This subtle bleeding can be a sign you're pregnant, but not everyone experiences it. Learn what implantation bleeding is, when it happens, and how long it lasts.
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When you're trying to get pregnant, every one of your senses is on high alert for any nuance that you're officially a mom-to-be! So, if you see spotting, is it a sign of pregnancy implantation bleeding? And just when does implantation bleeding happen anyhow?

Here's everything you should know about implantation bleeding:

What is implantation bleeding?

In a nutshell: Implantation is spotting—light vaginal bleeding—that can occur when the fertilized egg implants in the lining of the uterus.

When does implantation bleeding occur?

"This bleeding occurs 10 to 14 days after fertilization," says Lauren Barlog, M.D., assistant professor in the Department of Obstetrics, Gynecology and Women's Health at Rutgers NJ Medical School. "It typically occurs around the time of your next expected period."

How long does implantation bleeding last?

Sometimes it's so minor that you don't even notice it—or you may think it's a super-light period. Typically, it's minimal bleeding or spotting for a day or two.

Do all women experience implantation bleeding?

Nope. Some women will, some won't. And it doesn't mean implantation didn't occur if you don't notice it.

"Women wonder if it's good to see implantation bleeding or do you hope you never see it?" says Zev Williams, M.D., Ph.D., chief of the Division of Reproductive Endocrinology and Infertility at Columbia University Medical Center. "But it's actually a diagnosis given after the fact." That means if you do see spotting, you probably won't even realize what it is (or, more accurately, what it was!) until a pregnancy test comes up positive later on.

How do I know if it's implantation bleeding or spotting?

You know what's a 'normal' period for you. If this seems 'different' or if you've been attempting to get pregnant and this is light, spotty, and lasts only a day or so, it may not be your period. But only time will tell! What to do? Wait a week after spotting, then take a pregnancy test, says Dr. Barlog.

How can I tell if it's not really implantation bleeding?

"If you are spotting but also have pain that's concentrated on one side, rectal pain, or a history of infertility or tubal disease, you should see a doctor immediately," says James Segars, Jr., M.D., director of Reproductive Science and Women's Health Research, and a professor of gynecology and obstetrics at Johns Hopkins Medicine. "These are signs that you could have a tubal or ectopic pregnancy, when the fertilized egg implants somewhere other than the uterus, usually within the fallopian tubes."

And you also should see your doctor if you've had bleeding or spotting between periods for several months because you may be dealing with other conditions such as fibroids or polyps.

How soon after implantation will you see a positive pregnancy test?

While every test has a different threshold for sensitivity, the absolute earliest you should take one is about four or five days before your next expected period, says Dr. Williams. If it's negative, repeat it in a few days.

Is there anything else about early bleeding during pregnancy I should know?

If you already know you're pregnant and notice some spotting, you may be experiencing what's called "first trimester bleeding." About 15 to 25 percent of women experience light bleeding or spotting during the first few months of pregnancy. It's usually not a cause for worry but should be monitored.

"In general, any bleeding during early pregnancy is common but not normal, and you should call your doctor," says Dr. Barlog. The good news is that in most cases with early bleeding, you'll go on to have a healthy pregnancy.