What is the Difference Between an Ovulation and Pregnancy Test

Published on February 16th, 2021

Deciding you’re ready to have a baby can be a big moment in your life. You may have done some serious thinking, had some important conversations… or find you’re playing peek-a-boo with every baby at the grocery store, on your morning walks, in work Zoom video calls…

Yup, it might be time!

With that decision comes a rush of excitement, a touch of nervousness, and definitely more questions. If you find yourself puzzling over the family planning aisle of your nearby drug store, you might be wondering about the difference between ovulation tests and pregnancy tests and how to use them. 

Ovulation Test vs Pregnancy Test: The Basics 

The difference between an ovulation test and a pregnancy test lies in what they look for. The two tests measure different things:

  • Ovulation tests detect fertile periods An ovulation test determines when your body is at its most likely to become pregnant. But what does that actually mean? Essentially, an ovulation test tells you when your body has released a fresh egg ready for baby-making.

Once a month, your ovaries — your egg-producing organs — release an egg into your womb. Ovulation tests detect specific hormone changes that indicate an egg has arrived and is ready to become the beginnings of a bundle of joy (more on the science of that later).

  • Pregnancy tests detect pregnancy – Pregnancy tests are used to detect — well, you can probably guess — pregnancy! When a woman becomes pregnant, her body immediately begins to produce hormones to support the development of the baby. These hormones are different than the ones associated with ovulation.

Essentially, a pregnancy test looks for specific pregnancy hormones that indicate your latest egg has become a bun in the oven. 

Ovulation tests look for hormones that indicate your body is at peak readiness to make a baby. Pregnancy tests look for hormones that mean a baby is already on the way. 

Can I use an ovulation test as a pregnancy test? 

Nope—the only thing an ovulation test can tell you is when your body is at its peak fertility and has the best chance of resulting in pregnancy. While it may not tell you if you’re pregnant, an ovulation test kit is a useful tool when you want to start trying for a baby.

Ovulation, Pregnancy, and The Body 

To understand the nuances of ovulation and pregnancy, let’s go back to health class and review the female reproductive system — but with fewer awkward health teacher euphemisms and banana demonstrations.

The Menstrual Cycle 

You may have heard the term “cycles” in reference to a woman’s body. In your day-to-day, that may just mean going through days where life continues as normal and days when you’re dealing with tampons, extra cheese pizza hankerings, and a constant need for the hot pad.

But there’s a whole lot more going on in your body besides the occasional moodiness and craving for ice cream.

A woman’s reproductive cycle, also referred to as the menstrual cycle, is biologically designed to keep a fresh egg available for fertilization as often as possible. Species survival — that is, the innate urge to make more little people to ensure the existence of humankind — is quite literally coded into our DNA. You can almost say that a woman’s body is designed to encourage pregnancy. 

Does that mean your period cramps are DNA’s way of punishing you for not getting pregnant? It sure feels like that sometimes!

The menstrual cycle typically lasts for 28 days and happens in four stages:

  • Menstruation – Day one of your cycle starts on the first day of your period. Your body wants to make a warm and nourishing environment for a new baby. And what does any good host do before a guest comes to stay? Change the sheets in the guest bedroom.

Menstruation breaks down the lining of your uterus and the previous cycle’s egg to make room for a more nourishing environment and a new, healthy egg. The lining turns into menstrual fluid and exits the body through the vagina. This can last between a few days and just over a week. Yup, the least fun part of the cycle.

“But wait,” you might be thinking. “What’s wrong with that other egg? Why can’t it stick around until a sperm finds it?” After an egg is released, it is only viable for 12-24 hours. So out with the old, in with the new!

  • Follicular phase – The next stage of your menstrual cycle starts at the same time as your menstruation but continues on to ovulation. This is the stage that starts making the “guest room” — guest womb? — ready for a new egg.

This process starts with the pituitary gland. Your pituitary gland is a hormone-producing part of your brain. It’s a major player that controls many aspects of your body’s growth, development, and reproductive function. On the first day of your period, the pituitary gland releases hormones to stimulate follicle growth in your ovaries—think of these follicles as microscopic pre-egg incubators.

During this phase, you’ll typically grow 5 to 20 follicles, each holding an immature egg. The growth of these follicles triggers the lining of the uterus to thicken and prepare for the new guest. At around day 10 of your cycle (so ten days after your period starts), one follicle will develop fully into an egg.

  • Ovulation – To kickstart ovulation, the pituitary gland begins increasing production of a hormone called the luteinizing hormone, or LH, which is the hormone ovulation tests look for! This happens about 2 weeks after the first day of your period.

The luteinizing hormone signals the ovaries to release a matured egg. From there, the egg breaks out of its follicle, passes through the fallopian tube, and settles into the lining of the uterus.

Now the clock starts. The egg has 12-24 hours max to meet a sperm and create an embryo — the cellular beginnings of a baby. This is the fertility window ovulation tests help you pinpoint. The good news is that sperm can live in your body for up to five days after entering the vagina. By timing intercourse around your ovulation window, you can increase the likelihood that sperm will already be there to meet the egg when it drops. 

