Which solution (culture medium) works best to help embryos develop before they are implanted in a womb during assisted reproduction?
-
This updated review assessed special solutions (culture media) that are important for helping embryos develop in assisted reproduction technology (ART) treatments used for women who cannot get pregnant naturally. Currently, we do not know which culture medium gives the best chance of giving birth to a live baby. One study showed that an embryo culture medium called G5 probably leads to more live births than one called HTF, but the other studies did not show clear differences in success rates between different culture media.
-
The evidence is limited because the studies tested different culture media and their results could not be combined. Many studies had weaknesses, such as small numbers of people taking part. More, well-designed studies are needed to find out which embryo culture medium works best.
A woman who cannot get pregnant naturally may use assisted reproductive technology (ART) treatments, such as IVF (in vitro fertilization), in which eggs are fertilized by sperm outside the body. Supporting the embryo this creates to develop (culture) is a very important part of IVF treatment. The embryo is placed in a special solution called an embryo culture medium. This medium provides nutrients and helps the embryo grow in the laboratory until it is transferred to the womb (uterus) or frozen for later use. There are many different embryo culture media.
Why is there no agreement about which culture medium works best?There is currently no clear agreement on which type of embryo culture medium gives the best chances of having a live baby. The available research does not give enough reliable information to clearly choose one culture medium over another. This makes it difficult for doctors and patients to know which option to use.
What did we want to find out?We wanted to know whether different types of human embryo culture media affect the chances of having a baby or an ongoing pregnancy (pregnancy confirmed by heartbeat on ultrasound) for women undergoing IVF treatments.
What did we do?We searched for studies that compared different embryo culture media available for use during IVF treatments. We looked at the results of studies for all the measurements we think are important. We considered the reliability of each study based on how it was designed and conducted. We made a judgement about how certain we were about the evidence for each important measure.
What did we find?We found 26 relevant studies, eight of which evaluated the most important measures, such as live birth or ongoing pregnancy. Another five studies are in progress, and there are 60 studies that we have not been able to include because they are only published as short summaries without enough information. It was not possible to combine any of the studies' results because no two studies compared the same culture media.
Main resultsEight studies (3315 women) of the 26 studies included in the review reported live birth or ongoing pregnancy.
Most studies did not find a clear difference between the culture media they compared. However, the two largest studies did find some differences that could be important.
One study showed that there was probably a 6% higher chance of having a live birth with G5 compared to HTF (836 women). Another study showed that there may be a 6% higher chance of having a live birth with EmbryoAssist plus GM-CSF (with low HSA (a low concentration of a protein in the blood called albumin)) compared to a version of EmbyroAssist without the GM-CSF (743 women), but we are very uncertain about this result, especially because the treatment was changed during the study.
The same studies found differences in ongoing pregnancy rates. One suggested that G5 probably increases the chance of ongoing pregnancy compared with HTF (836 women). The other suggested that EmbryoAssist plus GM-CSF (low HSA) may increase the chance of ongoing pregnancy compared with EmbryoAssist without GM-CSF (743 women), but we are very uncertain about this result.
The evidence is very limited and unclear, and we could not combine results from different studies. Further well-designed studies are needed to confirm the findings and determine if any specific culture medium improves treatment success.
What are the limitations of the evidence?-
Many studies included only a small number of women.
-
Some studies had problems with how they were designed.
-
A few studies assigned eggs or embryos (rather than women) to the groups being compared, or transferred embryos from different study groups to the same woman.
-
Most studies did not clearly describe the ingredients in the culture media.
-
Many studies did not report all important measures.
Overall, the evidence was mostly very uncertain because:
-
the studies could not be combined with each other;
-
the studies' results were not precise; and
-
the studies' results were not always worked out in the right way.
This review updates one published in 2015. The evidence is current to 28 August 2025.