When you’re actively trying to get pregnant, those two weeks between ovulation and a positive pregnancy test (or your period) can seem much longer. If you’re like most women, you’ll spend them hyper-aware of every ache, twinge and craving your body has, wondering whether it’s an early sign of pregnancy.
While it can be hard to tell, many women who go on to have healthy, normal pregnancies have what’s called implantation bleeding around the time that their embryo lodges itself into the side of the uterus.
What is implantation bleeding?
After ovulation and at the moment an egg is successfully fertilized by a sperm in a fallopian tube, the embryo starts dividing and growing. At this time, the inner lining of the uterus, called the endometrium, starts to change. It's already been thickening throughout the menstrual cycle, but it’ll need to grow and mature even more to protect and nourish an embryo.
Around five to six days after fertilization, the quickly growing embryo has moved down the fallopian tube and into the uterus. It’s starting to need more nutrients, and the endometrium has filled in enough to support it.
Next, the embryo attaches itself to the endometrium, where it becomes reliant on a mother’s body — for the first time — for nutrients and oxygen. When the embryo implants, it can disrupt tiny blood vessels in the spot it burrows into. This won’t cause any problems (the endometrium recovers!) but some women will experience light bleeding, from pinkish or red to brown discharge.
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When does implantation bleeding happen?
Implantation bleeding will likely arrive earlier than your expected monthly menstrual period, usually around seven to 10 days after fertilization or conception.
Signs of implantation bleeding
These are some of the most common implantation bleeding symptoms:
- Light bleeding or spotting that some women say is different from normal period bleeding because the blood is darker
- Mild cramping
- A woozy feeling
- Swollen breasts
How long does implantation bleeding last?
Implantation bleeding usually only lasts one or two days.
Implantation bleeding vs. period bleeding: How to tell the difference
Since implantation bleeding is a symptom that can often occur before you test positive on a pregnancy test, it can be hard to know whether light bleeding is an early sign of pregnancy or just normal spotting leading up to your period. And unfortunately, there’s no conclusive way to find out.
The best way to know whether you’re pregnant or not is to wait a few more days and take a pregnancy test. The timing of when you last had sex might also help you figure it out. If it’s been more than two weeks, it’s unlikely that any spotting you're having is implantation bleeding.
About a third of women who report having experienced implantation bleeding often describe it as distinct from their usual premenstrual spotting — some say the blood is darker and not as red compared with normal period blood. Others have mild cramping at the same time as the spotting.
But for many women, the two types of bleeding aren’t different at all. So you’re not alone if you assume that some spotting is implantation bleeding and get your period a few days later, or if you assume that implantation bleeding is normal spotting and end up being pregnant!
When to call the doctor
Light bleeding during pregnancy — even at times other than implantation — is often normal. Causes can include mundane things like irritation of the cervix following a pelvic exam, sex or infection of the vagina.
But because bleeding following a positive pregnancy test can sometimes be a sign of ectopic pregnancy, molar pregnancy or other early miscarriage, you should always call your medical provider if you experience it so you can talk through any other symptoms. Try not to worry too much though. Chances are good that if the bleeding is light and doesn't last long, everything is fine.
Frequently asked questions
How do I know if it's implantation bleeding?
Light bleeding or spotting, mild cramping, a woozy feeling, swollen breasts and headaches are some commonly reported symptoms associated with implantation bleeding.
What does implantation bleeding look like?
Implantation bleeding is light bleeding or spotting. Some women say the blood looks darker than it does during their period.
How long can implantation bleeding last and how heavy can it be?
Implantation bleeding usually only lasts one or two days and is typically light bleeding.
Can I take a pregnancy test during implantation bleeding?
The best way to know whether you're pregnant or not is to wait a few more days before taking a pregnancy test. (For best results, take a pregnancy test the day you expect your period.)