Preparing for in-vitro fertilization (IVF) can be a daunting process, even well before you step inside a doctor’s office. One of the first decisions that needs to be made is whether you’ll be undergoing a fresh embryo transfer or a frozen embryo transfer (FET). This is a choice that shouldn’t be made lightly, and certainly not without the advice of your medical provider. Your physician will help you decide which protocol is the right one for your body — and your wallet. 

If you’ve decided to go the frozen embryo transfer route, however, here’s a quick primer on what that entails:

Just as you would with a fresh embryo transfer, the first step in a FET is egg retrieval. The second step is fertilization of one or more of the harvested eggs with partner or donor sperm. Unlike in a fresh embryo transfer, though, the third step is freezing the embryos, also known as vitrification. In this process, the water in the embryos is replaced with a protectant fluid, and the embryos are flash-frozen with liquid nitrogen. The frozen embryos are then stored in a laboratory until you’re ready to use them for your frozen embryo transfer.

So how different is a FET from a “fresh” embryo transfer? Will using frozen embryos significantly affect your pregnancy outcome — or even your due date? Rescripted spoke with Lisa Lucas, RN, the nursing manager at Reproductive Medicine Group, a five-location fertility clinic in Florida, who walked us through everything we need to know about getting a FET.

fertility specialists looking at paperwork

How do you calculate your due date from an FET?

Since your embryo will already be five to six days old at the time of your frozen embryo transfer, “your estimated due date will be approximately 36 weeks from the transfer date,” says Lucas. The due date will be further confirmed, she says, when you have your pregnancy ultrasound and fetal measurements are taken.

How many weeks pregnant am I after an FET?

If you have a positive pregnancy test following your FET (which usually takes place about 8-10 days after the transfer), “you would be considered four weeks pregnant,” says Lucas.

couple with positive pregnancy test

Does it matter when the embryos were frozen or how long they’ve been frozen?

The short answer is no. The embryos are frozen on either day five or six of development, and “studies show that pregnancy outcomes are not significantly affected by the amount of time the embryos are frozen,” says Lucas. 

What does your IVF timeline look like if you’re using frozen embryos?

“For a standard IVF protocol, you can expect to have your egg retrieval approximately 25-30 days following your period,” explains Lucas. “The egg retrieval is day zero and embryos will be frozen at the blastocyst stage on day five or day six. Following your retrieval, you can expect to start your period about one to two weeks later. You will be instructed to start birth control pills in preparation for your FET cycle.”

Patients can also expect additional testing after their egg retrieval, which starts the FET process. To prepare the uterus to receive the embryo, patients will begin hormone injections. “Your transfer can take place as soon as 16 days after beginning injections, but this timing varies greatly and can be longer as well,” says Lucas. “Your transfer will take place approximately six to eight weeks after retrieval.”

How is a FET different from a fresh embryo transfer?

The main timeline difference between a fresh and frozen embryo transfer is that instead of six to eight weeks after retrieval, a fresh transfer “will take place on day five following your egg retrieval,” says Lucas. “The best quality embryo would be chosen on day five and any additional embryos would be frozen on both day five and day six.”

In addition, explains Lucas, a FET cycle is a completely separate process from egg retrieval. “It requires more time than a fresh transfer and a separate set of injections.” This doesn’t mean, however, that doing an FET cycle should be dismissed out of hand, as there are benefits to this type of IVF protocol. “Speak with your doctor to learn what is the best plan of care for you,” advises Lucas. 

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doctor helping patient calculate fet due date

Choosing IVF with a FET protocol

You’ve heard of the two-week wait, right? But what about the six-to-eight-week wait? If going the FET route is the right decision for you, combatting impatience may be the most challenging part of the entire protocol. “Many patients feel that time is their enemy when they are facing fertility,” observes Lucas. But she also emphasizes that if you are doing a frozen embryo transfer, then “time is a crucial piece of having success.” Yes, you will need to play the waiting game, because the transfer doesn’t take place immediately following the egg retrieval. But that’s due to a critical detail: “It takes time to create the perfect environment in your uterus to allow for implantation.” 

The best way to ensure comfort with your IVF decisions is to voice all your concerns with your fertility team. They will help you make the choice that works best for you.

Sarene Leeds holds an M.S. in Professional Writing from NYU, and is a seasoned journalist, having written and reported on subjects ranging from TV and pop culture to health, wellness, and parenting over the course of her career. Her work has appeared in Rolling Stone, The Wall Street Journal, Vulture, SheKnows, and numerous other outlets. A staunch mental health advocate, Sarene also hosts the podcast “Emotional Abuse Is Real.” Visit her website here, or follow her on Instagram or Twitter.