[2] In the first place, as compared to spermatozoa, round spermatids do not possess easily perceptible morphological characteristics and are immotile.

[2] The microinjection procedure for ROSI also differs slightly from that of ICSI, since additional stimuli are needed to ensure proper oocyte activation after spermatid injection.

[3] The clinical potential of ROSI in the treatment of male infertility due to the total absence of spermatozoa has been corroborated recently by a publication reporting on the postnatal development of 90 babies born in Japan and 17 in Spain.

[6] Even with severe teratozoospermia, microscopy can still detect the few sperm cells that have a "normal" morphology, allowing for optimal success rate.

One of the main advantages of this method is spermatozoa quality, as the selected ones have better motility, morphology, little DNA fragmentation and less quantity of reactive oxygen species (ROS).

[7] Another way to perform the selection is the MACS technique, which consists of tiny magnetic particles linked to an antibody (annexin V) which is able to identify more viable spermatozoa.

[11] The technique was developed by Gianpiero Palermo at the Vrije Universiteit Brussel, in the Center for Reproductive Medicine headed by Paul Devroey and Andre Van Steirteghem.

[17] Sharpe et al comment on the success of ICSI since 1992 saying, "[t]hus, the woman carries the treatment burden for male infertility, a fairly unique scenario in medical practice.

Depending on the total amount of spermatozoa in the semen sample, either low or high, it can be just washed or capacitated via swim-up or gradients, respectively.

[22] A recent clinical trial showed a sharp reduction in miscarriage with embryos derived from PICSI sperm selection.

[24][25] Ultra-high magnification sperm injection (IMSI) has no evidence of increased live birth or miscarriage rates compared to standard ICSI.

[26] A new variation of the standard ICSI-procedure called Piezo-ICSI uses small axial mechanical pulses (Piezo-pulses) to lower stress to the cytoskeleton during zona pellucida and oolemma breakage.

[27] The procedure includes specialized Piezo actuators, microcapillaries, and filling medium to transfer mechanical pulses to the cell membranes.

The procedure involves creating a hole in the zona to improve the chances of normal implantation of the embryo in the uterus.

It is uncertain whether ICSI improves live birth rates or reduces the risk of miscarriage compared with ultra‐high magnification (IMSI) sperm selection.

[32] For example, it was shown that after ICSI the follicular fluid of unfertilized oocytes contains high levels of cytotoxicity and oxidative stress markers, as Cu,Zn-superoxide dismutase, catalase, and lipoperoxidation product 4-hydroxynonenal (4-HNE) -protein conjugates.

[33] There is some suggestion that birth defects are increased with the use of IVF in general, and ICSI specifically, though different studies show contradictory results.

In a summary position paper, the Practice Committee of the American Society of Reproductive Medicine has said it considers ICSI safe and effective therapy for male factor infertility, but may carry an increased risk for the transmission of selected genetic abnormalities to offspring, either through the procedure itself or through the increased inherent risk of such abnormalities in parents undergoing the procedure.

[36] In vanishing twin pregnancies with a second gestational sac with a dead fetus, first trimester screening should be based solely on the maternal age and the nuchal translucency scan as biomarkers are significantly altered in these cases.