Hormones Surrogates Take: A Complete Guide to the Embryo Transfer Protocol

When you start researching surrogacy, you’ll quickly run into terms like “hormonal stimulation,” “fertility medications,” and “IVF protocol” — and it’s not always clear which parts of that apply to you as a surrogate.

Here’s the short answer: you don’t go through ovarian stimulation or egg retrieval. Those are processes for the person providing the eggs — the intended mother or an egg donor. Your hormonal protocol is different, and honestly simpler.

The hormones surrogates take are designed to do one thing: prepare your uterus to receive and support the embryo. This guide covers exactly what that involves — which medications, what they do, what side effects to expect, and what the full timeline looks like from start to pregnancy confirmation.

Key Takeaways

• Surrogates do not take FSH or undergo ovarian stimulation — that’s what egg donors and intended mothers go through.
• The two main hormones surrogates take are estrogen (to build the uterine lining) and progesterone (to stabilize it for the embryo).
• Most surrogates describe the process as manageable, with progesterone injections being the part that requires the most adjustment.
• The full medication protocol typically runs from 6–8 weeks before the transfer through the first 10–12 weeks of pregnancy.
• All medications are administered under physician supervision and are safe and well-studied for this purpose.

This article is for informational purposes only and does not constitute medical advice. Consult with a qualified medical professional for guidance specific to your situation.

Why Surrogates Need Hormonal Preparation at All

In a natural pregnancy, your body’s own hormonal cycle prepares the uterine lining every month. Estrogen builds the lining up, progesterone stabilizes it, and if a fertilized egg arrives at the right moment, it has a ready environment to implant.

In a frozen embryo transfer (FET) cycle — which is how most surrogacy transfers work — the fertility clinic needs to control that timing precisely. They can’t rely on your natural cycle to produce the right conditions on the exact day the embryo is ready to transfer.

So instead, the clinic takes your natural cycle out of the equation and creates the right uterine environment artificially, using estrogen and progesterone at specific doses and timing. Your body does what it would naturally do — just on a controlled schedule that syncs with the embryo.

That’s the whole purpose of the surrogate hormonal protocol. It’s not complicated, and it’s not the intense process that ovarian stimulation involves. It’s targeted preparation for one specific goal.

Step 1: Suppression (Not Always Required)

Some fertility clinics start the protocol with a suppression phase to regulate your cycle before building it back up on their schedule. This is more common in certain protocols but not universal — your specific clinic may or may not include this step.

Birth Control Pills

The most common suppression method. You’ll take oral contraceptive pills for 2–4 weeks before estrogen begins. This quiets your natural hormonal fluctuations so the clinic can start estrogen at a predictable baseline.

Side effects during this phase are the same as standard birth control: possible mood changes, light spotting, breast tenderness, or nausea. Most women tolerate this phase without much disruption.

Lupron (Leuprolide Acetate)

Some protocols use Lupron — 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.

Lupron is given as a daily subcutaneous injection, typically in the abdomen. Side effects can include hot flashes, headaches, and mood changes — essentially mild temporary menopause-like symptoms. These resolve once you stop taking it.

Not all clinics use Lupron for FET cycles. It’s more common in protocols where very precise cycle control is needed.

Step 2: Estrogen — Building the Uterine Lining

Once suppression (if used) is complete, estrogen begins. This is the phase where your uterine lining — called the endometrium — develops to the right thickness and texture to receive the embryo.

What Estrogen Does

The endometrium needs to reach a minimum thickness — typically at least 7–8mm — for the transfer to proceed. Estrogen drives that growth. It also affects the lining’s receptivity, making it hospitable for an embryo to implant.

The clinic monitors your lining with transvaginal ultrasound during this phase, usually 1–2 times, to confirm it’s developing properly before moving forward.

How Estrogen Is Taken

Estrogen comes in several forms, and different clinics prefer different delivery methods:

• 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. 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 methods.

Your clinic will specify which form and dose they prefer. The estrogen phase typically lasts 2–3 weeks.

