Implantation cramps: Everything you need to know about implantation pain

    Updated 01 November 2022 |
    Published 23 December 2019
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    Medically reviewed by Dr. Barbara Levy, Clinical professor of obstetrics and gynecology, George Washington University School of Medicine and Health Sciences, UCSD Health, California, US
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    Implantation cramps can be a very early sign of pregnancy — but what do we know about them? Read on to find out.

    You may be aware of some of the early signs of pregnancy, such as nausea, breast tenderness, and tiredness. But in the even earlier stages of conception, some people say they can feel implantation cramps as the newly formed embryo attaches to the uterus. So what’s the deal? Could implantation cramps be a very early sign of pregnancy? 

    Even now, there’s very little scientific evidence that documents cramps during implantation, which is why you likely haven’t heard much about them. But that doesn’t mean what you’re feeling isn’t implantation cramping since lots of people have reported similar feelings at the beginning of pregnancy (more on that below). 

    Implantation cramps can often be mistaken for menstrual cramps. That’s because they may feel similar, and it’s a sensation many people who menstruate are familiar with. Think you might be experiencing them? Read on to learn how to recognize the difference, why implantation cramps could happen, and whether you need to see a doctor about them.  

    What do implantation cramps feel like? Signs and symptoms

    It’s a particularly difficult thing to determine whether or not the cramps you’re feeling could be a sign of pregnancy. That’s because implantation — which is when a fertilized egg attaches to your uterine lining — happens really early on, anywhere between 6 and 10 days after the sperm fertilizes the egg. And frustratingly, according to scientific research, there are minimal signs of implantation.

    Along with implantation cramps, lots of people report experiencing implantation bleeding in the early stages of pregnancy. We spoke with OB-GYN (obstetrician and gynecologist) Dr. Jenna Flanagan, who explained: “Some people report spotting or pink discharge at the time of implantation.” She adds that although it can be difficult to prove that this is directly related to implantation, experts do understand why implantation could, theoretically, sometimes cause bleeding. 

    “Given the lining of the uterus is built up with progesterone and estrogen, it is possible that implantation could cause some disruption of the lining and result in some bleeding,” explains Dr. Flanagan. “This is different from menstrual bleeding,” she clarifies, “as that often begins as brown or rust-colored discharge and becomes heavier. In contrast, any spotting around early pregnancy is light, lasts 1 to 2 days, and tends to get lighter.”

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    As we’ve heard, it’s important to note that there is still very little scientific evidence to confirm whether cramps are an official sign of implantation. However, there is plenty of anecdotal evidence from those who have experienced it, including entries from our own Flo community who have shared their experiences.  

    So, what do implantation cramps feel like? As you can see, they can be different for everyone:

    • “My early sign of pregnancy was mild cramps before my period would have happened. I have a regular period, so I knew right away that it was something special. I tested positive, and I’m now carrying twin girls!”
    • “I thought I had PMS cramps, but it was early pregnancy. I was shocked!”
    • “I’m pregnant with my second child. I had cramps two days before my period was due, but it never came.”
    • “My early pregnancy sign included severe backache. I thought it was because my period might be arriving, but it didn’t.”

    As the quotes above show, some people feel what they believe to be signs of implantation. But for many other people, this stage in the conception process can go totally unnoticed. Unfortunately, in this instance, the only thing to do is to wait until the time you’d expect your period to come. Alongside a missed period, there are a number of other signs of early pregnancy that may emerge around this time to suggest you could be expecting. They can include:

    • Swollen, heavier, or tender breasts
    • Morning sickness or nausea
    • Headaches
    • Constipation
    • Mood swings and feeling teary
    • Feelings of extreme tiredness 
    • Feeling dizzy or faint
    • Sudden food cravings or aversions

    Where do you feel implantation cramps?

    Just as with pregnancy, implantation pain differs from person to person. Some may feel just a slight twinge in their lower abdomen, while others may have cramping in their back for several days. And, of course, some may feel nothing at all. Differences in physiology result in a range of experiences, so it really depends on your body.

    How long do implantation cramps last?

    Again, it’s hard to pin down how long implantation cramps last with so little scientific evidence. But, as Dr. Flanagan explains: “Typically, they are very mild, and the person may experience them for a day or two.

    “However, some people experience cramping in early pregnancy for many days, and again, this is likely related to fluctuating hormones and not the actual implantation of the pregnancy.”

    If you notice unusual pain or cramping, it’s worth noting what you’re feeling and when (you can use an app like Flo for this). This might be useful to look back and help you determine whether the cramping could be specifically due to implantation or whether it’s more likely thanks to another cause.

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    When do implantation cramps happen?

    Bear with us here, as it’s about to get science-heavy. Roughly midway through your menstrual cycle, one of your ovaries will release an egg in a process known as ovulation (you can use our online ovulation calculator to predict when yours is likely to happen). If that egg is fertilized by sperm (which happens inside the fallopian tubes), it creates what’s known as a “zygote.” 

    The zygote then moves from the tube into the uterus and eventually grows into a “blastocyst,” which is a cluster of cells. In blastocyst form, the fertilized egg attaches to the uterine lining, where it will begin to receive blood flow and nourishment from the uterus so the pregnancy can continue. This is the process of implantation

    When the blastocyst implants, the level of a hormone called human chorionic gonadotropin (hCG) gradually begins to rise. About two weeks later, a pregnancy test will be able to detect the hCG levels in your urine and will return a positive result if you are pregnant. If implantation doesn’t occur and you’re not pregnant, the uterine lining will begin to shed, resulting in a period. 

    Implantation bleeding and/or cramping will typically start one to two weeks after fertilization, which (confusingly) is around a similar time to when your period is expected to start. Because implantation does often coincide with the start of your menstrual cycle, many women often mistake implantation cramps for premenstrual cramps, which is partly why scientific evidence to prove they exist is so hard to pin down.

