Hormones Surrogates Take: A Complete Guide to the Embryo Transfer Protocol
When you start researching surrogacy, you will quickly run into terms like “hormonal stimulation,” “fertility medications,” and “IVF protocol” — and it is not always clear which parts apply to you as a surrogate. The short answer: you do not go through ovarian stimulation or egg retrieval. Those steps belong to the person providing the eggs — the intended mother or an egg donor. Your hormonal protocol is different, and simpler.
The hormones surrogates take serve one purpose: preparing your uterus to receive and support the embryo. At Physician’s Surrogacy, the only surrogacy agency in the United States managed by practicing OB/GYNs (obstetrician-gynecologists), our physicians oversee this process directly — reviewing your medications, monitoring your response, and communicating peer-to-peer with the fertility clinic’s reproductive endocrinologist when questions arise.
This guide covers exactly what the surrogate hormone protocol involves — which medications, what they do, what side effects to expect, and what the full timeline looks like from preparation through pregnancy confirmation.
Key Takeaways
Why Surrogates Need Hormonal Preparation
In a natural pregnancy, your body’s own hormonal cycle prepares the uterine lining every month. Estrogen builds the lining, progesterone stabilizes it, and if a fertilized egg arrives at the right moment, it has a ready environment.
In a frozen embryo transfer (FET) cycle — how most surrogacy transfers work — the fertility clinic must control that timing precisely. The clinic cannot rely on your natural cycle to produce the right conditions on the exact day the embryo is ready. So the clinic removes your natural cycle from the equation and creates the right uterine environment artificially, using estrogen and progesterone on a controlled schedule that syncs with the embryo.
That is the entire purpose of the surrogate hormone protocol. It is not the intense process that ovarian stimulation involves. It is targeted preparation for one specific goal.
Phase 1: Suppression — Not Always Required
Some fertility clinics begin the surrogate hormone protocol with a suppression phase to regulate your cycle before building it back up on their schedule. This is common in certain protocols but not universal — your clinic may or may not include this step.
Do Birth Control Pills Count as Part of the Surrogate Protocol?
Birth control pills are the most common suppression method. You take oral contraceptive pills for 2–4 weeks before estrogen begins. The pills quiet your natural hormonal fluctuations so the clinic can start estrogen at a predictable baseline. Side effects during this phase mirror standard birth control: possible mood changes, lig
t spotting, breast tenderness, or mild nausea. Most surrogates tolerate this phase without major disruption.
What Is Lupron Used for in Surrogacy?
Some protocols use Lupron (leuprolide acetate) — a GnRH agonist — instead of or alongside birth control. Lupron suppresses your pituitary gland’s hormone production, putting your ovaries in a temporary resting state. Clinics administer it as a daily subcutaneous injection, typically in the abdomen.
Side effects can include hot flashes, headaches, and mood shifts — essentially mild, temporary menopause-like symptoms that resolve once you stop taking it. Not all clinics use Lupron for FET cycles; its use depends on the specific protocol the reproductive endocrinologist (RE) designs for your case.
Phase 2: Estrogen — Building the Uterine Lining
Once suppression (if used) is complete, estrogen begins. This phase develops your uterine lining — called the endometrium — to the right thickness and texture to receive the embryo.
The endometrium must reach a minimum thickness, typically at least 7–8mm, for the transfer to proceed. Estrogen drives that growth and also affects the lining’s receptivity.
The fertility clinic monitors your lining with transvaginal ultrasound during this phase, usually one or two times, to confirm it is developing properly before moving forward.
How Is Estrogen Taken During the Surrogate Protocol?
Estrogen comes in several forms, and different clinics prefer different delivery methods. Your clinic will specify which form and dose they prefer. The estrogen phase typically lasts 2–3 weeks.
- Oral tablets. Taken by mouth, typically 2–3 times per day. The most straightforward option.
- Patches. Adhesive patches applied to the skin and changed every few days. They deliver a steady dose without the peaks and troughs of oral dosing.
- Injections. Estradiol valerate given as an intramuscular injection every few days. Less common but used in some protocols.
- Vaginal suppositories. Less commonly used for estrogen alone, but some protocols combine delivery methods.