Estrogen Side Effects

Most surrogates find estrogen easy to tolerate. Common side effects are mild:

• Bloating
• Breast tenderness or fullness
• Mild nausea, especially early on
• Headaches
• Mood changes — some women feel more emotional, others notice no difference
• Light spotting (more common with vaginal forms)

These are temporary and typically ease as your body adjusts. If you experience severe nausea or headaches that don’t respond to over-the-counter relief, let your coordinator or care team know.

Step 3: Progesterone — Stabilizing the Lining for Transfer

Once your lining has reached the target thickness, progesterone is added. This is the hormone that most surrogates have the most to say about — it’s effective, it’s necessary, and it comes with some side effects worth knowing about upfront.

What Progesterone Does

In a natural cycle, progesterone rises after ovulation and prepares the lining to support an implanting embryo. It essentially puts the lining in “ready to receive” mode — shifting it from a growth phase to a receptive phase.

In a FET cycle, the clinic adds progesterone 5–7 days before the scheduled transfer, mimicking the natural post-ovulation window. The embryo is transferred into a lining that’s in exactly the right stage of development.

If the transfer results in a pregnancy, progesterone continues for several weeks — typically until 10–12 weeks of pregnancy, when the placenta takes over its own progesterone production.

How Progesterone Is Taken

This is where most surrogates have questions, because progesterone is most commonly given as an intramuscular injection — and that’s an adjustment.

Progesterone Injections (PIO)

Progesterone in oil (PIO) injections are administered intramuscularly, typically in the upper outer quadrant of the buttocks. The oil base — usually sesame, olive, or ethyl oleate — is what makes the injection effective and long-lasting, but it’s also what makes the injections uncomfortable.

Here’s what to expect:

• Needle size. PIO uses a longer needle than most at-home injections — typically 1.5 inches — to reach the muscle.
• Consistency. The oil is thick, which means the injection goes in slowly and the site can feel sore for hours afterward.
• Frequency. Most protocols require daily injections, at least initially.
• Site rotation. Alternating sides (left buttocks one day, right the next) helps prevent buildup of scar tissue.

Tips that actually help:

• 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 after each injection to help the oil disperse.
• Apply a heating pad to the injection site afterward.
• Have your partner give the injection if possible — it’s much easier when you’re relaxed and not trying to reach your own backside.

Most surrogates say the first week is the hardest and it gets easier as you find your rhythm.

Vaginal Progesterone Suppositories

Some clinics use vaginal progesterone suppositories (such as Endometrin or Crinone gel) instead of or alongside injections. They deliver progesterone directly to the uterus, which means lower systemic doses are needed.

Suppositories avoid the injection site soreness entirely. The trade-offs: they require insertion 2–3 times daily, can cause vaginal discharge, and some women find them messier to manage.

Some protocols use both — injections plus suppositories — for surrogates who need higher progesterone levels or where the clinic wants additional support.

Progesterone Side Effects

Progesterone affects a lot of systems in the body, which is why the side effect profile is broader than estrogen:

• Injection site soreness, lumps, and bruising. The most common complaint by far. Rotating sites and warming the oil help significantly.
• Fatigue. Progesterone is naturally sedating. Many surrogates report feeling more tired than usual, especially in the first few weeks.
• Bloating and cramping. Mild abdominal bloating is common, 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.
• Vaginal discharge. More common with suppository forms.

These side effects are temporary. Once progesterone is tapered after the first trimester, they resolve.

The Embryo Transfer Itself

After 5–7 days of progesterone, you’re ready for the transfer. The procedure is straightforward and doesn’t require anesthesia.

You’ll come into the fertility clinic with a moderately full bladder — this helps with ultrasound visualization during the procedure. A speculum is inserted (similar to a pap smear), and a thin, flexible catheter is guided through the cervix into the uterus. The embryo is placed through the catheter into the uterine cavity. The whole procedure takes about 15–20 minutes.

Most surrogates describe it as mildly uncomfortable — similar to a pap smear or a period cramp — rather than painful. You’ll rest at the clinic for a short time afterward and then go home.

