Our IVF Success Rates with Day 5 Blastocyst Transfers

Pregnancy rates with blastocyst culture and transfer

Pregnancy success rates with blastocyst transfer are potentially confusing. Because almost all clinics that use extended culture and blastocyst transfer are selective in choosing patients that will be eligible for this procedure, we should expect that pregnancy rates would be higher in this population as compared to the rates seen in "unselected" patients.

This does not necessarily mean that having a blastocyst transfer increases a couples chance for pregnancy. It means that (for example) if we select patients for blastocyst transfer that are younger and have more embryos that look better under the microscope (better embryo quality) - we should have higher success rates - because we already know that those patients are more likely to have success - regardless of whether we transfer the embryos on day 3 or day 5.

In my opinion, the greatest benefit of blastocyst transfer is to reduce the risk of multiple pregnancy by transferring fewer embryos of higher quality. We have had a very low percentage of triplet (or higher order) pregnancies from blastocyst transfer. The rate of triplets with blast transfers at our IVF center has been about 2% of pregnancies. These triplets have almost always been the result of "identical twin" splitting of an embryo - 2 transferred and 3 implanted - after one of the embryos split into 2.

Having said all of that, shown below are the live birth success rates for blastocyst transfer cases at our IVF clinic:

January 1, 2003 through December 31, 2006

Live birth rates per transfer for day 2 and 3 "cleavage stage" transfers versus Day 5 and Day 6 blastocyst transfers
This represents a total of 1003 embryo transfer procedures
We rarely do day 2 or day 6 embryo transfers, but those are included here to be complete
 

In this same time period, 40 patients (total for all age groups) had an egg retrieval procedure but had no embryo for transfer (3.8% of egg retrievals)
Since the above statistics are "per embryo transfer", the patients without a transfer are not represented in this data

Regarding day 6 blastocyst transfer statistics

In the early years of blastocyst transfer in our IVF program we sometimes looked at the embryos early on day 5 and had some of the patients with slower embryo development to come in early on day 6 for their blast transfer. The thinking was that it might be better to let those slower embryos develop and expand more in the dish before choosing the best 1 or 2 for transfer. As far as comparing day 5 and day 6 blastocyst transfers, success rate statistics for day 6 blastocyst transfers were somewhat lower than for day 5. This is likely because some of those embryos that are "slower" on day 5 are weaker, poorer quality embryos.

However, blastocyst formation on day 6 is not necessarily an indication of a problem. Morulas that expanded and made blasts on day 6 and went on to make babies after day 6 transfers were perfectly strong and healthy - just slow starters. Remember the story about the tortoise and the hare?

This graph represents the same data as shown in the tables above
Blue columns are for day 3 embryo transfers
Red are all transfers
Yellow are day 5 and day 6 embryo transfers

See our overall pregnancy and live birth rates

Photo of an IVF blastocyst embryo starting to hatch from its shell  - lower right of picture
This blastocyst is grade 5AA
After hatching, the embryo can invade and implant in the uterine lining
Photo taken a few minutes prior to embryo transfer