Most surrogates find estrogen easy to tolerate. Common side effects include bloating, breast tenderness or fullness, mild nausea, headaches, and mood changes — some women feel more emotional, others notice no difference at all. Light spotting is more common with vaginal forms.
These effects are temporary and typically ease as your body adjusts. If you experience severe nausea or headaches that do not respond to over-the-counter relief, contact your coordinator or care team.
Phase 3: Progesterone — Stabilizing the Lining for Transfer
Once your lining reaches the target thickness, progesterone is added. This is the hormone that most surrogates have the most to say about — it is effective, it is necessary, and it comes with side effects worth knowing about upfront.
In a natural cycle, progesterone rises after ovulation and shifts the lining into a receptive state — ready to support an implanting embryo. In a FET cycle, the clinic adds progesterone 5–7 days before the scheduled embryo transfer, mimicking the natural post-ovulation window. The embryo transfers into a lining that is in exactly the right developmental stage.
If the transfer results in pregnancy, progesterone continues for several weeks — typically through 10–12 weeks, when the placenta takes over its own progesterone production.
What Are Progesterone in Oil (PIO) Injections Like?
Progesterone is most commonly administered as an intramuscular injection — progesterone in oil (PIO) — in the upper outer quadrant of the buttocks. The oil base, usually sesame, olive, or ethyl oleate, makes the injection effective and long-lasting, but it also makes the injection site sore afterward.
Warm the oil before injecting — hold the syringe in your hands or run it under warm water for a minute. Warmer oil flows more easily and causes less discomfort. Inject slowly (30 seconds or more per injection), massage the site firmly for 1–2 minutes afterward, and apply a heating pad to help the oil disperse. Alternating sides (left buttock one day, right the next) prevents scar tissue buildup. Most surrogates say the first week is the hardest, and it gets easier quickly.
PIO injections use a longer needle than most at-home injections — typically 1.5 inches — to reach the muscle. The oil is thick, so the injection goes in slowly. Most protocols require daily injections, at least initially. Having a partner give the injection makes the process considerably easier when you are relaxed.
Are There Alternatives to Progesterone Injections?
Some clinics use vaginal progesterone suppositories — such as Endometrin or Crinone gel — instead of or alongside injections.
Suppositories deliver progesterone directly to the uterus, requiring lower systemic doses. They avoid injection site soreness entirely, but require insertion 2–3 times daily and can cause vaginal discharge. Some protocols combine injections plus suppositories for surrogates who need higher progesterone levels.
Progesterone affects a wide range of systems in the body. Common side effects include:
- Injection site soreness, lumps, and bruising. The most frequent complaint. Rotating sites and warming the oil help significantly.
- Fatigue. Progesterone is naturally sedating. Many surrogates report feeling more tired than usual, especially early on.
- Bloating and cramping. Mild abdominal bloating, especially in the days leading up to the transfer.
- Mood changes. Some surrogates feel more emotional or anxious; others feel calmer. Progesterone affects everyone differently.
- Constipation. A less-discussed but real side effect. Staying hydrated and eating enough fiber helps.
- Breast tenderness. Similar to what many women experience before a period, but can be more pronounced.
All of these side effects are temporary. Once progesterone tapers after the first trimester, they resolve.
The Embryo Transfer Procedure
Quick Answer
The embryo transfer itself takes about 15–20 minutes and does not require anesthesia. Most surrogates describe it as mildly uncomfortable — similar to a pap smear — rather than painful. You will rest briefly at the clinic and then go home.
After 5–7 days of progesterone, the transfer is scheduled. You will arrive at the fertility clinic with a moderately full bladder — this helps with ultrasound visualization during the procedure.
A speculum is inserted, and a thin, flexible catheter is guided through the cervix into the uterus. The embryo is placed through the catheter into the uterine cavity.
Many surrogates go about their normal day afterward; some prefer to rest for 24 hours. Your clinic will give you specific guidance on activity restrictions post-transfer. For a full breakdown of what the procedure feels like, read our post on what embryo transfer is like for surrogates.
The Two-Week Wait: What Happens After the Transfer
The period between the embryo transfer and the pregnancy blood test is commonly called the “two-week wait” — though it is usually closer to 10 days, confirmed by a blood test (called a beta hCG test).