    What causes implantation cramps?

    The short answer is we don’t entirely know because the evidence isn’t quite there yet. However, what we can say is that — you guessed it — hormones are likely to be behind the cramps. Dr. Flanagan explains: “As it is a microscopic process, there actually is not any scientific evidence to support any way that cramping could be due specifically to implantation. However, due to increases in hormones like progesterone at the beginning of pregnancy and the beginning of a menstrual cycle, the hormone may actually be what is causing the sensation.”

    One other theory about what causes implantation cramps is that the blastocyst needs to attach to the uterus wall in order to begin receiving nutrients. Others suggest that prostaglandins (which are biochemicals that play a role in implantation with hormone-like effects that are known to be linked to pain or inflammation) might be to blame for cramps.

    Period cramps vs implantation cramps: What’s the difference?

    Because they can occur around the same time and have the same characteristics, implantation cramps can be mistaken for menstrual cramps and sometimes vice versa. If you’re experiencing bloating, breast pain, or any of the other pregnancy symptoms we mentioned earlier along with cramps at this stage, these are more likely to be premenstrual signs. That’s because the hormones that cause these symptoms in early pregnancy won’t have reached your bloodstream at the time of implantation.

    If you’re only experiencing cramps around the time of potential implantation, and you’re wondering whether you’re pregnant, you may need to wait a little longer before taking a pregnancy test to confirm your suspicions. It’s not necessarily the thing you want to hear (if you’re finding the pain of the two-week wait real), but the best way to find out is to wait and see if you get your period. If you miss it, then take a test. Your body needs time for the hCG to build up to a detectable level if you want to avoid a false negative (where the test tells you you’re not pregnant, but in fact, you are).

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    Ovulation cramps vs. implantation cramps: What’s the difference?

    Ovulation cramps and implantation cramps are — again — very similar. But there’s one big telltale difference between the two — ovulation cramps will happen around the time of ovulation (generally anywhere between day 11 and day 21 of your cycle, whereas implantation cramps (if you feel them) occur toward the end of the cycle. For help understanding what’s happening in your cycle, try using an app like Flo to keep track.

    How do I know if my cramps are implantation?

    It can be hard to know for sure if the cramps you’re feeling are caused by implantation since research and evidence around this is still so minimal. Typically, people start checking for pregnancy at the time of their expected period, so hold tight and wait to see whether that comes. If it doesn’t, there’s every chance the cramping you felt may have been caused by pregnancy.

    When to see a doctor about implantation cramps

    Most of the time, you won’t need to see a doctor if your twinges turn out to be implantation cramps — but, as with any bodily change, it’s always worth monitoring just in case. 

    “Very early cramping around the time of a missed period is not something to worry about,” explains Dr. Flanagan. “As the pregnancy progresses, ongoing cramping that becomes stronger, tends to be on one side, or is accompanied by bleeding could be concerning for other pregnancy complications such as a miscarriage or an ectopic pregnancy [a pregnancy that’s not located in the uterus].”

    If you notice that your pain becomes worse, or it’s ongoing and causing you concern, it’s never a bad idea to speak with a health care provider.

    Implantation cramps: The takeaway

    We know there’s a lot to unpack here, so let’s recap. Implantation cramps aren’t well documented or explained by scientific evidence, but we know lots of people report experiencing them. Therefore, it’s possible that cramping could be an early sign of pregnancy, but it’s also useful to note that you may be mistaking them for menstrual cramps. Knowing the other early signs of pregnancy can help you determine which kind of cramps you’re experiencing, and an at-home pregnancy test can confirm whether you’re pregnant or not.

    The good news is, in most cases, implantation cramps are mild and resolve on their own within one to three days. It’s rare that you would need to be worried, but if your cramping is severe, lasts longer than expected, or is accompanied by other troublesome symptoms (i.e., bleeding), make sure to speak with your doctor. Otherwise, wait for the pain to subside so you can enjoy this exciting time!


    Barbieri, Robert L. “The Endocrinology of the Menstrual Cycle.” Methods in Molecular Biology, vol. 1154, 2014, pp. 145–69.

    “Bleeding during Pregnancy.” The American College of Obstetricians and Gynecologists, Accessed 23 Sep. 2022.

    “Conception.” Cleveland Clinic, Accessed 23 Sep. 2022.

    “Corpus Luteum.” Cleveland Clinic, Accessed 23 Sep. 2022.

    Enciso, M., et al. “The Precise Determination of the Window of Implantation Significantly Improves ART Outcomes.” Scientific Reports, vol. 11, no. 1, June 2021, p. 13420.

    Kim, Su-Mi, and Jong-Soo Kim. “A Review of Mechanisms of Implantation.” Development & Reproduction, vol. 21, no. 4, Dec. 2017, pp. 351–59.

    Schumacher, Anne, and Ana C. Zenclussen. “Human Chorionic Gonadotropin-Mediated Immune Responses That Facilitate Embryo Implantation and Placentation.” Frontiers in Immunology, vol. 10, no. 2896, 10 Dec. 2019, doi: 10.3389/fimmu.2019.02896.

    “What Is Ovulation?” American Pregnancy Association, 24 Apr. 2022,

    Wolter, Justin M. “The Process of Implantation of Embryos in Primates.” Embryo Project Encyclopedia. Arizona State University, 2013, Accessed 23 Sep. 2022.

    History of updates

    Current version (01 November 2022)

    Medically reviewed by Dr. Barbara Levy, Clinical professor of obstetrics and gynecology, George Washington University School of Medicine and Health Sciences, UCSD Health, California, US

    Published (23 December 2019)

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