combines the images into a video, from fertilization to the blastocyst stage. This way, the embryologist sees the whole course of development, not isolated snapshots.
How it differs from conventional culture
In conventional culture, embryos are taken out of the incubator once a day to be assessed under the microscope. Each time they are taken out, there are small changes in temperature and gas composition. With time-lapse, the embryos stay undisturbed in stable conditions, while events that would otherwise be missed are recorded: the exact timing of each cell division, abnormal divisions, and the rate at which the blastocyst forms.
When it is most valuable
- When there are several embryos with good morphology and one must be chosen for embryo transfer.
- For couples with repeated implantation failure, where every extra piece of information counts.
- When a single embryo transfer is planned, to avoid a multiple pregnancy.
- In combination with embryo cryopreservation, to rank the order in which the embryos will be used.
What to realistically expect
Time-lapse is a tool for selection and for stable culture conditions. It does not improve the quality of an embryo, nor does it replace preimplantation genetic testing, since it does not check the chromosomes. The success of a cycle still depends mainly on the woman’s age and the quality of the eggs and sperm. Whether it suits your case is something you will discuss with your doctor and embryologist as part of your IVF (in vitro fertilization). See also the new embryology techniques in use today.
Morphokinetics: what exactly the camera records
The term “morphokinetics” combines two things: what the embryo looks like (morphology) and when each step of its development happens (kinetics). Continuous recording allows the embryologist to note, to the minute, time points that simply cannot be seen with conventional observation.
The key time points
- Appearance and disappearance of the pronuclei: confirms that fertilization took place normally, with one set of chromosomes from the egg and one from the sperm.
- First divisions: the time the embryo needs to reach 2, 3, 4 and 8 cells, as well as the interval between divisions.
- Compaction and morula: the stage at which the cells start to bind tightly to one another.
- Start and completion of the blastocyst: when the cavity forms and when the embryo begins to expand.
Findings that only continuous recording reveals
- Direct cleavage: when one cell divides directly into three instead of two. Embryos with this finding generally have a lower chance of implantation.
- Reverse cleavage: when two cells that have just divided fuse back together.
- Multinucleation: cells with more than one nucleus in the early stages.
- Fragmentation dynamics: fragments of cytoplasm that appear and are sometimes reabsorbed, something a single look can misinterpret.
None of these findings “condemns” an embryo on its own. They serve as extra information that helps set the order of priority.
Ranking algorithms and artificial intelligence in embryo selection
Data from thousands of embryos with known outcomes have made it possible to build models that score each new embryo based on its morphokinetic features. The newest systems use artificial intelligence, which “learns” directly from the images without a person having to define what to look for.
- Advantage: assessment becomes more objective and more consistent between different embryologists.
- Limitation: many models have been tested mainly retrospectively, on data from the laboratory that created them. Their performance in other populations is not always the same.
- The embryologist’s role remains central: the algorithm suggests, the experienced professional decides, taking the couple’s history into account.
What studies show about time-lapse
Time-lapse technology belongs to a category known internationally as “add-ons,” meaning additional techniques on top of standard IVF. For these techniques, scientific societies require clear evidence.
- Systematic reviews have not shown with certainty that selecting embryos with time-lapse increases the birth rate compared with careful conventional assessment. A large randomized trial published in 2024 found no difference in live births.
- There is no evidence that the method harms embryos or the children who are born.
- The benefit of undisturbed culture and better laboratory organization is considered reasonable, but it is hard to measure in terms of pregnancy rates.
Put simply: time-lapse is safe and provides more information. It is not a magic tool, though, and the decision to use it should be based on honest information.
The embryos’ journey from egg retrieval to transfer, day by day
The days after the egg retrieval are full of waiting. When you know what happens in the laboratory each day, the embryologist’s updates become easier to understand.
- Day 0: the eggs are fertilized, either by conventional IVF or by ICSI, and placed in the incubator.
- Day 1: fertilization is checked. Not all eggs fertilize, and this is expected. Usually some of the mature eggs do not produce a normal zygote.
- Days 2 to 3: the embryo has about 4 to 8 cells. Some embryos stop dividing at this stage.
- Day 4: the cells compact and the morula forms.
- Days 5 to 6: the embryos with the best potential reach the blastocyst stage. From these, the one to be transferred is chosen, and any remaining good-quality embryos are frozen.
The gradual drop in numbers from eggs to blastocysts is normal and happens in every laboratory. It is the natural selection that takes place in the body anyway; here we simply get to see it.
When time-lapse offers less
The technology does not have the same value for every couple. The extra information is useful mainly when there is a choice among several embryos.
- When there are one or two embryos: the embryos will be transferred or frozen anyway, so ranking has little practical importance. Stable culture remains a benefit.
- In mild protocols, such as mini IVF, where the number of eggs is small from the outset.
- When genetic testing is already planned: chromosomal information usually carries more weight in the selection, although the two can work together.
