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Are you looking to add a little one to the family? If so, you may be wondering when you have the highest chance of getting pregnant.
There are a couple of terms key to conceiving that you may have already come across in your research: high fertility and peak fertility.
Though they sound similar, they are not the same.
Confused? You’re not alone. Fertility can feel quite complex with all the terms and information.
That’s why we’ve put together this article to help you understand fertility and the ideal time to get busy in the bedroom for the greatest chances of getting pregnant.
A quick refresh on the menstrual cycle
The day you start bleeding marks the first day of your menstrual cycle and a low point for your hormones.
These low hormone levels trigger your pituitary gland to release follicle-stimulating hormone (FSH). As a result, follicles start growing on the surface of the ovary.
One follicle reigns as queen, dubbed the dominant follicle, and once it’s fully mature, it secretes estrogen – about 3-4 days before ovulation.
Once this happens, congratulations – you’ve made it to your fertile window! This rise in estrogen suppresses your FSH levels. Once your estrogen stays flying high for 48 hours, your hypothalamus reacts by surging your LH levels.
And anywhere from 8-20 hours after this LH surge, ovulation happens. Your dominant follicle remnant becomes your corpus luteum, which starts releasing progesterone – the hormonal star of this phase of your cycle. Progesterone makes your uterus a happy and healthy home for your growing fetus.
If there was sperm already waiting when your egg was released, ding ding ding – fertilization is in process! The fertilized egg journeys through the fallopian tube until it implants in the uterus.
If there was no sperm to fertilize the egg, your inner uterine lining sheds, a.k.a. your period. And the cycle starts all over again.
What is high fertility and peak fertility?
These two terms are key to letting you know when your fertility is high – i.e. when your chances of getting pregnant are the greatest.
Both high and peak fertility happen in your fertile window.
In fact, your fertile window = high fertility days + peak fertility days
Clinical guidelines say that your fertile window lasts about 6 days.
But, it turns out these guidelines don’t speak to the masses. A study found that the estimated fertile window was only seen in about 30% of women.
What does high fertility mean?
TLDR: high fertility = when your estrogen levels start rising.
Your dominant follicle matures and starts to produce estrogen, thus causing a rise in estrogen levels. This marks high fertility and the beginning of your fertile window.
How many days are there in your fertile window? You can count on about 4-5 days before ovulation, the day of ovulation, and one DPO.
Some studies say 5 days before ovulation since the sperm can live for up to 5 days in the female body.
This means you can still conceive before you’ve ovulated if there is sperm in your reproductive tract. So don’t wait for your day of ovulation to get busy in the bedroom!
Once your estrogen levels reach a certain high, they trigger a rise in LH, which takes us to peak fertility.
What does peak fertility mean?
TLDR: peak fertility = when your LH levels rise.
Peak fertility coincides with the day of your LH surge, a.k.a. one day before ovulation. This is the day when your chances of pregnancy are the highest.
Your LH levels start to rise 24-36 hours before ovulation until they reach your LH surge at about 8-20 hours before ovulation.
And once ovulation happens, the clock starts ticking. Your egg is only viable for up to 24 hours after ovulation.
So peak fertility is the day before ovulation and the best time to have sex for max chances of conception.
What is the difference between high fertility and peak fertility?
High fertility starts once estrogen levels rise, which means it happens a few days before ovulation (typically 4-5 days).
Though your chances of conceiving during high fertility are, well, high, they are lower than your peak fertility days.
Peak fertility starts once LH levels rise, which means it happens 24-36 hours before ovulation. This means that peak fertility typically only lasts from 1-1.5 days (more on this below).
Your chances of getting pregnant are the highest during this 1-1.5 days of peak fertility.
How long does peak fertility last?
There’s no black-and-white answer to this because peak fertility can vary.
As we discussed earlier, peak fertility is the day before ovulation and aligns with your LH surge. Ideally, it lasts for one day.
This is where things enter the gray area. Not all women have a single, dramatic peak to mark their LH surge.
Many women have different types of LH surge patterns, which means peak fertility may last longer than one day.
Let’s take a quick look at the different LH surge patterns.
Single
This is the typical pattern that you see with one obvious LH surge. 48% of women have this pattern.