During this time, you continue all medications exactly as prescribed.
The embryo either implants or it does not — your activity level, diet, or how much you rested does not change the outcome. Your role during this window is to keep taking your medications and take care of yourself.
What Happens If the Embryo Transfer Does Not Result in Pregnancy?
Not every transfer results in pregnancy, even with good embryos and a well-prepared lining. If the beta hCG comes back negative, it is emotionally hard for both you and the intended parents.
Give yourself time to process it. Most clinics wait one to two menstrual cycles before attempting another transfer. You can read more about handling a failed IVF transfer as a surrogate — what to expect emotionally and medically.
After a Positive Test: Medications Continue Through Week 12
A positive beta hCG means the embryo implanted. The medications do not stop there. You continue estrogen and progesterone for several more weeks — typically through 10–12 weeks of pregnancy, when the placenta develops enough to produce its own hormones.
The clinic gradually tapers the doses rather than stopping abruptly. Most surrogates feel relief when the injections finally end, and by that point the pregnancy is well established.
The Full Surrogate Hormone Protocol at a Glance
| Phase | Medications | How Long |
|---|---|---|
| Suppression (if used) | Birth control pills or Lupron | 2–4 weeks |
| Estrogen phase | Estradiol (oral, patch, or injection) | 2–3 weeks |
| Lining check | Ultrasound to confirm thickness | 1 appointment |
| Progesterone phase | PIO injections and/or vaginal suppositories | 5–7 days pre-transfer |
| Embryo transfer | The procedure itself | ~15–20 minutes |
| Two-week wait | Estrogen and progesterone continue | ~10 days |
| Early pregnancy support | Estrogen and progesterone tapered off | Through weeks 10–12 |
Every clinic has its own protocol preferences. Your specific timeline and doses come from the fertility clinic working with your intended parents, and your coordinator walks you through everything before it starts.
The full surrogate hormone protocol — from suppression through embryo transfer — typically spans 6–8 weeks. Medications continue through weeks 10–12 of a confirmed pregnancy, after which the placenta takes over hormone production on its own.
How Physician Oversight Makes the Medication Process Safer
At most surrogacy agencies, no doctors work on staff. When a surrogate has a question about her medications or notices a side effect that concerns her, coordinators relay messages between her and outside physicians — with no one at the agency able to evaluate her situation directly.
Physician’s Surrogacy operates differently. Our in-house OB/GYNs stay involved throughout your journey, including the medication phase. If something comes up — a side effect that seems more serious than expected, a lab result that needs review, a question about your specific protocol — a physician on our team can look at your actual case, not just pass along a message.
Our physicians can also communicate directly with the fertility clinic’s RE if there is a clinical question about your protocol. That peer-to-peer coordination is something agencies without in-house physicians simply cannot offer. It is one of the reasons our preterm delivery rate sits 50% below the national average — physician oversight at every stage, including the weeks leading up to the transfer.
To learn more about what makes our physician-led approach different, visit our Physician’s Advantage page.
Ready to Become a Surrogate? Here Is What to Expect
If you are considering becoming a surrogate and the medication process feels daunting, that is a completely normal reaction. Giving yourself daily injections is not something most people have done before. What surrogates consistently say, looking back, is that it is more manageable than it sounds. The protocol is short, the medications are well-studied, and you are supported at every step.
At Physician’s Surrogacy, we walk every surrogate through the full medication process before they commit to anything. You will know exactly what to expect — which medications, which form, what side effects typically look like, and what support is available — before you sign anything.
Check our surrogate requirements to see if you qualify. When you are ready, apply to become a surrogate and our team will be in touch.
Schedule A ConsultationFrequently Asked Questions
Do surrogates have to give themselves injections? +
How long do surrogates take hormones before the embryo transfer? +
What happens to the hormones after a positive pregnancy test? +
Can I still take my regular medications during the surrogate protocol? +
What if I have a bad reaction to the progesterone injections? +
Julianna Nikolic
Chief Strategy Officer Julianna Nikolic leads strategic initiatives, focusing on growth, innovation, and patient-centered solutions in the reproductive sciences sector. With 26+ years of management experience and a strong entrepreneurial background, she brings deep expertise to advancing reproductive healthcare.
