Conventional IVF Gestational Surrogacy involves the transfer of one or more embryos made by the fertilization of eggs from an egg provider (the infertile woman or a designated egg donor) and from sperm of her partner (or a designated sperm donor) into the uterus of a Gestational Carrier (carrier/surrogate). Here, the carrier provides a host womb but does not contribute genetically to the baby. While ethical, moral, and medico‑legal issues still apply, IVF surrogacy appears to have gained more social acceptance than classic surrogacy.

Candidates for IVF Gestational Surrogacy can be divided into two groups: (1) women born without a uterus or who because of uterine surgery (hysterectomy) or disease are not capable of carrying a pregnancy to full term; and (2) women who have been advised against undertaking a pregnancy because of systemic illnesses, such as diabetes, heart disease, hypertension, or certain malignant conditions.

Conventional IVF with Gestational Surrogacy is very complex. It begins with an intensive phase of surrogate (carrier) recruitment and selection, followed by the execution of a binding legal contract between the carrier and the prospective parents. Then follows painstaking coordination of the respective timetables of both parties, followed by the egg provider (usually a genetic parent) and the carrier both having to take a birth control pill (BCP) for varying lengths of time. Upon discontinuing the BCP, both parties would menstruate at virtually the same time. This ensures that the initiation of the egg provider’s cycle of controlled ovarian stimulation (COS) will coincide with the carrier commencing hormonal supplementation to prepare her uterus to receive freshly transferred embryo(s) at the precise stage of optimal endometrial receptivity (i.e. the “window of implantation”).

This process is not only complex, but is almost always inconvenient as well. It requires careful synchronization of the cycles of two different parties. Then there is the ever-present possibility that having remitted a large amount of (often upfront and often non-refundable ) money to secure a carrier, unforeseen events such as ovarian hyperstimulation, failed fertilization and/or arrested embryo development could inadvertently disrupt the process and result in cancellation of the cycle – leaving the prospective parents “high and dry” with an enormous financial and emotional burden.

So, how can we simplify the entire Gestational Surrogacy process, making it much more efficient, convenient, tolerable, less risky (and also less expensive) without compromising the chance of success? The answer lies in separating the cycle of egg retrieval from the embryo transfer, which would be performed in a subsequent cycle. The embryos/blastocysts generated following fertilization of the provider’s eggs, are vitrified and frozen (cryobanked) for dispensation to the carrier in a subsequent cycle. Such separation of the egg retrieval and the transfer cycle is referred to as “Staggered In Vitro Fertilization” (St-IVF).

Combining St-IVF with CGH for Gestational Surrogacy: A few years ago, SIRM introduced an embryo selection technique known as Comparative Genomic Hybridization (CGH) into the clinical IVF arena. CGH identifies embryos that have a “normal” chromosomal composition. Each such “competent” embryo, upon being transferred to a receptive uterus, yields better than a 60% chance of a live birth. Since it generally takes several weeks to perform and get results from a CGH analysis, it is not possible to transfer CGH-tested embryos in the same cycle that they are created. They must be frozen and stored (cryobanked) for subsequent transfer in a later cycle.

The recent introduction of ultra-rapid embryo cryopreservation (vitrification) has all but eliminated the prior risk that the freezing process would destroy or damage embryos and compromise success following their transfer to the uterus.

So now, by using CGH embryo selection, we can identify “competent” embryos and then through vitrification we can safely freeze/store these for transfer at a later date. Using this St-IVF approach we can now profoundly simplify IVF Gestational Surrogacy, reducing the financial and emotional burden and at the same time rendering it far more efficient and convenient.

The combination of St-IVF with CGH for Gestational Surrogacy requires four (4) distinct stages:

The 1st stage includes the egg provider undergoing ovarian stimulation, egg retrieval (ER), egg fertilization, embryo biopsy for CGH analysis, and finally, embryo vitrification (freezing) and storage.

The 2nd stage involves confirming that at least one (1) CGH-normal (“competent”) embryo has been secured for subsequent transfer to a Gestational Carrier.

In the 3rd stage, the prospective parents select the carrier of choice, and enter into a binding contractual relationship with her. The carrier then undergoes thorough medical and psychological screening to prepare her for the process ahead.

The 4th stage involves hormonally preparing the carrier’s uterus for a standard Frozen Embryo Transfer (FET), electively thawing/ warming of one or two CGH-normal frozen embryo(s) and then transferring these to the surrogate’s uterus.

Clearly the addition of CGH to the IVF surrogacy equation, while highly beneficial, is not an essential part of the Staggered IVF approach. It adds additional costs, but in return yields improved efficiency (see below).

Incorporating Staggered IVF into the Gestational Surrogacy equation has a distinct financial benefit as well; by ensuring that the egg retrieval cycle on the provider and the FET to the Gestational Surrogate are separated in time, it allows for the egg retrieval to be performed without the prospective parents having to make the significant financial and emotional commitment involved in recruiting and securing a carrier before confidently knowing that the FET will indeed go forward.

It also avoids the complexities associated with first having to synchronize the menstrual cycles of the egg provider and carrier. This makes the entire process infinitely more convenient and tolerable for all concerned. In fact, with Staggered IVF, the carrier does not even need to be present at the IVF center for the 1st and 2nd stages. As soon as test results are available, the FET on the carrier can be conveniently scheduled, and in cases where CGH embryo selection is incorporated, there is sufficient time for all laboratory testing to be completed well in advance of FET. In fact, the carrier is not required to spend more than 6 days in total at the IVF center.

Simply stated, the incorporation of Staggered IVF with Gestational Surrogacy eliminates unnecessary financial risk and unanticipated disappointments, simplifies the process, improves convenience, and minimizes stress. And when CGH embryo selection is incorporated, the success rate per embryo transferred is vastly improved (to greater than 60%), along with the ability to predict a favorable outcome following elective FET. At the same time, the use of CGH-selected embryos reduces the chance of miscarriage and chromosomal birth defects. Finally, because the transfer of each chromosomally (CGH) normal embryo is far more likely to propagate a viable pregnancy, there is no need to transfer multiple embryos at a time, thus minimizing the risk of high-order multiple births.