Biphasic
This looks like one LH spike, followed by a second one. 33% of women see this pattern.
Plateau
In this, LH levels rise and stay high for several days before dropping. 11% of women follow this pattern.
Multiple
This pattern has two or more LH surges. 8% of women see this.
Read more: LH Levels & Surges: What Does a ‘Normal’ LH Level Look Like?
So, depending on your LH surge pattern, you may get more or less peak fertility days.
However, even if you have an LH surge pattern that looks different than the textbook single peak, you still only have one “true” LH surge that triggers ovulation.
Since your egg lives for 24 hours after release, that means it still has those 24 hours to get fertilized.
And this is why you can still get pregnant a day after ovulation, making this a part of your fertile window.
What are the chances of conception during high and peak fertility?
Studies show that your highest chances of conception are during peak fertility, a.k.a. one day before ovulation.
While sperm can live for up to 5 days in a woman’s body, the egg only lives for 12-24 hours – hence, the one day (24 hours) before ovulation is the best shot at pregnancy (since the sperm is already present as the egg gets released).
5 days before ovulation (high fertility): 9% chance
4 days before ovulation (high fertility): 18% chance
3 days before ovulation (high fertility): 27% chance
2 days before ovulation (high fertility): 33% chance
1 day before ovulation (peak fertility): 42% chance
Day of ovulation (high fertility): 20% chance
Day after ovulation (since the egg can survive for up to 24 hours): 8% chance
How do you know your high and peak fertility days?
There are a few ways you can track your high and peak fertility days so you know when to get between the sheets with your partner.
Ovulation calculators and period tracker apps
These online tools/calculators aim to calculate your fertile window using your period date and your average cycle length. But don’t rely upon them – they are only about 21% accurate because they don’t actually take your hormones into account.
Read more: How Accurate Are Ovulation Calculators?
Cervical mucus
Stating the obvious here, but the female body does some incredible things. And, one of those is changing your cervical mucus when you become more fertile.
As your estrogen levels rise (marking high fertility), your cervical mucus consistency becomes clear, stretchy, and watery. And when you reach peak fertility, it looks and feels like egg whites.
This may sound hard to rely upon, and it is – cervical mucus observation can be subjective and hard to interpret for some.
Read more: Cervical mucus 101: What can your cervical mucus tell you about your body?
Ovulation predictor kits (OPKs)
These at-home kits measure LH levels in your urine to give you an idea of your fertile window.
This is great if you have a single LH surge pattern. But, as you can see from earlier, that’s not the case for everyone.
If you have different LH surge patterns, if your hormones are always flying high because of PCOS, or if your hormones don’t fall within the OPK threshold range, then you’re probably going to get false results.
Read more: How Accurate Are Ovulation Tests?
Using the above methods can help you learn your high and peak fertility days as well as predict when you’re going to ovulate. But they can’t actually confirm ovulation, which is what you need to get pregnant.
Enter: progesterone and its urine metabolite PdG. This hormone is needed to confirm ovulation, and Inito is the only fertility monitor that can do that for you.
Inito is the sole monitor that measures all of your fertility hormones – FSH, alpha, and beta LH, estrogen, and PdG (urine metabolite of progesterone).
It does this using just one single test strip to tell you the key info for conceiving:
- High fertility days
- Peak fertility days
- Ovulation confirmation
Is high fertility or peak fertility better?
Though peak fertility marks your highest chances of conception, it only lasts one day. It isn’t very convenient for you to try and schedule sex on that one day (and it kind of takes the fun out of it, right?).
So, even though your high fertility days don’t give you as high of chances of conceiving as your one peak fertility day, the odds are still in your favor! And they allow for more flexibility rather than putting all that pressure on your one peak fertility day.
Because stress can be a major buzzkill for fertility.
Can you have high fertility without peak fertility?
Yes.
High fertility = rising estrogen levels.
Typically, an increase in estrogen coincides with an increase in LH levels. But this isn’t always the case.
And if your LH levels don’t rise, you can’t ovulate.
What does this mean for your fertile window? That it didn’t actually happen. Either you need to keep testing, or you may not have ovulated this month.
