What is the frozen embryo transfer protocol for a surrogate?

What is a medicated FET cycle, and why do clinics use it for surrogates?

A frozen embryo transfer (FET) cycle prepares a uterus to receive an embryo that was created and frozen earlier. In a medicated FET, the clinic replaces the surrogate's natural hormone cycle with medications: estrogen to build the uterine lining, then progesterone to make it receptive. Some clinics first suppress her own cycle with Lupron.

For a gestational surrogate, the whole medicated protocol runs about 4 to 6 weeks from the start of medications to the pregnancy test, longer when Lupron suppression comes first.

Clinics use medicated cycles for most surrogates for three practical reasons:

1. Control of timing. Your embryos are frozen and waiting. In a medicated cycle the clinic, not the surrogate's ovulation, sets the transfer date. That matters when she is traveling to a clinic in another city or state.
2. Predictable monitoring. A medicated cycle needs fewer monitoring visits at precise times than a natural one, which is easier when monitoring happens at a clinic near her home.
3. Planning around two families. The surrogate has her own children, work and household. A transfer date set weeks in advance lets her arrange childcare and time off.

The surrogate does not take stimulation drugs. She is not producing eggs, so she skips the injections and trigger shot an IVF patient takes. Her medications only prepare the uterus.

Before the real cycle, some clinics run a mock cycle: the same medications without a transfer, to see how the surrogate's lining responds.

What is the day-by-day medication calendar?

Every clinic writes its own calendar, and your surrogate's calendar will come from your clinic. The pattern below is typical for a day 5 blastocyst transfer.

Typical doses at many clinics: Lupron 10 units (0.1 milliliter) a day under the skin, often reduced once estrogen starts; oral estradiol 4 to 8 milligrams a day in divided doses, or the equivalent by patch or injection; progesterone in oil 50 milligrams (1 milliliter) a day by intramuscular injection. Doses vary by clinic and by the surrogate's response. The clinic sets them.

The progesterone start changes with the embryo's age. A day 6 blastocyst usually means progesterone starts 6 days before transfer. The clinic times it to match.

What lining thickness and pattern does the clinic want?

At the lining check, the clinic measures the endometrium, the inner lining of the uterus, on a transvaginal ultrasound. Most clinics look for two things:

• Thickness of about 7 millimeters or more. A lining in this range is generally considered ready. Many linings measure well above it.
• A trilaminar pattern, sometimes called a triple-line pattern: three distinct lines on the ultrasound, which shows the lining has responded to estrogen as expected.

The clinic also checks hormone levels in her blood to confirm the estrogen is being absorbed.

If the lining is thin, the clinic usually extends estrogen, raises the dose or changes the route, for example from pills to patches or injections, and checks again. Occasionally a cycle is canceled and restarted. Thresholds vary by clinic. The clinic decides when the lining is ready.

What happens at the transfer appointment?

The surrogate travels to your fertility clinic. Your clinic's embryology lab thaws the embryo shortly before the procedure and confirms it survived the thaw.

The procedure takes about 10 minutes and needs no anesthesia. The surrogate usually arrives with a comfortably full bladder, which tilts the uterus into a better position and makes the ultrasound image clearer. The physician places a speculum, as for a Pap smear, and passes a thin, soft catheter through the cervix. Using abdominal ultrasound to guide it, the physician releases the embryo into the upper part of the uterus. The embryologist then checks the catheter under a microscope to confirm the embryo is no longer in it.

It does not hurt. Most surrogates describe mild pressure from the full bladder. She rests briefly and is free to go. Most return to light activity the same day.

You may be able to attend in person or by video, if the clinic and the surrogate agree. One embryo is transferred in nearly all PLS journeys.

What should the surrogate do in the days after transfer?

Continue every medication exactly on schedule. That matters more than anything else in this window, because in a medicated cycle her body is not making enough progesterone on its own to support a pregnancy.

Bed rest is not needed. Studies show bed rest does not improve outcomes. Clinics usually advise:

• Avoiding strenuous exercise and heavy lifting for a few days.
• Light walking and normal daily activity are fine.
• Checking with the clinic nurse before taking any over-the-counter medication.
• Calling the clinic for heavy bleeding, fever, severe pain or anything that worries her.

Travel home is usually the same day or the next, depending on distance. Light spotting or mild cramping can happen and is common. The two-week wait is hard on everyone. Many clinics discourage home pregnancy tests in this window, because an early result can mislead in either direction.

When is the pregnancy test, and when do medications stop?

The pregnancy test is a beta hCG blood test 9 to 11 days after transfer. It measures human chorionic gonadotropin, the hormone an implanted embryo produces. Many clinics repeat it to see the trend. The beta hCG page explains what the numbers mean.

If the test is positive, estrogen and progesterone continue until about 10 weeks of pregnancy, when the placenta makes enough progesterone on its own. The clinic then tapers the medications on its own schedule. After early ultrasounds, the clinic releases the surrogate to her own obstetrician.

If the test is negative, the clinic tells her when to stop medications, and her period follows. Your clinic, you and the surrogate then plan the next step.

Medication side effects range from Lupron hot flashes to injection-site soreness. The injections themselves are explained on the progesterone in oil page.

What is a natural or modified natural FET, and when is it used?

A natural FET uses the surrogate's own ovulation instead of medications to prepare the lining. The clinic tracks her cycle with ultrasounds and blood or urine tests, identifies when she ovulates, and times the transfer to it.

A modified natural FET follows her own cycle but adds a trigger shot to set the exact ovulation day, and often adds progesterone support after transfer.

These approaches use fewer medications. The trade-off is timing. The transfer date depends on when she ovulates, which can shift by days and requires more frequent monitoring. For a surrogate who must travel to your clinic, that uncertainty is harder to plan around. Some clinics use natural or modified natural cycles for surrogates with regular cycles who live near the clinic, or after a medicated cycle did not produce a good lining. The clinic decides which protocol fits.

What does PLS coordinate during the cycle, including travel and the $1,000 transfer fee?

Nothing medical starts until the gestational carrier agreement is signed and you have funded independent escrow: $10,000 at match and the balance before medications start. Once that is done, PLS coordinates the cycle around the surrogate's life and your clinic's calendar.

• The calendar. Your clinic writes the protocol. PLS makes sure the surrogate, her monitoring clinic and you all have the same dates.
• Local monitoring. Blood work and ultrasounds happen at a clinic near the surrogate's home, billed through escrow, so she is not traveling for every check.
• Travel. PLS arranges the surrogate's travel to your clinic for the transfer. Travel is paid from escrow, not by the surrogate.
• Compensation tied to the cycle. PLS surrogates receive a $500 medication start fee when injections begin and a $1,000 transfer fee for each embryo transfer, both paid from escrow. PLS surrogates also receive a $300 monthly allowance. Lost wages are reimbursed under the agreement.
• People who have done it. Case managers Natalie Gaudio-Fricano and Jenni Symons carry the active matches, and both have been surrogates themselves. Jan Telman Berman manages national and international cycles.

This page gives general information about FET protocols. It is not medical advice. Your clinic sets the protocol and decides when to transfer. If you are thinking about becoming a surrogate, start with the surrogate compensation page.

Sources

• ASRM (American Society for Reproductive Medicine), guidance on frozen embryo transfer and on practices using gestational carriers. https://www.asrm.org/
• SART (Society for Assisted Reproductive Technology), patient information on frozen embryo transfer. https://www.sart.org/
• CDC (Centers for Disease Control and Prevention), national assisted reproductive technology data. https://www.cdc.gov/art/