What Happens During an Embryo Transfer

What happens during an embryo transfer?

On the day of transfer you arrive with a comfortably full bladder, which flattens the uterus and helps the doctor see it clearly on an abdominal ultrasound. A speculum is placed, the cervix is gently cleaned, and the embryologist loads a single embryo into a soft, thin catheter. The doctor threads that catheter through the cervical canal and releases the embryo near the top of the uterine cavity, watching the ultrasound the whole time.

No sedation or anesthesia is usually needed, because nothing is cut and the cervix is not dilated. After the release, the embryologist checks the catheter under a microscope to confirm the embryo is no longer inside it. You rest for a few minutes, then get up and go home the same day. There is nothing to recover from the way an egg retrieval requires.

Does an embryo transfer hurt?

For most people an embryo transfer is uncomfortable rather than painful, closer to a Pap smear or an IUD check than to surgery. The speculum and the full bladder are the parts people notice most. Passing the catheter through the cervix can cause a brief cramp, and occasionally a clinician uses a firmer catheter or a small instrument to steady the cervix if it is hard to navigate. most people feel no more than mild cramping, and no anesthesia is needed.

Light spotting afterward is common and comes from the catheter brushing the cervix, not from the embryo moving. Worries about the embryo 'falling out' when you stand up are not borne out by how the uterus works: the walls rest against each other and the embryo is microscopic. If the cervix is known to be difficult, some clinics do a practice 'mock' transfer in an earlier cycle so the real day goes smoothly.

What the embryo is like on transfer day

By the time of transfer, the embryo has usually grown in the lab for five days to the blastocyst stage, a ball of roughly a hundred cells, though some are transferred on day three. The embryologist assigns a grade based on its appearance and picks the best-looking one to place. Grading is a useful guide, not a guarantee: a top-grade embryo can fail and a modest one can succeed.

On a frozen transfer day the chosen embryo is thawed a few hours beforehand and checked to confirm it survived, which most good-quality embryos do. You may be shown a photo of your embryo, and many clinics give you one to keep. None of this changes the appointment itself, but it explains what the team is doing in the lab while you wait in the room.

How many embryos are transferred at once?

Most transfers today place a single embryo. Professional guidance recommends elective single embryo transfer for most patients because it keeps the chance of a healthy pregnancy high while sharply lowering the odds of twins or triplets 1Ref 1Practice Committees of ASRM and SART (2021).Guidance on the limits to the number of embryos to transfer: a committee opinion.Elective single-embryo transfer is recommended for most patients to lower multiple-gestation risk while preserving cumulative live-birth rates, especially for younger patients and euploid embryos.. Multiple pregnancy is the main avoidable risk of fertility treatment: it raises the chance of preterm birth, low birth weight, preeclampsia, and gestational diabetes 2Ref 2Practice Committee of ASRM and SART (2022).Multiple gestation associated with infertility therapy: a committee opinion.Multiple gestation is the principal avoidable risk of infertility therapy and carries higher maternal and neonatal risk, including preterm birth, low birth weight, preeclampsia, and gestational diabetes..

transferring one embryo at a time keeps the chance of a healthy singleton high while sharply lowering the risk of a multiple pregnancy.

The number that makes sense depends on your age, the embryo's stage and quality, whether it was genetically tested, and your history. A younger patient transferring a good-quality tested blastocyst has the least reason to transfer more than one. This is a conversation to have before the day itself, and a clinic's single-embryo-transfer rate is one signal of how carefully it weighs that trade-off.

Fresh or frozen transfer, and does it matter?

Whether your embryo is transferred fresh, a few days after egg retrieval, or frozen, thawed in a later cycle, mostly changes the timing and preparation, not the appointment itself. In a frozen cycle the lining is built up over a couple of weeks with medication or tracked in a natural cycle, so the frozen transfer timeline runs on its own schedule, separate from the retrieval.

For success, the honest answer is that it depends on who you are. In ovulatory women without PCOS, large randomized trials found no significant difference in live-birth rates between frozen and fresh transfer 3Ref 3Shi Y, et al. (2018).Transfer of Fresh versus Frozen Embryos in Ovulatory Women.In ovulatory women without PCOS, live-birth rates did not differ significantly between frozen and fresh embryo transfer.. In women with PCOS, a frozen transfer did better: a higher first-transfer live-birth rate, 49.3% vs 42.0%, with less ovarian hyperstimulation 4Ref 4Chen ZJ, et al. (2016).Fresh versus Frozen Embryos for Infertility in the Polycystic Ovary Syndrome.In women with PCOS, frozen-embryo transfer produced a higher first-transfer live-birth rate than fresh transfer (49.3% vs 42.0%), with lower ovarian hyperstimulation.. So freezing everything is not automatically better. It is a targeted choice, and the frozen embryo transfer vs fresh transfer decision is one to make with your clinic based on your diagnosis.

What the two-week wait can and cannot tell you

After the transfer comes the wait until a blood pregnancy test, usually about nine to twelve days later. Symptoms in that window, such as cramping, spotting, sore breasts, or fatigue, are unreliable, because the progesterone support given after most transfers produces the same feelings whether or not an embryo has implanted. A blood test measuring hCG is the only real answer.

It helps to set expectations from national data rather than a single clinic's advertisement. Outcomes are reported by age band and by cycle, and per-transfer live-birth rates fall as age rises 5Ref 5Society for Assisted Reproductive Technology (SART) (2024).National Summary Report (SART CORS Online).US national IVF outcomes are reported by patient age band and by cycle, and per-transfer live-birth rates decline as age rises.. One transfer is one attempt, not the whole of your odds; many people who succeed do so over more than one transfer from a single egg retrieval. Whether a rate is quoted per transfer, per retrieval, or per cycle changes the number a great deal.

Add-ons and extra costs around the transfer

A transfer can arrive bundled with optional extras, and it is worth knowing which ones the evidence supports. Genetic testing of embryos, PGT-A, is the most common: it is often sold as a way to pick the embryo most likely to implant, but its value as a routine screen for everyone has not been demonstrated, and recent multicenter trials found similar overall pregnancy outcomes with and without it 6Ref 6Practice Committees of ASRM and SART (2024).The use of preimplantation genetic testing for aneuploidy: a committee opinion.The value of PGT-A as a routine screen for all IVF patients has not been demonstrated; recent multicenter trials found similar overall pregnancy outcomes with and without it.. Whether PGT-A actually improves IVF success is a fair question to put to your clinic.

Frozen transfers also carry their own line items, including lining medications, monitoring scans, and thaw and storage fees, so the FET cost is worth asking about in advance rather than discovering it on the invoice. None of these add-ons changes what the transfer appointment feels like; they change the bill and, sometimes, the timeline. A standard cycle without unproven add-ons is often the better value.