Many surrogates go about their normal day; some prefer to take it easy 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, our post on what embryo transfer is like for surrogates covers it in detail.

After the Transfer: The Two-Week Wait

The period between the embryo transfer and the pregnancy blood test is commonly called the “two-week wait” — though it’s usually closer to 10 days with a blood test (called a beta hCG test) to confirm pregnancy.

During this time, you continue all your medications exactly as prescribed. The embryo either implants or it doesn’t — your activity level, what you eat, or whether you stayed in bed doesn’t change the outcome. Your job during this window is to keep taking your medications and take care of yourself.

If the Transfer Doesn’t Work

Not every transfer results in pregnancy, even with good embryos and a well-prepared lining. If the beta hCG comes back negative, it’s emotionally hard — both for you and for the intended parents. Give yourself time to process it.

Most clinics wait one to two menstrual cycles before attempting another transfer. The protocol starts again, and a second transfer can be attempted depending on how many embryos are available. Our team supports surrogates through this process — you can read more about handling a failed IVF transfer as a surrogate and what to expect emotionally and medically.

After a Positive Test: Medications Continue

A positive beta hCG means the embryo implanted. But the medications don’t stop there.

You’ll 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 will gradually taper the doses rather than stopping abruptly.

Most surrogates experience some relief when the injections finally stop. By that point, the pregnancy is well established and your body is doing what it needs to do on its own.

The Full Surrogate Hormone Timeline at a Glance

Every clinic has its own protocol preferences. Your specific timeline and doses will be set by the fertility clinic working with your intended parents, and your coordinator will walk you through it before anything starts.

How Physician Oversight Makes the Medication Process Safer

At most surrogacy agencies, there are no doctors on staff. If you have a question about your medications or a side effect that concerns you, coordinators relay messages between you and outside physicians — with no one at the agency able to evaluate your situation directly.

At Physician’s Surrogacy, our in-house Obstetrician/Gynecologists (OB/GYNs) are involved throughout your journey. That includes 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 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 reproductive endocrinologist if there’s a clinical question about your specific protocol. That kind of peer-to-peer coordination is something agencies without in-house doctors simply can’t offer.

It’s one of the reasons our preterm delivery rate is 50% below the national average — physician oversight at every stage, including the weeks leading up to the transfer.

What to Know Before You Apply

If you’re considering becoming a surrogate and the medication process feels daunting, that’s 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’s more manageable than it sounds. The protocol is short, the medications are well-studied, and you’re supported throughout. The injections become routine faster than you’d expect.

At Physician’s Surrogacy, we walk every surrogate through the full medication process before they commit to anything. You’ll know exactly what to expect — which medications, which form, what the side effects typically look like, and what support is available — before you sign anything.

Check our surrogate requirements to see if you qualify, and apply to become a surrogate when you’re ready.

Frequently Asked Questions

Do surrogates have to give themselves injections?

In most protocols, yes — progesterone in oil (PIO) is given as a daily intramuscular injection, usually in the buttocks. Some clinics offer vaginal progesterone as an alternative or use both. It’s an adjustment, but most surrogates say it becomes routine within the first week.

How long do surrogates take hormones before the embryo transfer?

The full protocol — from suppression through the transfer — typically spans 6–8 weeks. The estrogen phase alone is 2–3 weeks, followed by 5–7 days of progesterone before the transfer.

What happens to the hormones after a positive pregnancy test?

You continue estrogen and progesterone through approximately 10–12 weeks of pregnancy, then taper off as the placenta takes over hormone production. The medications don’t stop immediately after the positive test.

Can I still take my regular medications during the surrogate protocol?

Many medications are compatible with the IVF protocol, but this depends on the specific medication. Your physician team reviews your current medications during screening to assess compatibility before the protocol begins.

What if I have a bad reaction to the progesterone injections?

Contact your coordinator and care team right away. Mild soreness is expected, but significant pain, swelling, redness, or warmth at the injection site beyond normal bruising should be evaluated. Switching to a different oil base or adding vaginal progesterone are options your physician team can discuss with you.