An in vitro fertilization (IVF) procedure normally starts with hormonal stimulation, proceeds with oocyte recovery trough an ovarian puncture, oocyte fertilization, culturing of the resulting embryos and concludes with an embryo transfer procedure. The step considered by many to be the most technically complicated is the oocyte fertilization step. This is especially true if fertilization is carried out by the IntraCytoplasmic Sperm Injection (ICSI) method. The other main method of fertilization is called Conventional In Vitro Fertilization.
What is ICSI fertilization?
ICSI fertilization is mainly used in male factor infertility cases. The nature of the procedure allows oocytes to be fertilized even in the presence of only single motile spermatozoa with good morphology. This is achieved as the embryologist catches these single spermatozoa by means of the so called micromanipulator (See Fig.). Each of the selected spermatozoa is separately immobilized, aspirated in the injection micropipette and injected into a single oocyte.
IMSI is an improved version of ICSI (IntraCytoplasmic Sperm Injection) which allows the embryologist to look at spermatozoa at a much higher magnification (x 6000), compared to x600 or less for the standard ICSI procedure. The higher magnification allows much more detailed visualization of subcellular structures like the acrosome, the head, the midpiece, the cytoplasmic droplet or the tail of the spermatozoon. Therefore, with IMSI a much more precise selection of spermatozoa is achieved. Following the selection of particular spermatozoa, the IMSI procedure is identical to ICSI.
The IMSI method is useful for patients with a very low percentage of spermatozoa with normal morphology. Although it is more laborious and much more time-consuming, for those patients it is definitely beneficial. In some cases the IMSI procedure is also recommended for couples with a few unsuccessful ICSI cycles as well as couples with recurrent abortions. Talk to your reproductive specialist to find out which is the most suitable method in your case!