Can implantation bleeding be heavy?
No, implantation bleeding isn't heavy. The bleeding is typically light – just a little spotting – and light in color, too (pinkish or brown, rather than dark red like menstrual blood).
Implantation bleeding happens when a fertilized egg implants in the blood-rich lining of the uterus, causing blood vessels to burst. This can happen a week or two after fertilization.
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"Approximately 10% of women experience some sort of bleeding two weeks after fertilization," says Shannon Smith, M.D., an obstetrician and gynecologist at Brigham Faulkner Ob/Gyn AssociatesOpens a new window in Boston and member of the BabyCenter Medical Advisory Board. "This bleeding is usually very light, like spotting, and distinctly different from a menstrual period."
If you're starting a pregnancy, you may have other mild implantation symptoms, such as implantation cramps, nausea, breast tenderness, lower back pain, mood swings, or headaches.
Or, if you're having spotting with a progressively heavier flow, you may have started your menstrual period.
Rarely, because of an underlying bleeding disorder that affects the blood's ability to clot, a woman may bleed more than usual during implantation (or any other time, such as during her period or when she's injured).
What else could be causing bleeding in early pregnancy?
According to the American College of Obstetrics and Gynecology (ACOG)Opens a new window, bleeding or spotting in early pregnancy is common and in most cases doesn't signal a major problem. Because more blood vessels are developing in the cervical area, it may be prone to bleeding. For example, you may experience bleeding when you have a Pap test or pelvic exam, or after sex.
Other reasons you may have bleeding early in pregnancy include:
- An ectopic pregnancy. This means that the fertilized egg has implanted outside the uterus, most often in a fallopian tube. Bleeding can happen when the fallopian tube ruptures. Symptoms include low back pain, mild cramping on one side of the pelvis, or abdominal, pelvic, or shoulder pain. An ectopic pregnancy is a medical emergency.
- Molar pregnancy. A molar pregnancy is when a problem with chromosomes causes the growth of cysts rather than the development of an embryo or placenta. It can cause vaginal bleeding, as well as nausea and vomiting, a swollen stomach, and pelvic pain.
- Early pregnancy loss. Miscarriage happens in about 10% of known pregnancies, and spotting or bleeding (with or without pain) is the most common sign. The bleeding may be pink, bright red, or brown, and there may be blood clots.
- Subchorionic hematoma. This condition happens when the outer layer of the amniotic sac (chorion) separates from part of the uterine wall, causing blood to pool. Subchorionic hematoma is the most common cause of vaginal bleeding in patients who are 10 to 20 weeks pregnant.
- Infection. A sexually transmitted infection (STI) such as chlamydia or trichomoniasis, or other infections such as bacterial vaginosis (BV) or a yeast infection, can cause bleeding in early pregnancy. To protect your pregnancy and baby, it's important to treat any of these infections while you're pregnant.
- Hormones. Hormonal changes due to birth control pills or polycystic ovary syndrome (PCOS) can cause irregular bleeding, especially mid cycle. Ovulation bleeding can also show up mid cycle, when estrogen levels dip and progesterone levels start to rise. This is uncommon, though. According to one studyOpens a new window of menstrual bleeding patterns published in the American Journal of Epidemiology, less than 5% of women experience mid-cycle bleeding.
- Uterine fibroids and polyps. These are noncancerous growths that develop in the tissue of the uterus. If the placenta implants close to the fibroid, the chances of bleeding in early pregnancy increase to 60%, according to a studyOpens a new window published in Obstetrics & Gynecology.
- Bleeding disorder. Women with a bleeding disorder such as hemophilia or von Willebrand disease (VWD) can experience heavy vaginal bleeding. (Typically this would have caused heavy periods or other bleeding problems before pregnancy, too.)
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When to call your doctor
While bleeding in early pregnancy usually doesn't mean something is wrong, it can signal a serious problem such as an ectopic pregnancy.
Call your doctor or midwife if you have unexpected bleeding (other than your period or light implantation bleeding). Note the color of the blood (light or dark, brown or bright red) and how heavy it is, so you can share this information with your provider.
If you're having heavy bleeding, get immediate medical care: Call 911 or go to the ER if you can't get in touch with your provider. Also get immediate care if you have bleeding along with dizziness, stomach or pelvic pain or cramping, or symptoms of an ectopic pregnancy, such as shoulder pain.
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