Is the latter cause for concern? If this only happens 1-2 cycles a year, no. But if this happens more regularly, then it’s time to talk to a doctor to see if something is amiss.
Read more: Anovulation: Everything you need to know about the #1 cause of infertility
Can you have peak fertility without high fertility?
Yes.
This can happen if your estrogen (E3G) levels are low or if there wasn’t enough info on your unique baseline hormone levels.
What happens after high fertility and peak fertility?
If you’ve had both HF and PF, this means your estrogen and LH levels are where they need to be for ovulation to happen.
This means *drumroll please* – it’s time to have unprotected sex.
But remember, to confirm ovulation, your progesterone and its metabolite PdG levels also need to rise. The best way to monitor this rise in PdG and confirm ovulation is with Inito. That’s because Inito measures your PdG levels, along with FSH, LH, and estrogen on a single test strip so you can track your fertile window and confirm ovulation.
Frequently Asked Questions
Can you go from low fertility to peak fertility in one day?
If your estrogen (E3G) levels take a long time to rise, you can get a “peak fertility” result directly without “high fertility”.
I had two/multiple peaks in my cycle. What does it mean?
It’s possible to get a false LH surge before the true one. A false one looks like an LH rise that doesn’t mark the start of ovulation. (Since your LH peaks 8-20 hours before ovulation, the true LH surge triggers ovulation.)
The only way to know if you’ve had a true LH surge is to test for PdG (urine metabolite of progesterone).
If this happens to you, don’t worry! About 41% of cycles have more than one LH surge.
Read more: LH Levels & Surges: What Does a ‘Normal’ LH Level Look Like?
Is peak fertility and ovulation the same thing?
No.
Peak fertility is connected to your LH surge. And ovulation happens 24-36 hours after LH levels start rising or 8-20 hours after your LH surge.
What do I do when I hit peak fertility?
Peak fertility marks your highest chances of conception, so you want to have unprotected sex on this day.
Can you get pregnant on high fertility and not peak?
Yes.
Because sperm can live in the female body for up to 5 days, your chances of getting pregnant on high fertility days are very high.
If you’re TTC, you want to have unprotected sex every day or every other day in your fertile window, a.k.a. when fertility is high.
Read more: Is Having Sex Everyday Bad When Trying to Conceive?
Is peak fertility too late to conceive?
No. It’s the opposite!
Peak fertility day marks the highest chance of conceiving.
Why am I not hitting peak fertility?
This can happen if your estrogen levels rise without an LH rise to accompany it.
It may not have been your actual fertile window, or maybe you didn’t ovulate this cycle. Keep testing, and if you have more than 1-2 anovulatory cycles per year, consult a doctor.
Can peak fertility be wrong?
This depends on what method you’re using to track your fertility.
Ovulation calculators only have 21% accuracy. And OPKs are confined to threshold values, thus creating lots of room for error. This can give you inaccurate results for peak fertility.
Using a fertility monitor like Inito that tracks your PdG levels to confirm ovulation and LH + estrogen to predict your fertile window, gives you 96% accuracy in tracking both your high fertile and peak fertile days.
In review
- High fertility happens a few days before ovulation and is marked by a rise in estrogen.
- High fertility usually lasts 4-5 days before ovulation due to sperm’s ability to survive up to 5 days in the female reproductive system.
- Peak fertility is the day before ovulation when LH levels surge.
- Peak fertility usually lasts 1-1.5 days but can vary.
- The highest chances of conception are during peak fertility.
- Some methods to identify high and peak fertility days include ovulation calculators and period tracking apps, cervical mucus observation, and OPKs.
- These methods are not highly accurate because they can’t actually confirm ovulation – they can only predict it.
- Progesterone is the only hormone that can confirm ovulation.
- The Inito Fertility Monitor measures all four of your fertility hormones to track and confirm ovulation.
- You can have high fertility without peak fertility if your estrogen levels have risen but your LH levels are still low.
- You can have peak fertility without high fertility if your estrogen level readings were low or if there wasn’t info on your reference baseline values.
- Though peak fertility marks your highest chances of getting pregnant, trying to schedule sex for that one day may be difficult. So try to have sex in your fertility window every day or every other day for your best chances of conception.
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