Anniversary rules: what are they?

The absence of a menstrual period often puts women on the trail of pregnancy. So when they think they're pregnant, but discover bleeding, they panic! What if it's an anniversary period? Never heard of this phenomenon? Elie Lingerie gives you a refresher course.

What is a menstrual period?

Anniversary periods occur when a pregnant woman has bleeding at the start of pregnancy. In reality, this is metrorrhagia, unexpected bleeding that can occur between periods, during pregnancy or at menopause. It affects 1 in 4 pregnant women.

Why do women menstruate during pregnancy?

Women don't menstruate when they're pregnant. In fact, menstruation is due to the elimination of the uterine lining (the endometrium) when the egg has not been fertilized. Anniversary periods are generally artificial menstrual bleeding, as is the case with women taking the pill. This bleeding may be caused by a decidual hematoma, a slight detachment of the placenta that will reabsorb on its own. It can also be caused by discharge from weakened vaginal walls. The cervix is more vascularized during pregnancy. Harmless bleeding may occur after a gynaecological examination or sexual intercourse.

When is an anniversary period?

Contrary to what the term "anniversary period" might suggest, this bleeding does not necessarily occur when your period should have arrived. They can occur throughout the first six months of pregnancy. In the case of pregnancy denial (the pregnant woman is unaware that she is pregnant), the duration of anniversary bleeding varies. If the woman continues to take the pill, the contraceptive may continue to cause artificial menstruation.

How can I recognize the onset of an anniversary period?

The most important issue with anniversary periods is how to recognize them. There are a number of signs that can put you on the right track.

A change in color

Every woman's period has a different color. However, red bleeding should alert you. Brownish or blackish discharge is also worrying, especially if accompanied by pain. When discharge is slightly pinkish, there's a good chance it's an anniversary period.

The onset of pain or cramps

Anniversary periods are generally painless. Occasionally, however, you may experience cramps or tightness. If you experience painful blood loss, consult your doctor as soon as possible. This may be a sign of miscarriage or ectopic pregnancy.

Reduced menstrual flow

Anniversary periods last from one to two days. This bleeding is not heavy.

Bleeding caused by implantation

When the fertilized egg settles on the uterine lining, this is called implantation. This occurs around 10 days after fertilization, which is around the time when menstruation should have occurred. Nidation sometimes causes bleeding, which may explain the "anniversary period".


Pregnant women generally rely on their periods to tell them if they're pregnant. However, if their egg is fertilized and implantation causes anniversary periods, they may not be able to detect their pregnancy. When you have your period (or think you're having your period) and feel nauseous, take a test to see if you're pregnant.

Is blood loss always linked to anniversary periods?

Blood loss during the first trimester of pregnancy is not necessarily linked to an anniversary period. Bleeding in pregnant women should always be reported to a doctor. It may be a sign of complications such as ectopic pregnancy, miscarriage or molar pregnancy (abnormal development of the placenta).

How can you tell the difference between anniversary periods and miscarriage?

A heavy period lasting more than two days, or a bright red color, could be a sign of miscarriage. On the other hand, pain such as cramping or tugging is not necessarily a sign of miscarriage, and can occur during an anniversary period.

Is it possible to have a negative test during an anniversary period?

It's perfectly possible to have an anniversary period after a negative test. In early pregnancy, tests are unreliable. If you experience nausea and breast tenderness, but your test is negative, your period may be an anniversary period resulting from nesting. Only a blood test will give you a reliable result.

Bleeding during pregnancy is always worrying, but it can be harmless. Such is the case with anniversary periods, which can occur during the first trimester of pregnancy. To make sure you're suffering from this phenomenon, which has no impact on your pregnancy, consult your doctor. Heavy periods, or periods accompanied by fever or pain, may conceal a miscarriage.

Anniversary periods FAQ

How can I tell the difference between an anniversary period and bleeding?

Anniversary periods are light in color. Bright red or blackish bleeding is more likely to suggest a miscarriage. Similarly, heavy periods are rare. A heavy flow lasting more than 2 days may indicate a problem with the pregnancy. Acute pain or a fever over 38.5°C should also alert you and prompt you to seek medical advice.

What is the color of bleeding during pregnancy?

Anniversary bleeding is light pink in color. They may be slightly brown or red, but should not be accompanied by pain or fever. To be sure it's an anniversary period, consult a doctor.

Is it possible to be pregnant and bleed?

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