In vitro fertilization (IVF) is how an embryo is created for almost every gestational surrogacy journey. Eggs are combined with sperm in a fertility clinic's laboratory, the resulting embryos are grown for several days, and one healthy embryo is then transferred into your gestational carrier's uterus. In a gestational surrogacy arrangement, the carrier has no genetic relationship to the child - the embryo is made from the intended parents' or donors' eggs and sperm - which is the reason surrogacy relies on IVF rather than on artificial insemination. That single fact shapes everything that follows: the medical steps, who provides which cells, why usually only one embryo is placed at a time, and what happens if a transfer doesn't take.
This page walks through the whole medical picture at a level intended parents actually ask about. For the detailed clinical walkthrough of each step, see the step-by-step medical process for IVF; this hub is the overview that ties it to your journey.
What is IVF, in plain terms?
IVF means fertilizing an egg with sperm *outside* the body, in a laboratory, and then growing the resulting embryo before it is placed in a uterus. "In vitro" is Latin for "in glass" - it simply describes that fertilization happens in the lab rather than inside a person. IVF is the most common and established form of assisted reproductive technology (ART), and it is the foundation that makes gestational surrogacy possible, because it lets an embryo be created from one set of people and carried by another.
In a surrogacy journey, the eggs come from the intended mother or an egg donor, and the sperm comes from the intended father or a sperm donor. The embryo that results belongs to the Intended Parents who are creating the embryos - not to the gestational carrier who carries the pregnancy.
How does IVF work, step by step?
A full IVF cycle moves through a predictable sequence. Each of these steps is described in clinical detail in the surrogacy process: medical steps for IVF; here is the shape of it so you can see how the pieces connect.
1. Ovarian stimulation. The person providing the eggs - the intended mother or an egg donor - takes injectable fertility medications (gonadotropins) for roughly a week and a half to encourage the ovaries to mature several eggs at once instead of the single egg a natural cycle produces. Per the American Society for Reproductive Medicine (ASRM), the stimulation phase typically lasts 8 to 14 days.
2. Monitoring. The clinic tracks progress with ultrasounds and blood tests to follow the growth of the ovarian follicles and hormone levels, adjusting medication as needed.
3. Trigger and egg retrieval. When the follicles are ready, a "trigger" injection completes the eggs' final maturation, and the eggs are collected about a day and a half later. ASRM describes egg retrieval as a procedure in which the doctor uses ultrasound through the vagina to guide a thin needle into each follicle to retrieve the eggs, roughly 36 hours after the trigger injection. It is a short procedure done under sedation, not major surgery. 4. Fertilization. In the lab, the eggs are fertilized with sperm. ASRM describes two standard approaches: conventional insemination, where eggs are placed in a dish with thousands of sperm, and intracytoplasmic sperm injection (ICSI), where a single sperm is injected directly into each egg.
5. Embryo growth. Fertilized eggs are grown in the lab for several days. An embryo reaches the blastocyst stage - a more developed embryo of roughly a hundred cells - at about day five or six of growth, which is a common point to transfer or freeze. (An embryo on day three is at the earlier "cleavage" stage of roughly eight cells, per the Society for Assisted Reproductive Technology's review of blastocyst versus cleavage-stage transfer00402-8/fulltext).)
6. Embryo transfer. A healthy embryo is placed into the carrier's uterus through a thin catheter, bypassing the fallopian tubes. Any additional good-quality embryos can be frozen for a future transfer.
The whole active cycle - from the start of stimulation to the embryo transfer - generally spans a few weeks, though frozen embryos are often transferred in a separate cycle scheduled later around the carrier's body, rather than on the same timeline as the retrieval.
Why does gestational surrogacy use IVF instead of artificial insemination?
Because the whole point of gestational surrogacy is that the carrier is *not* the genetic mother - and only IVF can make that true. ASRM defines a gestational carrier as someone who carries a pregnancy created through IVF using an embryo with which the carrier has no genetic relationship. The embryo is made from the intended parents' or donors' eggs and sperm and then transferred to her.
Artificial insemination (intrauterine insemination, or IUI) works differently: sperm is placed directly into a woman's uterus so it can fertilize *her own* egg, inside her body. If a surrogacy journey used insemination, the carrier's own egg would be fertilized - which would make her the genetic mother. That is traditional (or "genetic") surrogacy, and ASRM notes it does not involve IVF, relies on the carrier's own egg, and is uncommon in clinical practice today, in part because a genetic link to the carrier raises harder legal and ethical questions. Gestational surrogacy, built on IVF, keeps parentage clear from the start - which is exactly why it is the model modern surrogacy law is written around, and the model WSS works within.
What is the difference between IVF and IUI?
The short version: IUI puts sperm into the uterus and lets fertilization happen naturally inside the body; IVF fertilizes the egg in a laboratory and then places the resulting embryo into the uterus. IUI is a simpler, lower-intensity treatment often tried first for certain kinds of infertility, and it is less involved than a full IVF cycle. IVF is more involved but does far more: it allows the use of donor eggs or donor sperm, it makes embryo freezing and genetic testing possible, and - critically for surrogacy - it separates the genetic parents from the person carrying the pregnancy. For building a family through a gestational carrier, IVF is not just the better option; it is the only one that produces a gestational (non-genetic) carrier.
How is the embryo transferred to your surrogate, and how does she prepare?
