Pregnancy What Is Implantation Bleeding? By Rachel Macpherson Rachel MacPherson is a health writer, certified personal trainer, and exercise nutrition coach based in Montreal. Learn about our editorial process Rachel Macpherson Medically reviewed by Medically reviewed by Monique Rainford, MD on March 18, 2021 Monique Rainford, MD, is board-certified in obstetrics-gynecology. She is the chief of obstetrics and gynecology at Yale Health. Learn about our Medical Review Board Monique Rainford, MD Updated on July 06, 2021 Print Table of Contents View All Table of Contents Types Purpose Signs Complications Implantation bleeding occurs when a fertilized egg attaches itself to the uterine lining (endometrium). Implantation is typically six to 12 days after fertilization and can cause some spotting or light bleeding, although this is not always the case. Approximately 15% to 25% of those who become pregnant will experience bleeding in the first trimester. Implantation bleeding is a normal symptom that doesn’t require any medical attention. However, there are important signs to watch for in case of something more serious. Demkat / Getty Images Types There are various reasons why you might see bleeding, including the beginning of your period. You may even assume implantation bleeding is the start of your period since the timing of both are similar. Many of the signs of implantation are similar to your menstrual cycle, so it might be difficult to know if you are pregnant unless you have missed a period. The three types of bleeding related to your cycle and/or pregnancy are: Implantation bleeding: When a fertilized egg attaches itself to the uterine lining (endometrium). Ovulation bleeding: Light bleeding or spotting that occurs when an egg is released from the ovary. Period bleeding: If a fertilized egg does not implant in the wall of your uterus after ovulation, the lining sheds. Timing of Bleeding Implantation Bleeding 20 to 24 days Ovulation Bleeding 14 days Period Bleeding 28 days *Based on a 28-day cycle Early miscarriage can also cause bleeding and occurs in about 10% of known pregnancies. Unlike the other causes of bleeding, early miscarriage typically causes heavier, darker blood flow and cramping, with visible tissue and blood clots passing through the vagina. The pain and bleeding of miscarriage can be greater than during your period. Early miscarriage can occur five weeks after ovulation. Symptoms of Miscarriage Two major symptoms of a miscarriage are: Vaginal bleeding Abdominal cramping If you experience pain or cramping with or without bleeding and you think you might be pregnant, seek emergency care. Bleeding can also occur during an ectopic pregnancy—when a fertilized ovum implants outside of the uterus. Symptoms of an Ectopic Pregnancy Symptoms of an ectopic pregnancy include: Bleeding Cramps on one side of your body, ranging from mild to severe Call for emergency care if you suspect an ectopic pregnancy or experience pain. Cervical erosion, also called cervical ectropion, can also cause light bleeding or spotting. The cervix has an increased blood supply during pregnancy and can sometimes bleed, which is typically harmless. This bleeding can happen as a result of the cervix being irritated during a pelvic exam. Sometimes this happens after sexual intercourse, which you should speak to your doctor about. Cervical ectropion can also happen when you are not pregnant. It is a condition in which the cervical canal turns outward, exposing the cervix’s inner cells to the vaginal canal’s acidic environment, causing it to become red, raw, and potentially bleed. Cervical ectropion is a normal physical anomaly that people are born with. Hormonal changes can cause it, making it more likely during adolescence, pregnancy, or when taking an estrogen-containing contraceptive like the pill. Several other causes of bleeding not due to pregnancy include: Fertility treatments such as IUI or IVF procedures Sexual intercourse Endometriosis Beginning, ending, or missing doses of hormonal contraception Fertility drug side effects Diseases of the thyroid Polycystic ovary syndrome (PCOS) Fibroids or polyps Infections Ovulation Menstruation Cervical ectropion Purpose When an egg is released from an ovary, usually once per month, ovulation occurs. At this point, the egg travels through the fallopian tube. If an egg is penetrated by a sperm and becomes fertilized due to intercourse, it starts to divide into multiple cells while moving through the fallopian tube to the uterus. A fertilized egg takes several days to travel down the fallopian tube before either implanting or being shed by the body if implantation fails. If it does implant, human chorionic gonadotropin (hCG) hormone is produced in the uterus, preventing the uterine lining from being shed. If implantation does not occur, the egg and uterine lining are shed during the menstrual period. After dividing into about 100 cells, the egg becomes what is known as a blastocyst. The uterine lining has many blood vessels, so when the fertilized egg (blastocyst) pushes into the lining, bleeding can occur. This blood will exit through your cervix, just like menstrual flow. Signs Implantation bleeding is one of the earliest signs of pregnancy and occurs around the same time you would be expecting your period. Since these two causes of bleeding can be confused, the best way to know for sure if you are pregnant is by taking a pregnancy test. It’s important to note that many people may not experience any bleeding at all in early pregnancy. If you are pregnant, your body will increase human chorionic gonadotropin (hCG) production, which a test can detect. However, there are differences between menstrual blood flow and implantation bleeding. Some signs of implantation bleeding are: Light pink to rust-colored spotting, light bleeding, or pink-colored discharge May come and go, or remain constant Can last hours or a few days Light cramping Headache Nausea Lower backache Mood change Breast tenderness Complications Implantation bleeding is normal and not a risk factor. If bleeding occurs more than a few days after you expected to get your period, it will not likely be implantation bleeding. If the bleeding is heavy, constant, or lasts for several days, it is almost certainly not from implantation and should immediately be checked by a doctor. When to See a Doctor Visit your doctor about irregular or unexpected vaginal bleeding. A Word From Verywell Bleeding when suspecting a pregnancy can be alarming, but implantation bleeding is a common and normal early pregnancy sign. It may be difficult to tell if the bleeding you experience is from implantation, your period, or another cause. Be sure to tell your doctor about any bleeding you experience if you believe you may be pregnant, and seek emergency care if you experience abnormal heavy bleeding or pain if you know you are pregnant. Was this page helpful? Thanks for your feedback! Sign up for our Health Tip of the Day newsletter, and receive daily tips that will help you live your healthiest life. Sign Up You're in! Thank you, {{form.email}}, for signing up. There was an error. Please try again. What are your concerns? Other Inaccurate Hard to Understand Submit Article Sources Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy. American College of Obstetricians and Gynecologists. Bleeding during pregnancy. 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