Implantation Bleeding

Definition - What does Implantation Bleeding mean?

Implantation bleeding is mild bleeding that occurs in very early pregnancy and is thought to attributed to the burrowing of a fertilized egg into a uterus. This is interpreted by some to be an early sign of pregnancy.

Implantation of a fertilized egg into the uterus generally starts seven days after ovulation, with the egg completely burrowed within the uterine lining by day nine. One small study indicates bleeding in very early pregnancy is most likely to occur five days after implantation.

Implantation bleeding may be referred to as early pregnancy bleeding.

FertilitySmarts explains Implantation Bleeding

Studies on bleeding in very early pregnancy have not been able to confirm the original hypothesis that early bleeding in early pregnancy is a sign of implantation, stemming from a 1954 study.

One study showed 9% of pregnancies reporting bleeding in the first eight weeks of pregnancy. Reported bleeding was typically light, requiring one or two pads or tampons in a 24 hour period. Bleeding that stops and then resumes is more likely to be detrimental to an ongoing pregnancy.

It is possible that bleeding is the result of drop in levels of progesterone that may occur during the time period when the hormone stops being produced by the corpus luteum and when the placenta takes over production of the hormone. Decreasing progesterone levels are responsible for triggering menstruation outside of pregnancy. It is possible that early pregnancy bleeding may be attributed to an insufficiently developed placenta.

Additionally, the study shows that the majority of women who experience early pregnancy bleeding do so around the time of their expected period, around 14 days after ovulation or cycle days 27-31.

Early pregnancy bleeding can cause mild cramping and bleeding, similar to what might be expected at the beginning of a period. However, so-called implantation bleeding is typically much lighter than normal menstruation, consisting of spotting lasting no more than three days.

Implantation bleeding can be distinguished from menstrual bleeding by:

  • Brevity and mildness. Implantation bleeding is limited to mild spotting which does not last more than three days.
  • Quality. Some women describe implantation bleeding as being brown or pink, as opposed to the red of their usual menstrual blood. Others, however, report that the blood is normal except in quantity.
  • Differences in accompanying cramps. Implantation cramps are typically milder than premenstrual cramps, and some women describe them as being different in quality. Implantation cramps may be entirely absent, or last for up to two days. Some women report a "sharp," "pulling," or "tingling" sensation that is unlike their usual premenstrual cramps.

Not all women experience early pregnancy bleeding.


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