The transfer itself is quick and does not require surgery or sedation. In the days and weeks beforehand, the carrier's uterus is prepared with hormone medication - typically estrogen to build the uterine lining, then progesterone to make the lining receptive to an embryo - so that her cycle is timed precisely to the embryo's stage of development. On transfer day, the doctor guides a thin, soft catheter through the cervix and releases the embryo into the uterus, usually while watching on ultrasound. The carrier rests briefly and generally returns to normal, non-strenuous activity soon after.
Progesterone support does not stop at the transfer. It is standard practice to continue progesterone into early pregnancy - commonly for the first eight to ten weeks - until the placenta takes over hormone production, which is why your carrier may stay on medication well past a positive test. A pregnancy blood test that measures the hormone hCG is typically done about 9 to 14 days after the transfer; that blood test, not a home test, is how the clinic confirms whether the embryo has implanted.
The number of embryos placed is one of the most important decisions in this step - and it is covered next, because for a surrogate it is usually one. For how this connects to the rest of the medical timeline, see the surrogacy process: medical steps for IVF.
Why is usually only one embryo transferred to a surrogate?
Because transferring a single embryo is the safest choice for the woman carrying your child, and the major reproductive medicine bodies are unusually direct about it in surrogacy specifically. Placing two embryos raises the chance of twins, and a twin pregnancy carries meaningfully higher risks - for both the babies and the carrier - than a single pregnancy. ASRM's guidance on the number of embryos to transfer and its recommendations for practices using gestational carriers both point toward single embryo transfer as the strongly preferred approach in gestational carrier cycles, precisely because of the added risk that multiples pose to the carrier.
Because embryo freezing and lab selection have improved, transferring one good embryo at a time no longer means giving up much in the way of success - and it protects the surrogate. This is also why the question of multiples, and the difficult conversations that can follow, is one intended parents and carriers agree on in advance; WSS covers that in why intended parents and surrogates discuss selective reduction. Protecting the health of the woman who carries for you is central to how a responsible journey is run - see more on the health and safety of the women who carry.
What happens if an embryo transfer doesn't work?
Sometimes a transfer doesn't result in a pregnancy, and it is worth knowing in advance that this is a normal part of the process rather than a sign that the journey has failed. Even a healthy-looking embryo transferred to a proven, screened carrier may not implant, and there are a few well-understood reasons why.
The most common single factor is the embryo itself. Many embryos carry chromosomal abnormalities that prevent them from implanting or developing, which is why some intended parents choose genetic testing of embryos (PGT-A) before transfer to select a chromosomally normal one. The other major factor is the uterine environment and the precise timing of the window in which the lining will accept an embryo. Medical reviews of recurrent implantation failure describe embryo chromosomal status and endometrial (uterine-lining) receptivity as leading contributors, among others. A gestational carrier is chosen in part for a proven history of healthy pregnancy, which helps - but it does not make any single transfer a certainty.
If a transfer doesn't take, the usual next step is to review what happened with your clinic, transfer another frozen embryo if one is available, or adjust the protocol first. Many families who conceive do so on a second or later transfer, so a single negative result is not the end of the road. The number of transfer attempts included in a surrogacy arrangement is set out in your agreement with the carrier - see the gestational carrier contract - and your case manager and legal team walk you through those terms before you begin. Usually the Surrogacy Agreement will provide for three embryos transfers.
Where does IVF fit in your overall surrogacy journey?
IVF is one medical chapter inside a longer journey that also includes matching with a carrier, legal contracts and parentage work, the pregnancy itself, and delivery. The clinical steps on this page are handled by your fertility clinic; your WSS case manager coordinates around them and stays with you throughout - the same person from your first conversation through delivery, so nothing is handed off between phases. To see how the medical process sits alongside everything else, read about the full intended-parent journey, and for what it all costs, see what a full surrogacy journey costs. You can also read about the surrogate's side of the journey to understand what your carrier experiences.
Frequently asked questions
How long does one IVF cycle take?
The active stimulation phase runs about 8 to 14 days before egg retrieval, and fertilization and embryo growth add several more days. When a frozen embryo is used - common in surrogacy - the transfer is usually scheduled in a separate cycle timed to the carrier, so the retrieval and the transfer may be weeks or months apart.
Does the surrogate's own egg get used?
No. In gestational surrogacy the embryo is created through IVF from the intended parents' or donors' eggs and sperm, and the carrier has no genetic relationship to the child. Using the carrier's own egg would be traditional surrogacy, a different and now-uncommon arrangement that WSS's gestational model does not use.
How many embryos are transferred to a surrogate?
Usually one. Single embryo transfer is the strongly preferred approach in gestational carrier cycles because a twin pregnancy adds real risk for the carrier, and improved embryo selection means one embryo at a time no longer means a large drop in success.
When will we know whether the transfer worked?
A pregnancy blood test measuring hCG is generally done about 9 to 14 days after the transfer. That clinic blood test, not a home test, is the reliable confirmation of whether the embryo implanted.
What if the first transfer doesn't result in a pregnancy?
It is common and not a dead end. The usual reasons are embryo chromosomal factors or the uterine environment, per reviews of implantation failure, and the next step is typically to transfer another embryo or adjust the plan with your clinic. Many families succeed on a later transfer.
Is IVF painful for the surrogate?
The embryo transfer is a brief, non-surgical procedure and is generally well tolerated. Your carrier does take hormone medication to prepare her uterus, which can have side effects, and she receives specific aftercare instructions from the clinic - including which symptoms warrant a call to the medical team. Her comfort and safety are managed by the fertility clinic and supported by her WSS case manager throughout.
Ready to talk it through?
If you are trying to understand how the medical process would work for your family, the clearest next step is a conversation with someone who has guided many families through it.
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