Since gestational surrogacy relies upon undergoing IVF, we suggest you consult our detailed course on the subject, and the important decisions you’ll face.
If you intend to use donor eggs in conjunction with surrogacy, you may want to review our IVF with Donor Eggs course and a specific lesson on tailoring IVF for cycles using donor eggs.
As for tailoring the cycle for considerations related to surrogacy, there may be a few subjects to consider. It’s important that you discuss any medical decision with your doctor at length and with data they think is most relevant to your circumstances.
During IVF, once a laboratory fertilizes the retrieved eggs, they have the decision to grow embryos to the “cleavage” stage (often reached on “Day 3”) or the “blastocyst” stage (often reached on “Day 5” or “Day 6”) before trying a transfer.
Embryos that have survived to the blastocyst stage are more likely to lead to a live birth, as you can see below. Unless the intended parents have issues making embryos that can reach blastocyst, or a clinic’s not confident in its abilities to grow blastocysts, allowing embryos to grow to this stage may be preferable. To learn more about the importance of the laboratory and how to gauge its abilities, see our course here.
For one, using a blastocyst stage embryo improves the odds the doctor selects an embryo that will lead to a successful transfer. Second, it preserves the ability to have the embryo tested (which we’ll cover next), and finally if embryos need to be frozen for a later date (this flexibility can be invaluable when trying to line up a gestational carrier), they’re more likely to survive the process as heartier blastocysts, as you can see from multiple studies below. To learn more, you can see our dedicated lesson here.
If embryos are grown to the blastocyst stage, they can be biopsied (where a few cells are removed and tested) to ascertain if an embryo has the right number of chromosomes. In effect, this testing is a tool to help doctors select embryos for transfer that are more likely to lead to a delivery.
Such testing, known as Preimplantation Genetic Testing for Aneuploidy (PGT-A) should be done on blastocysts rather than cleavage stage embryos because the biopsy is less likely to have a negative effect, as you can see below.
Credible experts disagree on when PGT-A is most useful and below we provide a catalogue of the trade-offs.
In the case of an IVF cycle using a gestational carrier, PGT-A is likely more warranted given the cost and effort spent to line up the process and the seemingly larger risk (e.g. a carrier will stop the process) should the first few transfers not result in a delivery.
A secondary byproduct of using PGT-A to test embryos is that doctors, intended parents, and gestational carriers likely have more faith in each embryo that passes PGT-A and are more open to transferring one embryo at a time, as you can see below in the evidence from a single center. To learn more about PGT-A, the process and the trade-offs, see our lesson here.
As we’ve alluded to repeatedly, it’s tempting for intended parents to want to transfer multiple embryos in a single transfer. Simply stated, it raises the odds that transfer works.
However, if one is willing to undergo (and pay for) a second transfer (if it’s even needed), the odds of success are basically the same.
If doctors are selecting only blastocyst embryos that have passed PGT-A testing, the odds are higher they’ll select a better quality embryo thereby reducing the need for a second transfer.
What’s gained by deploying this “single embryo transfer” strategy is a reduction in risk of a multiple gestation pregnancy, which, as we’ve shown, creates risk for the carrier and offspring.
In light of the circumstances, this can be a complex decision, and you can see more detail on the matter at our dedicated course here.
The embryo transfer is an art and the spectrum of doctors abilities are wide-ranging. Even within the same clinic, doctors have varied track records. Below you’ll see how 11 different transferring doctors at one well regarded clinic perform. The best performer has a 16% absolute higher percentage Live Birth Rate (67% vs. 51%) than the least successful performer.
Roughly 90% of clinics report they regularly track this data, and most tell us these discrepancies are commonplace. Given the import of the transfer, and the cost and complexity required to get to this point, you may want to consider asking your clinic if one of the doctors with the highest transfer rates of success can be assigned to your transfer.