Luteal phase – Remember the follicle the egg busts out of to make it to the uterus? During the last two weeks of your cycle, the luteal phase, that follicle hangs out on the surface of your ovary. It turns into a structure called the “corpus luteum.” Literally meaning saffron-yellow body in Latin, the corpus luteum repairs the walls the egg broke through to create a yellow, circular gland-like structure. The corpus luteum only forms after ovulation, and its purpose is to release a mixture of hormones, mostly progesterone, after an egg has dropped. These hormones encourage cellular growth to help keep the lining of the uterus the exact right thickness — around 7-8 millimeters.

Why is lining thickness so important? If your egg turns into an embryo, it will implant into the uterine lining. From there, the uterine lining will become your microscopic baby’s source of nourishment. A thick lining helps an embryo develop and will eventually become the placenta, the protective sac that will hold your child as she grows in your womb. The thicker the lining is, the higher chance the egg will implant and result in a successful pregnancy.

If a fertilized egg implants into the uterine lining, your body will begin to produce hormones that the corpus luteum needs to sustain itself, such as human chorionic gonadotropin (HCG). When you take a pregnancy test, HCG is the hormone the test looks for to confirm a pregnancy. (If you’re now wondering “How soon will a pregnancy test read positive?”, you can find out more on our blog!)

If pregnancy doesn’t occur (a fertilized egg doesn’t implant in the uterine lining and no HCG is generated), at around day 22 of your cycle the corpus luteum retires and is broken down by the body. Without the corpus luteum, there is no trigger for your body to produce the progesterone levels needed to maintain the uterus lining. The drop in progesterone causes the lining of the uterus to be discarded. 

Break out the cookie dough and the hot pad—we’re back at menstruation. From there, the cycle starts again.

How do ovulation tests work? 

During ovulation, your body’s LH levels will surge, meaning an egg is ready to meet a nice sperm and start the latest addition to your family. Ovulation tests look for this LH surge in your urine sample.

Ovulation tests can look similar to basic pregnancy tests. They’re strips you either urinate or insert into a cup of your urine.

The ovulation test strip typically has two lines:

  • The control line – This tells you the test is working properly. You also use it to compare the results of your test line.
  • The test line – This line will turn either darker or lighter than the control line to indicate your LH levels. If the line turns lighter than the control line, there’s a low LH level  in your body. If the line darkens, that means there’s a higher LH level in your body and you are officially in your fertility window! 

An ovulation test kit tends to come with multiple test strips to help you seize your peak fertility opportunity when it strikes.

When should I take an ovulation test? 

While there are typical symptoms that may alert you when to take a pregnancy test, this is not the case for ovulation testing. However, because an egg only lives for 12-24 hours after ovulation, it can help to have a solid understanding of your fertility window.

Ovulation occurs at the midpoint of your menstrual cycle, so about 2 weeks after the first day of your period. Start ovulation testing 10 or 11 days after your period starts to make sure you give ample opportunity for your egg to be fertilized.

But not every woman’s body runs like clockwork.

If you have a shorter cycle length (meaning your period only lasts a few days or the time between your periods is shorter), ovulation can start within 4 days of your cycle’s midpoint. In that case, start using the ovulation test 4-6 days prior to the halfway point of your cycle.

If your period lasts a week or more, start ovulation testing on day 10 and keep testing. Even though you’re still experiencing period symptoms, your follicular phase might be well on its way to ovulation. Having extra test strips around can help you pinpoint your fertile period.

As for testing day timing, keep your pee in mind. Excess fluid in your urine can dilute your hormone levels. Here are a few tips to help you get the most accurate results from your ovulation test:

  • Take the test as soon as you wake up in the morning.
  • If taking the test later in the day, try limiting your liquid intake for about 2 hours before testing.
  • For post-morning tests, it can also help to hold off going to the bathroom 1-2 hours before you take the test.

When the Pregnancy Test Reads “Positive,” Trust SneakPeek for Answers 

If you’re just getting started on expanding your family, your questions may look like “When am I most fertile?” “Is it egg drop time yet?” or “How many times do I have to pee on things before I have a baby?”

But once you make the jump from ovulation test strips to a positive pregnancy test, even more questions will come your way about your growing baby-to-be, including, “Am I having a little boy or a little girl?”

SneakPeek can help you find out.

The SneakPeek Early Gender DNA Test can detect your child’s gender as early as 8 weeks into pregnancy with 99.9% accuracy. This simple at-home test comes with detailed instructions and an easy-to-use kit so you can find answers fast. 

Bonus? You don’t have to pee on anything. 

Get your answers sooner with SneakPeek!


MedLinePlus. Ovulation home test. https://medlineplus.gov/ency/article/007062.htm#:~:text=An%20ovulation%20home%20test%20is,ovary%20to%20release%20the%20egg.

MedlinePlus. Pregnancy Test.  https://medlineplus.gov/lab-tests/pregnancy-test

Office on Women’s Health. Menstrual Cycle. 


The Royal Women’s Hospital. Ovulation and conception. https://www.thewomens.org.au/health-information/fertility-information/getting-pregnant/ovulation-and-conception

Parenting. Endometrial Thickness – What’s the Normal Range for Pregnancy? https://parenting.firstcry.com/articles/endometrial-thickness-whats-normal-range-for-pregnancy/

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SneakPeek aims to provide the most accurate and up-to-date information to help our readers make informed decisions regarding their health before, during, and after pregnancy. This article was written based upon trusted scientific research studies and/or articles. Credible information sources for this article are cited and hyperlinked.

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