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Definition of Implantation:

Implantation is when a fertilized egg, or blastocyst, has attached into the lining of the uterine wall. It marks the beginning of pregnancy. The medical community, including the FDA, the American College of Obstetricians and Gynecologists, and the National Institutes of Health are in agreement that a woman is not considered to be pregnant until implantation has occurred.

So, medically speaking, successful implantation equals the start of a pregnancy.

The Journey Towards Implantation:

It may be helpful to better understand implantation when you take a quick look at the journey to pregnancy...

  1. After you have sex, sperm will travel through the vagina, in past the cervix and up to the fallopian tubes. This is where a sperm will most likely join with an available egg.
  2. So, the next step is conception. This is when the sperm joins the egg and fertilization has taken place.
  3. About 7-14 days after you have had sex, implantation will occur -- the fertilized egg will attach itself to the lining of your uterus. About 1/3 of women will have some bleeding when implantation takes place.
  4. You are now considered to be pregnant!

When Does Implantation Take Place?

To answer this question, we need to take another look at how you become pregnant. In order to become pregnant, you need to be ovulating (when your egg is released).

If you have unprotected sex anytime from about 5 days before to 24 hours after the time that you ovulate, conception can take. Then, the process of becoming pregnant takes several days -- the fertilized egg (now called a blastocyst) has only just begun its long journey. 

Once the egg is fertilized, it now has to travel all the way up into the uterus for implantation to take place.

As the blastocyst makes this journey, it will continue to grow in size. At the same time, its cells will continue to divide and reproduce. The implantation of a fertilized egg is estimated to take place about 9 days (+/-) after ovulation. So, once conception has taken place, the blastocyst has to travel up into the uterus, and then implantation takes place once the blastocyst has found the spot in the uterine wall that it wants to attach to. It takes an estimated 7 to 14 days from the date that you had sex for all of this to happen, implantation has taken place, and you are now officially pregnant.

Let's Quickly Recap:

I know that this stuff can be confusing, but it is important to understand. So, to recap the path towards implantation and pregnancy...

  1. First, conception occurs (a sperm fertilizes the egg).
  2. Next, the blastocyst travels up into the uterus.
  3. Now, it's time for implantation -- the process where the fertilized egg has become attached (or implanted) into the uterine wall.
  4. Implantation is the first “step” that triggers your body to start producing the hCG, (also known as the pregnancy hormone).

    Pregnancy tests (both home tests and blood pregnancy tests ones) look for the presence of hCG to confirm a pregnancy. Implantation must occur to for this hormone to be produced. If implantation has not taken place, a pregnancy test cannot detect hCG and will give you a negative result. So, implantation has to occur before a pregnancy can be recognized with a pregnancy test.

    So Am I Considered Pregnant Now?

    It takes several days to establish a pregnancy. The establishment of your pregnancy is NOT completed UNTIL your fertilized egg has implanted in the lining of your uterus. The medical community considers you to be officially pregnant once the implantation of your fertilized egg has taken place. And, you can confirm that you are pregnant by using a pregnancy test:

    • If you get a positive result on a pregnancy test, then you know that implantation has taken place (since your body had started to produce the hCG hormone, and the test detected this hormone).
    • If you take a pregnancy test before implantation occurs, the test will tell you that you’re not pregnant (since the production of the hCG hormone has not started, this hormone will not be in your system, and the test will not detect it).

    So the Bottom Line: Implantation Defines the Beginning of a Pregnancy

    A fertilized egg must make its way into the uterus and find a nice, cozy spot to attach to. If implantation does not take place, the fertilized egg will leave your body, probably during your period. So conception does not automatically equal implantation or pregnancy.  

    And, if you really want to become technical (I know there are some techies out there)... A trophoblast (a type of tissue) actually develops from the fertilized egg and then surrounds it. This trophoblast helps to implant the egg to the inside of the uterus. It begins to push its way into the uterine lining. Next, the trophoblast actually pulls the egg inside of the uterine wall. This trophoblast will then occupy your blood vessels and direct your blood to the fertilized egg. At this point, you can officially say that implantation has taken place and a pregnancy has begun!

    Pronunciation of Implantation:

    /im·plan·ta·tion/ ; (im″plan-ta´shun)


    Jones RE, Lopez, KH. (2014). "Human Reproductive Biology, 4th Edition." London: Elsevier.

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