Embryo Culture and Transfer

In Vitro Fertilization Program

The ultimate goal of in vitro fertilization and embryo culture is to transfer high quality embryos that are capable of continued normal development and result in live births.  Achievement of this goal requires the following:

• Optimal in vitro culture conditions
• Reliable embryo selection criteria

• Minimize the risk of multi-fetal pregnancy

Optimizing In Vitro Culture Conditions

In the past decade a more detailed understanding of the embryo’s nutrient and environmental requirements has led to the formulation of culture media capable of supporting development of viable blastocysts (day 5).  Earlier culture media supported embryo development up to the 2- to 8-cell stage (day 2-3), but did not provide the complexity of nutrients required by later stage embryos. 

Embryo Selection Criteria

Embryo selection criteria are currently based on the rate of embryo development and embryo morphology (appearance).  Selection of embryos based on rate of development is similar to selection of the top finishers of a race with novice participants.  Selecting embryos at the one-cell or pronuclear stage is like picking the top finishers of the race before the starting gun.  As the race progresses, a select number of participants take the lead and spectators have a better indication as to which participants will finish the race first.  As with a race, a greater number of competitors (i.e. embryos) usually promote a better finishing time.   At the UIHC, we have found that we are able to optimize outcomes by limiting the stress the embryos incur in culture when less than 7 embryos are available and by increasing embryo selection through extended culture when more than 6 embryos are available.  We transfer the best embryo(s) on day 3 (6- to 8-cell stage) when fewer than 7 pronuclear-stage embryos are available.  We recommend extended culture to patients with 7 or more pronuclear-stage embryos.  For these cases we typically culture 7-8 pronuclear-stage embryos for 5 days in order to select 1-2 blastocysts for transfer.  While the extended culture period does stress the embryos more than the short-term culture, we have found that the “extended” race further facilitates selection and transfer of the most viable embryos. 

Minimize the risk of multi-fetal pregnancy

Our program continues to strive to reduce the risk of multi-fetal pregnancy while maintaining pregnancy rates/cycle.  Our goal is one healthy baby at at time.  In order to accomplish this goal our program has set forth the following embryo culture and transfer strategy:

*Only 1 embryo will be transferred if inclusion criteria met for blastocyst (day 5) single embryo transfer.

Inclusion criteria for single blastocyst embryo transfer (only 1 embryo will be replaced):

• Women or oocyte donor must be 37 years of age or younger at the time of the oocyte retrieval.
• Couples must have at least 1 embryo rated as “good” or “excellent” on Day 5 of culture to proceed with single embryo transfer.  If at least one “good” embryo is not present, then 1 or 2 embryos may be transferred.
• No previous history of a failed fresh IVF cycle (oocyte retrieval and embryo transfer) at the University of Iowa.

Inclusion criteria for double blastocyst embryo transfer(couples eligible for transfer of 2 blastocysts ifdesired):

• Women 38 years of age or older (or using an oocyte donor 38 years or older) may transfer either 1 or 2 embryos based on their desires. 
• Couples who have previously had an unsuccessful fresh IVF cycle (oocyte retrieval and embryo transfer) at the University of Iowa will have the option of transferring either 1 or 2 embryos regardless of the grading of the embryos.
• Couples of any age with no embryos rated as “good” or “excellent” on culture Day 5 will have the option of transferring 1 or 2 embryos.  We would recommend 2 embryos be transferred to optimize pregnancy rates.