In our clinic, a research team led by Dr. Zuzana Holubcová performed a clinical study examining the correlation between the presence of the spindle apparatus and the success rate of post-fertilization development after ICSI. This study confirmed that the chance of successful embryonic development of fully mature eggs displaying a spindle is more than three times higher in comparison with eggs that are fertilized prematurely. The benefit of this approach is evidenced by healthy-born babies conceived from late-maturing eggs which were at risk of premature fertilization.
To be successfully fertilized an egg has to be mature. During in vitro fertilization, the maturity of the egg is usually evaluated by an embryologist using a light microscope. The embryologist checks whether the egg already expelled a small adjoint cell, known as the polar body.
However, the mere presence of the polar body doesn’t necessarily mean that the egg has already completed its development. The true sign of egg maturity is the presence of the spindle apparatus that divides the genetic material after fertilization. Thus, to an embryologist, the egg may sometimes seem mature at first sight, but after the sperm injection, it will not develop successfully because fertilization was performed prematurely.
Left: the egg in transmitted light, the arrow showing the polar body. Right: the same egg with the chromosomes (blue) and meiotic spindle apparatus (pink) visualized.
Polarized light microscopy enables spindle imaging of live human eggs.1,2 This method enables the non-invasive assessment of the egg’s maturity before fertilization and optimization of ICSI timing
(Holubcová et al, JARG 2019 - adapted)
Who is eligible for polarized light microscopy?
Patients with whom we received an unexpectedly low number of mature eggs as a reaction to treatment, or who previously experienced unexplained fertilization failure might be recommended to have the maturity of their eggs examined by polarized light microscopy.
And how is the examination performed?
If polarized light microscopy reveals that the egg is not yet fully mature, the embryologist will postpone ICSI and keep the egg in culture for an additional few hours. Thus, the chance that the egg completes its development before fertilization
1 Keefe D, Liu L. Wang W, Silva C (2003) Imaging meiotic spindles by polarization light microscopy: principles and application to IVF. Reprod Biomed Online, Jul-Aug;7(1):24-9.
2 Kilani S, Chapman MG (2011) The use of polarized light microscopy in IVF. Expert Rev. Obstet. Gynecol. 6(3):241-246.
3 Holubcová z, Kyjovská D, Martonová M, Páralová D, Klenková T, Otevřel P, Štěpánová R, Kloudová S, Hampl A (2019) J Assist Reprod Genet. 2019 Mar;36(3):445-452.