Implantation Bleeding vs Period

This is a common question from women while trying to conceive. Luckily for us there are some differences. Let’s start with the basics.

What is Implantation Bleeding

Implantation bleeding is bleeding that sometimes occurs as the embryo implants in the inner lining of the uterus (endometrium).

However, for most women embryo implantation does not cause any visible bleeding. In fact, less than 10% of women have vaginal bleeding during the window of implantation.

Moreover, this bleeding could also be intermenstrual luteal bleeding that happens sometimes and not actually implantation bleeding.

Unfortunately, differentiating between the two according to color and flow alone is not possible.

Signs of Implantation Bleeding

Early symptoms or signs of implantation bleeding include:

• Raised basal body temperature
• Abnormal cervical mucus
• Breast changes
• Fatigue
• Mood swings

When does Implantation Bleeding Happen

Implantation bleeding occurs during implantation of the embryo in the uterus, approximately 6 to 10 days after ovulation and unprotected intercourse. This usually means light bleeding sometime between cycle days 20 and 24.

However, ovulation often occurs several days later than textbook (cycle day 14) for many women. This delays implantation and may result in implantation bleeding around the same time as expected menstruation (cycle days 27 to 31).

This can be confirmed with a sensitive pregnancy test as hCG levels should have begun to rise significantly around this time.

How Long does Implantation Bleeding Last

Implantation bleeding can last anywhere from 1 to 6 days for women who experience vaginal bleeding after trying to conceive.

Implantation Bleeding and Pregnancy Tests

A positive pregnancy test is possible just a few days after implantation bleeding begins.

While a negative pregnancy test, a few days after implantation bleeding begins, indicates either normal menstrual bleeding or very early pregnancy loss. Unfortunately, both types of bleeding are practically indistinguishable from each other based on bleeding pattern alone.

Implantation Bleeding vs. Miscarriage

Bleeding associated with miscarriage is usually heavier and longer (> 1 week) than implantation bleeding. The bleeding from miscarriage may also contain clots and tissue from the uterus if implantation was partially successful. This bleeding may be accompanied by lower abdominal cramping.

Unfortunately, the majority of early miscarriages are not detectable with at home pregnancy tests (i.e. 8/10 early miscarriages). This is most likely a result of delayed implantation. As Wilcox et al. reported the risk of early miscarriage increases significantly with each day implantation is delayed after the 9th day post ovulation.

Research suggests tracking hormone levels, especially oestradiol, after ovulation can predict women at risk of early miscarriage and be used to differentiate between implantation bleeding or miscarriage.

When to See a Doctor

Although bleeding during implantation is usually not a cause for concern, it could be serious if you experience:

• Intermenstrual bleeding previously (before trying to conceive)
• Bleeding during or shortly after sex
• Pain or discomfort
• Further bleeding after a positive pregnancy test

This could be signs of an underlying condition (infection, polyps, fibroids, luteal phase defect, endometriosis, cancer) or a developing medical condition, such as miscarriage or ectopic pregnancy, which requires immediate medical attention.

A Final Word from Fertility SCIENCE

As you can see, telling the difference between implantation bleeding and other causes of bleeding is challenging.

A pregnancy test sometime about the 3rd week post ovulation is simplest way to confirm your bleeding is pregnancy related.

Even if the test is negative and you suspect early pregnancy loss, don’t be alarmed. It happens in almost 25% of cases and is the bodies natural way of managing quality issues. In fact, experts consider it a sign of normal fertility. Wilcox et al. reported that almost every woman with early pregnancy loss (≥95%) went onto become pregnant in the following 1 to 2 years.

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