A fresh embryo transfer is when an embryo created through IVF is placed into your uterus during the same cycle as your egg retrieval, without being frozen first. The transfer typically happens three to five days after the eggs are collected. It’s one of two main approaches in IVF. The alternative, a frozen embryo transfer, involves freezing all embryos and transferring one in a separate, later cycle.
Day 3 vs. Day 5 Transfers
After your eggs are fertilized in the lab, the resulting embryos are cultured in an incubator. Your clinic will transfer the embryo at one of two stages: day 3 (called cleavage stage) or day 5 (called blastocyst stage). On day 3, a healthy embryo has around eight cells. By day 5, it has developed into a blastocyst, a more complex structure with roughly 100 or more cells organized into distinct groups that will eventually form the baby and the placenta.
Day 5 transfers have become the more common choice. The reasoning is straightforward: in a natural pregnancy, the embryo reaches the uterus at the blastocyst stage, so transferring at day 5 better mimics normal biology. Culturing to day 5 also acts as a natural selection process. Embryos that can’t develop further stop growing in the lab, which helps embryologists identify the strongest candidates without needing to guess at day 3. By this point, the embryo has also switched from relying on the egg’s original genetic instructions to running on its own genome, another sign of viability.
How Embryos Are Selected
Before transfer, embryologists evaluate embryo quality under a microscope. For day 3 embryos, they look at the number of cells (eight is ideal), how much fragmentation is present (less than 10% is considered good), whether the cells are roughly equal in size, and whether any cells contain more than one nucleus, which is a red flag. For day 5 blastocysts, grading focuses on how expanded the embryo is, the quality of the inner cell mass (the cluster that becomes the fetus), and the quality of the outer cell layer (which becomes the placenta).
These grades help your team choose the best embryo to transfer. A high-grade embryo has a better statistical chance of implanting, though grading isn’t a guarantee. Lower-grade embryos still produce healthy pregnancies.
What Happens During the Transfer
The transfer itself is a short procedure, often taking just a few minutes. You’ll lie on an exam table, and your doctor will use abdominal ultrasound to guide a thin, soft catheter through your cervix and into your uterus. The embryo is loaded into the catheter by the embryologist and gently deposited into the upper or middle portion of the uterine cavity, at least 1 centimeter away from the top wall of the uterus. Touching the top wall can cause cramping and may reduce success rates.
Ultrasound guidance is standard practice because it significantly improves both pregnancy and live birth rates compared to transferring without visual guidance. Soft catheters are preferred over rigid ones for the same reason. Your doctor will also clear cervical mucus before inserting the catheter, since mucus can interfere with placement. After the transfer, you can get up and walk around immediately. Bed rest afterward hasn’t been shown to help.
Hormonal Support After Transfer
During a stimulated IVF cycle, the medications used to grow multiple eggs disrupt your body’s normal progesterone production. Progesterone is essential for preparing and maintaining the uterine lining, so you’ll need supplemental progesterone after your transfer to support a potential pregnancy. This is called luteal phase support.
Progesterone can be given vaginally, as an injection into the muscle, or orally. Research comparing these routes has found no significant difference in pregnancy outcomes between them, so the choice often comes down to your comfort and your clinic’s preference. Vaginal progesterone (capsules, suppositories, or gel) is the most common option because it’s easier to self-administer than daily injections. Some clinics also add a single dose of a hormone that mimics your body’s natural ovulation trigger, which has been shown to improve ongoing pregnancy rates without increasing the risk of ovarian hyperstimulation.
How Stimulation Affects Your Uterine Lining
One important consideration with fresh transfers is what the stimulation drugs do to your uterine lining. The fertility medications that help your ovaries produce multiple eggs also drive estrogen levels much higher than in a natural cycle. These elevated hormone levels can alter the lining’s receptivity, making it slightly less synchronized with the embryo’s development than it would be in a natural cycle. Research comparing endometrial tissue from stimulated cycles to natural cycles in the same patients confirmed that both major stimulation protocols shift the lining’s gene expression, though some protocols cause less disruption than others.
This is one of the main arguments for the “freeze all” strategy, where all embryos are frozen and transferred in a later cycle when the uterine lining hasn’t been affected by stimulation drugs. That said, millions of successful pregnancies have resulted from fresh transfers, and for many patients the effect on receptivity is not enough to prevent implantation.
Who Is a Good Candidate
Not everyone undergoing IVF will have a fresh transfer. Your clinic may recommend freezing all embryos instead if you’re at high risk for ovarian hyperstimulation syndrome (OHSS), a condition where the ovaries swell and fluid leaks into the abdomen. OHSS risk is higher in fresh transfer cycles because pregnancy hormones from a newly implanting embryo can worsen the condition. Patients who do develop OHSS after a fresh transfer can experience both an early form (triggered by the medications) and a late form (triggered by the pregnancy itself).
Other reasons your clinic might choose a freeze-all approach include elevated progesterone levels on the day of your trigger shot, a uterine lining that isn’t developing as expected, or the need for genetic testing of embryos (which takes several days and requires freezing). Patients with ovulatory disorders or uterine abnormalities are also typically directed toward frozen transfers. In studies examining fresh transfer candidates, the average endometrial thickness on trigger day was about 7.3 millimeters, and patients generally had at least four embryos available.
Success Rates and Cost
Comparing fresh and frozen transfer success rates is complicated because the patients in each group often have different characteristics. In younger patients with a good ovarian response, large studies have generally found similar live birth rates between the two approaches. For women 40 and older with a poor ovarian response, one study found live birth rates of 5.9% for fresh transfers and 6.6% for frozen, a difference that was not statistically meaningful.
The trend in many clinics has shifted toward more frozen transfers, but this doesn’t mean fresh transfers produce worse outcomes across the board. For patients without OHSS risk and with a well-developed lining, a fresh transfer avoids the additional time, cost, and medication of a separate frozen transfer cycle.
On cost, a fresh transfer cycle is typically less expensive because it avoids the fees for freezing, storing, and thawing embryos, plus the medications and monitoring for a separate transfer cycle. A large UK trial found the treatment cost for a fresh transfer averaged about £1,216, compared to £1,538 for a freeze-all cycle, a difference of roughly £322 (around $400 USD). Patient costs for travel and time off were also lower with fresh transfers. However, when total costs through delivery were calculated (including complications like OHSS), the overall expense was similar between the two approaches.
The Implantation Timeline
After a day 5 blastocyst transfer, implantation typically begins within one to two days and can occur over a window spanning roughly three to seven days. For a day 3 transfer, the embryo needs additional time to develop to the blastocyst stage inside your uterus before it can implant, so the window runs from about two to five days after transfer. In either case, you’ll usually take a pregnancy test about 9 to 14 days after your transfer, depending on your clinic’s protocol. The wait can feel long, but testing too early risks inaccurate results from residual trigger shot hormones or an embryo that simply hasn’t produced enough pregnancy hormone yet.