While modern technology is very good at making embryos in the laboratory, we still cannot control the implantation process. We do not know which embryo will become a baby - and this can be very frustrating, for both patients and doctors.However, you need to remember that embryo implantation consists of a series of phases in which the embryo has to appose and attach itself to the maternal endometrium and invade into it.
The enigma of embryo implantation
- why doesn't every embryo become a baby?
While modern technology is very good
at making embryos in the laboratory, we still cannot control the implantation
process. We do not know which embryo will become a baby - and this can
be very frustrating, for both patients and doctors!
Many patients who do not get pregnant
after an embryo transfer start believing that their bodies are defective,
and that they have "rejected" the embryo. They feel that if they failed
to become pregnant even after the doctor transferred 3-4 good quality embryos,
that they are flawed. However, you need to remember that embryo implantation
is a very complex process, which consists of a series of phases in which
the embryo has to appose and attach itself to the maternal endometrium
and invade into it.
First, the embryo has to undergo
further development, till it reaches the blastocyst stage, when
it hatches from its shell, known as the zona.
The hatched blastocyst then needs
to implant in the endometrium. This occurs during the period of
time known as the implantation window.
Apposition, or orientation of the
embryo (which is at the blastocyst stage at this time) within the cavity
of the uterus, starts when the cavity has become minimal due to the suction
of endometrial fluid by pynopods (small protrusions found on the
surface membrane of the cells lining the uterus).
Adhesion of the blastocyst is a progressive
phenomenon that ties the embryo to the endometrium and is the primary event
initiating invasion. Many molecules, such as cytokines, growth factors
and cell adhesion proteins called integrins play an important role
in this complex process during which the blastocyst and maternal endometrium
must undergo an exquisite dialogue.
Invasion is a self-controlled proteolytic
process that allows the embryonic trophoblast to penetrate deep into the
maternal decidua and to invade the endometrial spiral arteries by producing
chemicals called proteinases. How implantation is regulated and brought
about remains an enigma, but we need to remember that the implantation
process is surprisingly inefficient in humans - Nature is not always very
competent! After IVF, it's only about 10%, which means that only 10% of
embryos implant successfully to become a baby. The responsibility for this
low efficiency has to be shared between the embryo the endometrium, as
well as a defective embryo-endometrium dialogue. We still cannot successfully
predict which patient will get pregnant after embryo transfer. We now know
that one of the major reasons for failure of the embryo to implant is a
genetically abnormal embryo. Basic research on implantation is of great
interest today, because embryonic implantation is the major limiting factor
in allowing pregnancy after ART, but we still need to learn a lot about
this "black hole" in our knowledge, before we can learn to control it !
Some clinics attribute failure of the embryos to implant to immunological
problems - and even offer "treatment" for this, but there is no proof to
support this theory.
Remember, embryo implantation is
a complex process, which you cannot influence by your diet or physical
activity, so there is no need for you to blame yourself if the embryos
do not implant.
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- The Indiaparenting Team