Implantation Bleeding: Everything You Need To Know (2024)

Not every pregnant person will experience this symptom, but for some people, a fertilized egg attaching to the lining of the uterus can cause a small amount of bleeding, which is referred to as implantation bleeding. Implantation bleeding tends to occur one to two weeks after fertilization, according to the American College of Obstetricians and Gynecologists (ACOG).

“Whether conception occurs in the fallopian tube or invitro in a lab, implantation in the endometrium [the lining of the uterus] occurs six to 10 days after fertilization,” says Shari Lawson, M.D., assistant professor of gynecology and obstetrics at the Johns Hopkins University School of Medicine in Baltimore.

She adds that the endometrium is rich in nutrients and proteins, which are supplied by a network of vessels called the spiral arteries. “When implantation occurs, a small amount of bleeding may arise from the spiral arteries.”

While confusing and even alarming, implantation bleeding is not uncommon and is usually not cause for concern.

Implantation bleeding typically happens about 10 to 14 days after conception, which is also around the time when a person expects their period to arrive, according to Dr. Lawson.

How Long Does Implantation Bleeding Last?

While a typical period lasts between two and seven days, according to the ACOG, implantation bleeding will typically not last as long, says Dr. Lawson. Instead, it usually lasts just a few days, which is the time it takes for the egg to implant into the uterine lining. That being said, everyone is different, so some people will experience implantation bleeding that lasts a bit longer.

Implantation bleeding is not a rare occurrence. “It occurs in between 10% and 20% of pregnancies,” says Dr. Lawson.

Bleeding that’s not related to implantation is somewhat common in the first trimester as well. The cervix will sometimes bleed because more blood vessels are developing in the first trimester, and light spotting or bleeding can occur after sexual intercourse or a vagin*l exam.

Overall, bleeding in the first trimester—implantation-related or not—may occur in up to 25% of pregnancies, according to the ACOG^[1]Bleeding During Pregnancy. The American College of Obstetricians and Gynecologists. Accessed 9/17/2021. .

Implantation bleeding is often characterized as light spotting 10 to 14 days after conception (or the fertilization of an egg by sperm). This may be around the time you expect your period to occur, potentially making it difficult to determine whether you’re experiencing implantation bleeding or your period.

While we dive deeper into the differences between implantation bleeding and a period below, generally, implantation bleeding may be more brown or pink in color (as opposed to red).

How Heavy Is Implantation Bleeding?

Implantation bleeding tends to be light in flow—lighter than your typical period—and may resemble spotting or a light period. It stops on its own and does not require treatment. Not everyone experiences implantation bleeding.

Many people might be confused by getting a positive pregnancy test while simultaneously experiencing bleeding. Or maybe you haven’t yet taken a pregnancy test, and you’re wondering if you actually have your period.

While the easiest way to find out if you’re pregnant is to take a test, other signs can indicate that you’re dealing with implantation bleeding instead of a period. For instance, implantation bleeding will probably look a bit more like spotting, or very light bleeding.

“A menstrual period is usually much heavier than implantation bleeding because a period occurs when there is synchronous shedding of the entire endometrium following withdrawal of progesterone as the corpus luteum degenerates,” says Dr. Lawson. “The corpus luteum is a cyst in the ovary that forms after ovulation and produces progesterone.”

Another factor to pay attention to is the color of the blood, she adds. While blood from a period is usually bright red, especially on heavier days, the blood you see from implantation bleeding is more likely to be brown or pink in color.

The pregnancy hormone human chorionic gonadotropin (hCG)—which is the hormone at-home pregnancy tests detect—is produced soon after implantation occurs and increases rapidly after you become pregnant. While many pregnancy tests claim accurate results even days before your missed period, the U.S. Department of Health and Human Services says waiting until the first day of your missed period will yield a more accurate result.

Even further, other experts recommend waiting up to a week after your expected period to minimize the chance of a false result.

For the most part, implantation bleeding is nothing to worry about and will resolve on its own in a few days. But there are signs to watch for that can signal it’s time to call your doctor.

“If you have a confirmed pregnancy and your implantation bleeding gets heavier or you have pain, you should contact your doctor, as it could be a sign that something is wrong,” says Dr. Lawson, adding that any out-of-the-ordinary bleeding, pregnancy-related or not, can be a reason to talk to a medical professional.

“If you ever have abnormal bleeding, which is characterized by bleeding longer than seven days, bleeding in between periods, an usually light period, a missed period or bleeding after sex, you should contact your doctor,” she adds.

While implantation bleeding is one of the more unsettling early pregnancy symptoms, it can be a common occurrence for a lot of pregnant people. But if you’re ever concerned about bleeding, or if it’s heavier than you think it should be, don’t hesitate to contact your doctor.