3. Discussion
During the proliferation process, bacteria created endotoxin which is
harmful to embryonic development [7]. Washing is a commonly used
method to remove microorganisms from the embryo surface. However, it may
not be the most effective approach, as demonstrated by the patient in
our study who experienced failed pregnancies despite careful washing of
the embryos during the second and third transfers. This could be
attributed to the high bacterial load in the culture medium and the
qualitative nature of the washing procedure leading to recontamination
[4].
The zona pellucida is a critical structure that surrounds the oocyte and
later the developing embryo in humans. The ultrastructure of zona
pellucida has been clearly described in a related study [8]. It can
act as a protective barrier to prevent multiple sperm from fertilizing
the same oocyte. It also protects the developing embryo during its
journey through the fallopian tubes towards the uterus. However, in our
study, the zona pellucida can not protect embryo from bacteria. This can
be explained due to the porous structure of the zona pellucida makes it
challenging to completely eliminate microorganisms [5]. Indeed,
Familiari et al. performed a scanning electron microscopy (SEM) to prove
the spongy structure of zona pellucida of mature oocytes [9].
Additionally, during the clevage and blastocyst stage of embryo, the
outer surface of the zona pellucida also showed a spongy texture with
wide and flattened fenestrations. Therefore, we suggest that zona
pellucida removal is an optimal method to stop bacteria contamination.
This approach can be done sucessfully using both chemical (Tyrode acid)
and physical method (Laser). However, the effectiveness of Tyrode acid
can vary depending on the thickness the zona pellucida. Additionally,
there is a slight risk of exposing the embryo to Tyrode acid, which
could potentially affect its viability or development. In our study, by
utilizing a laser to remove the contaminated zona pellucida from the
embryos, the recontamination of bacteria was prevented, leading to a
successful live birth for the patient. Moreover, the removal of the
barrier between the embryo and the uterine environment potentially
enhanced implantation and increased the chances of a successful
pregnancy [10].
In this case, the use of laser for zona pellucida removal allowed for
precise and controlled manipulation. It also can be used in a wide range
of cases, including embryos with thick or tough zona pellucida. It is
worth noting that the successful outcome obtained in this patient after
repeated implantation failures, with a healthy live birth, suggests the
potential benefit of this technique. However, further studies with
larger sample sizes and controlled settings are needed to validate these
findings. Additionally, it is important to consider the risks and
limitations associated with zona pellucida removal. The procedure
requires skilled personnel and specialized equipment to ensure proper
execution and minimize the risk of damage to the embryo. There is a
possibility of damage to the embryo during the removal process,
potentially impacting its viability. Long-term follow-up studies are
necessary to evaluate the potential effects of zona pellucida removal on
fetal development and health.