Implantation bleeding occurs when a fertilized egg attaches to the lining of a woman's uterus to start the growth process of pregnancy.

It is a normal occurrence in pregnant women, yet many women are completely unaware of what it is.

Some women may confuse the bleeding with spotting from menstruation, as the two can appear similar.

The bleeding is very light and will usually require no medical attention. In some cases, however, implantation bleeding may require a visit to a healthcare practitioner.

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A fertilized egg attached to a woman's uterus.

Implantation bleeding happens just before the expected menstrual cycle. It is a very early sign of pregnancy, occurring a few days before a pregnancy test will confirm a woman is pregnant.

The process of implantation starts with fertilization. Once a sperm has fertilized an egg, it is called an embryo.

The embryo travels through the fallopian tube towards the uterus. During this time, the embryo multiplies, becoming a blastocyst, which is a number of cells all bunched together.

Once the blastocyst reaches the uterus, it will look for a good spot to attach itself to the wall of the uterus. This attachment to the uterus is called implantation. Once implantation is complete, the embryo will remain in the same spot throughout the 9-month journey to becoming a newborn.

Implantation usually occurs about 1 to 2 weeks after the egg has been fertilized. This is also around a week after ovulation and a few days before a woman has her regular period.

Implantation bleeding is one of the earliest easily identifiable signs of pregnancy.

There are some distinct signs and symptoms to help women identify implantation bleeding:

  • Early bleeding: Implantation bleeding will often occur a few days before the expected menstruation cycle. This is not always the case, however, and many women confuse the two.
  • Unusual colored discharge: Implantation bleeding produces an unusual discharge that varies in color from pinkish to very dark brown or black.
  • Very light bleeding: Bleeding and discharge caused by implantation usually last no more than 48 hours. Many women experience just a few hours of spotting or one spot or streak of discharge.
  • Cramping: Implantation can also cause mild and temporary cramps.

Other signs

As implantation is an early sign of pregnancy, a woman may also experience other pregnancy-related symptoms. Early signs of pregnancy can vary from woman to woman and may include:

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Implantation bleeding may happen before the menstrual cycle.
  • mood swings
  • tiredness
  • dizziness
  • headaches
  • tender, swollen breasts
  • nausea and vomiting
  • constipation
  • increased sense of smell
  • food cravings and aversions
  • a raised body temperature

Implantation bleeding is a normal sign of pregnancy and is not usually dangerous. Because of this, there is no need for treatment.

Bleeding caused by implantation usually clears up within a couple of days with no treatment necessary. Abnormally heavy bleeding may be a sign of menstruation or a pregnancy complication. Doctors recommend that women do not use tampons during this time.

Many women confuse implantation bleeding with a light menstrual cycle. There are a few steps women can take to help them identify what is happening:

Inspect the blood

First, the blood itself can provide some answers. Implantation bleeding will usually look different from menstrual bleeding. It may be darker than period blood due to the extra time it takes for the blood to travel through the vagina.

The amount of bleeding is usually very light as well. Implantation bleeding usually lasts no more than 1 day. In some cases, women may experience a few hours of spotting and nothing more. Some women may experience a single spot of blood and discharge with no other signs. It will often produce a discharge with a pink or brownish tint.

Menstruation usually produces blood with more of a red color that lasts a few days or more, with discharge ranging from heavy to light during that time.

Most women understand what their normal blood flow looks like and would likely notice that implantation bleeding looks different.

Check the timing

Any woman who suspects that she is experiencing implantation bleeding should think of the timing since she last had sex.

Implantation occurs from 6 to 12 days after fertilization and around a week after ovulation. This puts it near or just before the time of menstruation in most cases. If it has been more than a month since a woman has had sex, she is unlikely to be experiencing implantation bleeding.

The easiest way to find out is to wait a few days and then take a home pregnancy test. These tests work best a few days after implantation bleeding has stopped.

Check for other symptoms

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Morning sickness is a symptom that may help a woman identify implantation bleeding.

Associated pregnancy symptoms may also help women to identify the difference between implantation bleeding and menstruation.

One easily identifiable symptom is morning sickness. A feeling of nausea first thing in the morning may be a sign of pregnancy and is usually not a sign of regular menstruation. This nausea may also be triggered by certain everyday smells, such as meat, garlic, or pets.

Another symptom caused by implantation is cramping, which occurs as the egg attaches to the wall of the uterus. These cramps are often very light compared with those that many women experience during a regular period.

Tenderness in the breasts may also be a sign of pregnancy, especially in women who do not experience breast soreness during menstruation.

Other symptoms may be harder to gauge, such as mood swings and food cravings. These can be a sign of both pregnancy and premenstrual syndrome (PMS).

Implantation bleeding is not a cause for concern most of the time. It is a sign of the uterus making way for an embryo to begin its growth.

Women who are still uncertain about whether they have experienced implantation bleeding or a period can take a pregnancy test to find out if they are pregnant. Women should wait a few days after the bleeding has stopped before taking the test, however.

Experiencing heavy bleeding during any stage of pregnancy is a sign of a complication and women should seek medical attention.

When to see a doctor

Light bleeding during various stages of pregnancy is normal. It can be caused by a variety of things, such as irritation from a routine exam, sex, or a vaginal infection. This light bleeding does not usually last long, but women who experience any bleeding should report it to a doctor, just to be safe.

A woman who experiences heavier bleeding will require medical attention. A heavy or persistent blood flow that is accompanied by menstrual cramps or blood clots may be a sign of serious complications, such as:

  • a molar pregnancy, where a noncancerous tumor develops in the uterus
  • an ectopic pregnancy, where the egg implants somewhere other than the uterus, is a medical emergency
  • a miscarriage, which is the early loss of a pregnancy