Questions you can ask the embryologist
Embryologists are usually happy to explain what they see. Some useful questions:
- How many eggs were mature and how many fertilized normally?
- Were there any findings, such as direct cleavage or multinucleation, that affect the order of selection?
- On which day is the transfer recommended, and why?
- How were the frozen embryos graded, and in what order will they be used?
- If no embryo reaches the blastocyst stage, what does that tell us about the next cycle?
Understanding how your embryos developed does not change the result, but it helps you make informed decisions about the next step.
How time-lapse is combined with other embryology techniques
Time-lapse is rarely used on its own. In everyday practice it works together with other laboratory techniques:
- Culture to the blastocyst stage: continuous monitoring is most useful when the embryos stay in the incubator for five or six days, because more information is gathered.
- Biopsy for genetic testing: a few cells can be taken from the trophectoderm of embryos that reach the blastocyst stage. Morphokinetics helps choose the right time for the biopsy.
- Vitrification: embryos that are not transferred are frozen in order of priority, so that at the next transfer the one with the best prospects is thawed first.
- Single embryo transfer: the more confident the selection, the more readily the couple accepts transferring a single embryo, which is the safest choice for mother and child.
The goal is not to use every available technique, but the ones that truly make sense for the specific case.
Beyond the camera: what makes embryo culture reliable
Equipment is only one part. The quality of an embryology laboratory is judged mainly by how consistently its procedures are followed every day, for every couple.
- Continuous monitoring of conditions: temperature, pH and gas concentration in the incubators are recorded and backed by alarm systems.
- Backup: power and gases with an alternative supply, so that a failure does not affect the culture.
- Sample identification: double checking or an electronic system at every transfer of eggs, sperm and embryos.
- Quality indicators: regular monitoring of fertilization rates, blastocyst development and survival after thawing, so that any deviation is spotted early.
- Staff training: embryologists periodically check how well their assessments agree, to reduce subjectivity.
Time-lapse is added on top of this foundation. It does not replace it. If you want to understand how a laboratory works, ask how it monitors its own quality indicators and how it keeps couples informed at each stage of culture. Transparency on these points often says more than any equipment list.
When it makes sense to discuss time-lapse culture
Time-lapse is not necessary for every cycle. There are, however, cases where the information it provides can help the team make better-informed decisions, mainly when one embryo has to be chosen among several that look similar in morphology.
- Several good-quality embryos: morphokinetic assessment adds one more criterion for the order of transfer and freezing.
- Previous cycles without implantation: continuous recording can reveal abnormal divisions that are not visible in isolated observations.
- Culture to the blastocyst stage: the more days the embryos stay in the laboratory, the more useful it is not to disturb their conditions.
- Combination with preimplantation testing: in cycles with preimplantation genetic testing, time-lapse data help with the choice among genetically normal embryos.
On the other hand, when one or two embryos are expected, the extra information rarely changes the decision. Ask the embryologist whether, in your case, time-lapse will make a practical difference to embryo selection or whether conventional assessment is enough. An honest answer to this question also says a lot about the unit itself.
For a personalized assessment of your case, book an appointment with Dr. Panagiotis Polyzos at his office in Athens or Volos.
Frequently Asked Questions
What is an embryoscope?
It is an incubator with a built-in camera that continuously records the development of the embryos, without them having to leave the protected culture environment.
Is time-lapse safe for embryos?
Yes. It uses low-intensity light for fractions of a second, and the total exposure is lower than with conventional observation under the microscope.
Does it increase the chances of pregnancy?
It offers more stable conditions and more information for choosing the embryo. Large studies have not shown a clear increase in birth rates compared with careful conventional assessment, so the decision to use it is made on an individual basis.
Does it replace preimplantation genetic testing (PGT)?
No. Time-lapse assesses morphology and the rate of development, while PGT checks the embryo’s genetic material. The two methods can be combined.
Can I see the video of my embryos?
In many units, yes. Ask your doctor or embryologist whether this option is available.
What does it mean when an embryo stops developing?
It is common and does not necessarily mean that a mistake was made in the laboratory. Many embryos stop because they have chromosomal abnormalities or energy problems in the egg. Time-lapse simply records when and how it happened, information that can help in planning the next cycle.
Do I need to do anything differently if time-lapse is used?
No. Stimulation, egg retrieval and embryo transfer are carried out exactly as in any IVF cycle. The difference concerns only the way the embryos are cultured and assessed in the laboratory.
Is time-lapse charged separately?
It depends on the unit. In some centers it is included in standard culture, while in others it is charged as an additional service. Ask for written information about what the cost of your cycle includes before you start.
Can time-lapse predict whether I will have a miscarriage?
Not with certainty. Some morphokinetic features are associated with a lower chance of implantation, but miscarriage is often caused by chromosomal abnormalities that are not visible in the images. For that information, genetic testing of the embryo is needed.
