Results of the Survey "Embryo Culture and Catheter Loading"

Results of 161,300 IVF Treatment Cycles (265 centres from 71 countries)

It is widely accepted that the technique of embryo transfer has a crucial impact on the success of implantation in IVF. Discussions with clinicians from different IVF units have revealed that embryo transfer is performed differently in different clinics. In addition, it seems that at present there is no uniform practice regarding the preferred oxygen concentrations (5% or 20%) to be used in human embryo culture systems. Studies that evaluated the effect of oxygen concentration on embryo development in the human are controversial.

The below survey was suggested and conducted by

Irit Granot PhD, Laboratory Director and Research Coordinator of the IVF Unit, Kaplan Medical Center, Rehovot, Israel


Gabor Vajta, MD, PhD, DSc Vajta, Embryology Consulting, RVT, Australia

Anat Safran, PhD, Apirion - Embryology Consultation, Israel and Scientific Director, InviMed, European Center of Motherhood, Warsaw, Poland





Geographic region
No. of unites
No. of cycles
South America
Australia and NZ

The statistics are based on the number of cycles each unit performed and not on the number of units.

In the vast majority (94%) of clinics the embryologist loads the catheter.

Almost all of the units (97%) prefer a catheter with the orifice on its top.
Almost half of them use a catheter marked for clear ultrasound view.

Most units transfer embryos in the medium corresponding to the stage of the embryo at the time of transfer (42%) or in blastocyst medium in all stages (32%).

Most units wash the catheter before loading the embryos.

There is a large variety of methods in which the embryos are loaded into the catheter.
Medium-air-embryo-air-medium is the most used method (42%).

Virtually everyone loads all of the embryos in the same drop of medium.

In most units (68%), the final volume of medium in the catheter is up to 0.3 ml.

In most units, the time that the embryos remain in catheter does not exceed 60 seconds.

Most physicians inject the embryos into the uterus very slowly.
However a considerable number of physicians inject the embryos rapidly.

All catheters are checked after embryo transfer.

The predominant method for checking the catheter is to observe it
under the microscope and then wash it.

The practice of using reduced oxygen concentrations is almost equally divided between those who use it in combination with the two gas system and those who do not use it at all.
Using only three gas system is less frequent.

In most clinics using reduced oxygen concentrations, it is used throughout the entire culture period.

The practice of using sequential media is still highly dominant also when reduced oxygen concentrations are used.

Using reduced oxygen concentrations is applied in most clinics for the entire patient population.

When applying the system of reduced oxygen concentrations, the entire cohort of embryos from patients chosen are cultured under these conditions.
Usually, no attempt is made to divide the embryos of these patients between the two culture systems

It is usually advised by the companies offering single step media to transfer the embryos into dishes containing fresh equilibrated media on days 1, 3 and 5 of culture. Nevertheless, only approximately a quarter of clinics using single media for the entire culture period follow these recommendations.

Growing human embryos to the blastocyst stage singly or in groups for the entire culture period is similarly divided between the clinics.

Comment by: Juergen Liebermann, PhD, HCLD,IVF Laboratory Director | Fertility Centers of Illinois, Chicago Illinois 60610

Today, IVF is performed worldwide in different ways with similar outcomes. This survey confirms once again, that some techniques involved in embryo culture or embryo transfer are established and used by the majority of IVF centers. However, other techniques are equally used around the world achieving the same endpoint – getting patients pregnant at a high percentage. At the end of the day, it is important to realize, that regardless of the complexity of IVF as a whole, every lab has to define a way to provide good patient care combined with excellent outcome. Simplicity should be considered as a major part of this process.