Implantation Bleeding or Period?

Let’s take a deep dive into implantation bleeding and other early signs of pregnancy. 

By Dr. Mare Mbaye, OBGYN

We all know the basics of how conception works: have vaginal sexual intercourse, wait for the sperm and egg to join and create an embryo, the embryo grows into a fetus, and voila, hello baby! While this may appear to be a simple process, there’s so much more at play here. Let’s fill in the gaps in human reproduction a bit, starting with when the sperm meets the egg.

What Is Implantation? 

Maybe you remember the word “implantation” from your high school sex ed classes years ago but are a little fuzzy on what it means now. Implantation refers to the fertilized egg (or embryo) burrowing into the uterine lining, where it can safely grow, about 7-10 days post-fertilization. [1]

Through a complex system of hormonal signals between the female reproductive system and the brain, the body cyclically grows the uterine lining (endometrium) that would be needed to support a pregnancy. [1-2] When you’re not pregnant and are on your period, you’re shedding the uterine lining that your body had prepared for the fertilized egg. [2] 

Implantation Bleeding

Many women experience “implantation bleeding” when the fertilized egg implants. It happens because a small portion of that uterine lining might detach and shed during the process of implantation. [3] 

It can be confusing because it looks very similar to a light period—it’s spotting right around the time when you usually would get your period. Given this light bleeding, you might understandably think that you’re not pregnant. However, one distinguishing factor that may help is that implantation bleeding should be much lighter in quantity than your normal period. [3] Read Can Implantation Bleeding Be Heavy? for more information

When Does Implantation Spotting Happen?

Implantation bleeding is totally normal and nothing to be concerned about. [3] As we said above, it generally happens 6-12 days post-fertilization, or around the time of your expected period. [1,3] If you are beyond that timeframe, it is not likely implantation bleeding. There are other types of vaginal bleeding that can happen during pregnancy. [4] In fact, about 20% of women have some bleeding during the first 12 weeks of pregnancy. [4] If you are already pregnant and experiencing vaginal bleeding, talk to your doctor. 

Symptoms of Implantation

Other common signs of implantation can include: light cramping (like the bleeding, it’ll feel like what you experience with a regular period, but less intense), mood swings, breast tenderness, nausea and pain in your lower back. [1,3] Many of these symptoms result from the higher levels of progesterone circulating in your body, which increases to help support the pregnancy (just remember that pro-gesterone is pro-gestation). [3] Keep in mind, these symptoms can be similar to premenstrual syndrome (PMS) or other symptoms that occur between ovulation and a period (known as the luteal phase). 

Implantation Bleeding or Period?

The bottom line here? If you don’t know about the signs of implantation beforehand, you might just think you’re having an unusually light period. While first trimester miscarriages are common, occurring in 10% of all clinically recognized pregnancies, spotting and light episodes are not associated with a higher risk of miscarriage, especially if they only last one to two days. However, if you have heavy bleeding, particularly if accompanied by pain, that is associated with a higher risk of miscarriage and you should see your provider.

Spotting that turns into heavier bleeding may also just be your period, however, you should always speak with a provider if you are concerned something else is going on. 

Testing for Pregnancy

A pregnancy test can often help you in figuring out what’s happening. Implantation cues the 

production of a pregnancy hormone called human chorionic gonadotropin (hCG), which an at-home pregnancy test detects in urine as soon as three to four days after implantation. By seven days post-implantation (the time of the expected period), 98% of tests should be positive. [5-6] 

However, taking the pregnancy test too soon—either before implantation has happened or when the hCG levels aren’t high enough for a pregnancy test to detect them yet—can result in a false-negative result. If you think you could be pregnant but a pregnancy test is showing a negative result before your expected normal period, it’s worth trying again anywhere from a few days to a week later to see if anything changes.

Once you get a positive pregnancy test, you’ve passed a major milestone: you were able to get pregnant! This is a big feat in and of itself if you consider that only 15 – 20% of healthy people under the age of 35 get pregnant during a month of trying to conceive with vaginal intercourse. [7] 

There are a few things you’ll want to think about now: call your OBGYN office to see when they recommend scheduling a prenatal visit. Six to eight weeks into a pregnancy is usually the preferred time frame since that is one of the best times to confirm pregnancy by ultrasound. This ultrasound is used to identify your due date and to confirm that implantation occurred in the uterus and not in one of the fallopian tubes or another site in the abdomen—an emergency situation called an ectopic pregnancy. 

Preparing for Pregnancy With Natalist

If you are hoping to conceive soon, make sure you’re taking your daily prenatal vitamins and you prioritize healthy lifestyle habits, like not smoking or drinking and eating healthy, nutritious foods. You can learn more about your cycle and reproductive health by testing vital hormones. This includes ovulation testing, or testing hormones like estrogen, progesterone, testosterone, and others that can influence your ability to conceive. Natalist is proud to offer a wide range of products, from supplements to self-care items. Browse here, or keep reading about TTC! 

Sources:

1. Kim SM, Kim JS. A Review of Mechanisms of Implantation. Dev Reprod. 2017;21(4):351-359. doi:10.12717/DR.2017.21.4.351
2. Thiyagarajan DK, Basit H, Jeanmonod R. Physiology, Menstrual Cycle. [Updated 2022 Oct 24]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK500020/
3. Implantation Bleeding. Cleveland Clinic. December 2022. https://my.clevelandclinic.org/health/symptoms/24536-implantation-bleeding
4. Everett C. Incidence and outcome of bleeding before the 20th week of pregnancy: prospective study from general practice. BMJ. 1997;315(7099):32-34. doi:10.1136/bmj.315.7099.32
5. Wilcox AJ, Weinberg CR, O'Connor JF, et al. Incidence of early loss of pregnancy. N Engl J Med. 1988;319(4):189-194. doi:10.1056/NEJM198807283190401
6. Chard T. Pregnancy tests: a review. Hum Reprod. 1992;7(5):701-710. doi:10.1093/oxfordjournals.humrep.a137722
7. Mosher WD, Pratt WF. Fecundity and infertility in the United States: incidence and trends. Fertil Steril. 1991;56(2):192-193.

Originally published 07/31/2019. Updated for accuracy and relevancy on 12/15/2023. 

Dr. Marieme Mbaye is a Medical Advisor at Natalist, a Fellow of the American Congress of Obstetricians and Gynecologists (FACOG), and Medical Director at Noula Health. She previously worked as a private practice OBGYN in NYC. She has several years of experience in digital health as a medical advisor, consultant, and content creator. She received her MD from the University of Tennessee Health Science Center, and her BS from Yale University.