What Medications You'll Take Before Embryo Transfer

The needles are the part almost everyone asks about first. The medication protocol that prepares your body for embryo transfer is real work — but it's also finite, well-rehearsed, and far more manageable than the word "injections" suggests. Here's what you'll actually take, why, and what those weeks feel like.

Published June 26, 2026 · Updated October 7, 2026

Before an embryo transfer you'll mainly take estrogen, usually as pills or patches for a few weeks to build your uterine lining, and then progesterone, most often a once-daily progesterone-in-oil injection, starting a few days before transfer. Depending on your clinic, the protocol may also include Lupron, birth control pills, a baby aspirin, a prenatal vitamin and sometimes a short course of antibiotics or a steroid, and the intended parents pay for every medication.

In gestational surrogacy, the embryo is already made — created from the intended parents' or donors' egg and sperm — and frozen, waiting. Your body's job isn't to produce an egg; it's to build a warm, ready uterine lining and then hold it steady so the embryo can implant and grow. That's what the medications do. They're not fertility drugs to make you ovulate; they're hormones that recreate, on a controlled schedule, exactly what a body does naturally in early pregnancy. Understanding that makes the whole protocol feel less foreign.

The two hormones at the center of it

Almost every frozen embryo transfer cycle is built on two hormones you already make on your own: estrogen and progesterone.

Estrogen — building the lining

Estrogen comes first, usually a few weeks before transfer, and its job is to thicken the uterine lining so it's ready to receive an embryo. It's typically the easy part of the protocol because it usually isn't an injection. Depending on your clinic, estrogen comes as:

• Oral pills (estradiol), often taken a few times a day.
• Patches worn on the skin and typically changed every couple of days.
• Occasionally injections, though many clinics avoid these for surrogates.

Along the way, you'll go in for monitoring — bloodwork to check hormone levels and ultrasounds to measure the lining. When it's thick enough and the timing lines up, the clinic schedules the transfer and adds the second hormone.

Progesterone — the one people mean when they say "the shots"

Progesterone is the hormone that tells your body to sustain a pregnancy, and it typically starts a few days before transfer. This is usually the part of the protocol surrogates have heard about, because the most common form is progesterone in oil (PIO) - usually a once-daily intramuscular injection, typically into the upper outer area of the buttock. It's a thicker oil than other shots, which is why it has a reputation, but the technique is very learnable and a partner or friend can give it. Some clinics use or add vaginal progesterone (suppositories or gel) instead of, or alongside, the shot. You continue progesterone after a positive test, often into the first trimester (commonly around 8 to 12 weeks), until the placenta takes over hormone production on its own.

The supporting cast

Around those two, your protocol may include a few smaller players, depending on the clinic:

• Lupron or a similar medication early on, to quiet your own cycle so the clinic — not your ovaries — controls the timing.
• Birth control pills beforehand, which sounds backwards but is just a scheduling tool to sync your cycle to the clinic's calendar.
• A baby aspirin daily to support blood flow to the lining, and a prenatal vitamin, which you'll likely start well before transfer.
• Sometimes a short course of antibiotics or a steroid around transfer.

What it actually feels like

The honest answer: the side effects are usually mild and very pregnancy-like, because they're driven by the same hormones. Surrogates commonly report bloating, breast tenderness, mood shifts, mild headaches, and some fatigue. The PIO injection site can get sore or develop a small knot over weeks of daily shots — warming the oil, rotating sides, and a heating pad or massage afterward all help, and your nurse will coach you through it. None of it is meant to be painful in a serious way, and if anything feels off, your clinic wants the call. Most surrogates settle into the routine within the first week and describe it as tedious more than hard.

The rhythm of a cycle

Pulled together, a typical medicated frozen transfer cycle runs something like this: a few weeks of estrogen with monitoring visits to build the lining, then progesterone added a handful of days before transfer, then the transfer itself — a quick, no-anesthesia procedure — followed by the two-week wait before the first pregnancy test. If that test is positive, you typically stay on estrogen and progesterone through the early weeks and taper off on your clinic's schedule as the placenta takes over. It's a lot of small daily steps, but it's a clear, finite schedule with a clinical team watching every number along the way.