How to calculate your IVF or FET due date

Sometimes, starting a family requires a little extra assistance from a reproductive endocrinologist or a fertility specialist. People who use assisted reproductive technology (ART), which includes fertility treatments involving eggs or embryos, have to learn a lot of details about fertilization and implantation that they never thought they’d need to know. If you conceive via in vitro fertilization (IVF), your due date calculation will change to factor in this conception process.

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IVF due date vs. natural conception due date

Although it varies from woman to woman, a typical pregnancy lasts 40 weeks, or about 280 days. When you get pregnant without the assistance of IVF, there are several ways to figure out your due date based on your menstrual cycle or the date of conception. The most common strategy is to count forward 280 days from the first day of your last period (assuming that you remember that piece of information).This method works well if you have regular menstrual periods, but is less reliable for those with irregular cycles. Or to make it easy on yourself, you can use a natural conception pregnancy due date calculator.

However, when you go through the in vitro fertilization and embryo transfer process, your IVF due date will be two weeks shorter because you don’t account for the last menstrual period or ovulation.

“Since a last period doesn’t say much about when you actually get pregnant following IVF, the due date following IVF is calculated based on the ‘age’ of the embryo, usually day 3 or day 5, and when the embryo is transferred,” explains Jessica Ryniec, MD, an OB-GYN and reproductive endocrinology and infertility specialist at CCRM Boston. “This makes the due date from IVF more accurate to predicting 40 weeks of pregnancy because we know closer to when the person conceived.”

When is my due date?

This IVF due date calculator can help you figure out when your baby is likely to be born:

How to calculate due date with IVF and FET

When you undergo IVF and a fresh embryo transfer (FET), you’ll add 38 weeks, or 266 days, to the date of the egg retrieval to get your due date, explains Luis Murrain, DO, an OB-GYN and cofounder and partner physician with Dreams Fertility in Palm Springs, California. That calculation holds true if you’re using your own eggs or if you’re using donor eggs or a donor embryo.

If you choose to calculate from the date of the embryo transfer, however, you’ll need to do a little more math. You’ll add 266 days but then subtract three days for a Day 3 transfer or subtract five days for a Day 5 transfer. The number of days indicates how many days since the egg was fertilized (mixed with sperm in a petri dish). With a frozen embryo, it’s calculated the same way.

“This is because the embryo is frozen in time,” Dr. Ryniec says. “So even if you transfer the embryo next month, next year, or in 10 years, it is still a Day 3 or a Day 5 embryo, so you can still add 263 or 261 days from transfer day.”

Are IVF due dates more accurate than natural conception?

Knowing your embryo transfer date might take some guesswork out of calculating your due date because you’re eliminating a common variable—that is, misremembering the date of your last menstrual period or common menstrual confounders such as an irregular cycle or spotting (that is not a true menstrual period).

Unless you schedule a caesarian section in advance or plan to induce labor at a particular point, the only person who really has any control over your actual delivery date is the baby. The reality is that babies can arrive on their due dates, but often they don’t. That goes for babies who are conceived without the help of IVF and for babies who are conceived with the help of modern technology.

“The due date is an estimate based on the average gestational period of a 40-week full-term pregnancy,” Dr. Murrain says. “Most babies, regardless of the method of conception, do not deliver exactly on their due date.”

Or as Dr. Ryniec puts it, “Due dates from IVF are the most accurate to 40 weeks that they can get. However, that doesn’t mean they will actually predict when the baby ends up being born.”

That uncertainty can be frustrating, but keep in mind that your provider is keeping track because the due date can help with assessments about your baby’s maturity, including lung development, in the later stages of your pregnancy.

“This is particularly important if the doctor is contemplating an induction of later because in his or her opinion, the intrauterine environment is compromising the well-being of the baby, or if the mother has an illness and the continuation of the pregnancy is posing risks,” explains Joel Batzofin, MD, co-founder and medical director of Dreams Fertility.

Fresh vs. frozen embryo transfers

If you’re going through IVF, here’s what you might need to know about the difference between fresh and frozen embryo transfers. As you can probably surmise, one transfer involves freshly created embryos and the other involves embryos that were created at some time in the past and then frozen and stored.

Typically, a fresh embryo transfer occurs three or five days after egg retrieval for fertilization, according to the Society for Assisted Reproductive Technology (SART). Typically, retrieved eggs are fertilized the day of retrieval, unless they are being harvested for freezing. By contrast, a frozen embryo could be frozen for months, or even years, before being thawed out and then transferred into the uterus. Frozen embryo transfers are very common, according to SART, with some people choosing to use frozen embryos left over from a previous cycle.

One thing you won’t need to worry about is whether or not your estimated due date (EDD) will be affected by whether your embryo was freshly created or spent some time in the freezer. “The due date should be the same whether you are transferring a fresh or a frozen embryo,” Dr. Murrain says.

Will ICSI affect my due date?

One type of procedure that can help a person who needs help conceiving is intracytoplasmic sperm injection (ICSI). During this procedure, a single sperm is injected with a tiny needle called a micropipette directly into the egg to fertilize it. The day the egg is injected with sperm is considered day 0. Meaning, it is considered the day of fertilization, similar to typical IVF. Then the fertilized egg will grow for several days in the lab before being transferred into the woman’s uterus.

ICSI is often used when the male half of a couple does not produce enough sperm to use a method like intrauterine insemination (IUI) or traditional IVF, or he has a blockage that prevents the sperm from getting out. ICSI is also an option if the sperm isn’t moving normally, or the sperm is having trouble penetrating the egg.

According to the American Society for Reproductive Medicine, ICSI is effective in fertilizing eggs 50%-80% of the time, but not all the fertilized eggs will grow into embryos. “It does not change when fertilization occurs or when the due date will be,” Dr. Ryniec says.

RELATED: How a dad’s health impacts his baby’s

What is the best day to transfer an embryo?

You may be wondering what the optimal date of transfer is. After all, you want your best chance at a successful transfer and implantation. According to Dr. Ryniec, it depends.

“The goal of embryo transfer is to give the best chance for pregnancy and live birth while also minimizing risk of multiples,” she says. “Oftentimes, a day 5 transfer is preferable because it allows greater confidence in a single embryo transfer without compromising pregnancy rates. This is because we have more information about which embryo is best.”

But for some people a day 3 embryo transfer could be the better option. “Day 3 embryo transfer may be better for people with fewer embryos growing,” Dr. Ryniec continues. “Ultimately the decision should be individualized and discussed between patient and doctor as well as the embryologist.”

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How many weeks pregnant am I after IVF or FET?

Regardless of how you conceived, you will still count your pregnancy by weeks, rather than months. The number of weeks of gestation translates to one of three trimesters.

First trimester: Week 1 through Week 12

During this trimester, some women experience “morning sickness” symptoms like nausea and vomiting, as well as fatigue. The fetus’s brain, spinal cords, and organs begin to form, and the heart begins to beat.

Second trimester: Week 13 through Week 26

During the second trimester, morning sickness symptoms may begin to taper off, and your energy levels may return. You may also detect some gentle fluttering movements in your uterus, a sign the baby is moving around.

Third trimester: Week 27 onward

As you continue to put on a few more pounds, your baby is growing fast, too—and developing new movements, such as opening and closing eyes, as well as kicking and stretching and grasping.

When you calculate your IVF pregnancy due date, you will learn how far along you are in your pregnancy, and what to expect from there.

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