Your Due Date After Infertility or IVF

1

How to Calculate Your Due Date

Young man and pregnant girlfriend face to face and holding hands in field, waiting to meet their baby on the due date
Calculating your due date is more complicated than it appears. Cultura RM/Chev Wilkinson / Getty Images

Finally, after possibly years of trying to conceive, you get a positive pregnancy test result! Your next question will likely be, “What’s my due date?” You want to know how long you have to wait to see this miracle. You could use an online due date calculator. Most work by asking for your last menstrual period.

However, you can figure out your due date yourself, if you want. 

To do this in your head, just...

1.     Note the first day of your menstrual cycle this month

2.     Add seven days

3.     Now, move the month back three months

4.     Add one year

Then, you'll have your due date.

The average gestation for a singleton pregnancy is (generally) considered to be 280 days (or 40 weeks) from your last menstrual period. This method will give you the typical 40-week pregnancy.

However, due dates are more complicated and less certain than that. Also, due dates after infertility or after IVF can be a little different, too. 

2

Why Your Due Date Isn’t Written in Stone

Woman circling day on wall calendar, close-up
Think of your due date more like a due period. It's just a best guess. Jeffrey Coolidge / Getty Images

When you first receive your due date, you might think that’s going to be the day. You’ll soon learn, however, that due dates are more like due periods. Only 5 out of 100 babies are born on their assigned due date.

We aren’t able to predict the day a baby will be born with 100 percent accuracy, even when you conceived with fertility treatment.

Most due dates are calculated based on the last menstrual period and assume you ovulated exactly 14 days later. But many women ovulate sooner or later. Even with fertility treatment, we don’t really know when you conceived unless you did IVF.

With Clomid or IUI, you might know when you had your trigger shot. You might know when you got a positive ovulation test result, or you might know when your basal body temperature chart indicated ovulation.

But even that isn’t 100 percent accurate. Studies have found that ovulation can occur a few days off from what a positive ovulation test or BBT chart indicates.

Also, implantation of the embryo also varies. The time of implantation can also affect how long you’ll be pregnant.

You may also be surprised to learn that we don’t know for certain how long human gestation is. Primarily, this is because the moment of conception is hidden. It’s not an easy topic to study. With the exception of IVF, we have no idea when it happens.

Some studies say 280 days (or 40 weeks) is the best guess for a due date. Other studies say 282 days (or 40 weeks and 2 days) is better.

Due dates are complicated.

3

Your Due Date After IVF

IVF treatment
Only during IVF treatment do we know the exact moment of conception. Science Photo Library / Getty Images

As mentioned earlier, it’s usually impossible to know exactly when conception took place.

That’s not the case with IVF. IVF—which stands for in vitro fertilization—is literally translated as “fertilization in the lab.” If you conceived with IVF, your doctor knows exactly when you conceived.

However, IVF due dates aren’t calculated based on fertilization day. They are calculated based on the embryo transfer date.

If you had a Day 5 embryo transfer, your due date should be 261 days later.

If you had a Day 3 embryo transfer, your due date should be 263 days later.

Use this nifty IVF calculator to figure out your due date.

Sometimes (in a non-IVF conceived pregnancy), due dates are adjusted or changed. This may occur after an ultrasound if the size of the fetus doesn’t match what would be expected based on the last menstrual period.

However, after IVF, if a future ultrasound indicates a “wrong due date,” your due date will not change. More likely, your doctor will closely monitor the pregnancy for a while. The fetus may not be developing as expected.

4

Why You Might Go Into Labor Earlier Than Expected

7 Pounds 12 Ounces
Layland Masuda / Getty Images

While you might hope that you will get to see your baby sooner than later, you wouldn’t want them to be born too early. Unfortunately, preterm labor is a risk of infertility and IVF-conception.

History of infertility: Women who struggled to conceive are more likely to give birth early. They are at a higher risk of premature labor, which can be threatening to your baby’s health. This is true even for singleton pregnancies. (You don’t have to have twins for your risk of premature labor to go up.)

The theory is that whatever hormonal imbalances caused the infertility also impact the hormones regulating pregnancy and childbirth.

Twins or More: Most people know that the more babies growing in your womb, the more likely you’ll give birth early. Twins tend to be born earlier than singletons. Triplets tend to be born earlier than twins. Quadruplets tend to be born earlier than triplets.

Your doctor may even give you two dates: a regular due date and a slightly earlier date, with the explanation that twins sometimes come sooner. This doesn’t mean your babies will be ready for the world at birth sooner. Just that you shouldn't be surprised if you go into labor earlier.

Slow or abrupt increase in progesterone: The corpus luteum—which is formed from the follicle that released the egg—produces progesterone soon after ovulation.

When pregnancy occurs, pregnancy hormones signal the corpus luteum to continue to produce progesterone and increase those levels. For some women, the levels rise rapidly. Others get a slow and later rise.

Research has found that women with the more sluggish progesterone rise tend to give birth earlier. You might know if your progesterone has the more “sluggish” pattern from close monitoring in an early IVF pregnancy. 

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