Intracytoplasmic Morphologically Selected Sperm Injection (IMSI) is a sperm injection (ICSI) of a specially selected single sperm directly into the mature egg. IMSI is a new and relatively unstudied technique. Sperm often have have abnormally shaped heads and often have vacuoles (cavities) and it is believed that these abnormal sperm are less likely to carry normal genetic material. IMSI use high power magnification to identify these abnormalities of sperm, therefore select the most normal looking sperm. Because sperm are so tiny compared to the egg, special high power magnification is required.
Who is IMSI for?
This is a treatment option if the male has
- poor sperm motility
- poor sperm morphology
- a low sperm count
- surgically recovered sperm.
What are the steps involved in the IMSI procedure?
A fresh or frozen semen sample is prepared on the day of the procedure by an embryologist
Under a microscope, an embryologist specially trained in the IMSI and ICSI technique, selects a single sperm for injection.
As with routine ICSI after the egg collection, the eggs are washed and examined to determine which eggs are mature enough for injection.
Using a fine glass needle the sperm is aspirated and then injected into the selected egg.
The injected eggs are cultured in labelled sterile culture dishes in an incubator overnight.
What are the risks of IMSI?
It is not known if there are risks of IMSI over and above those known from ICSI.
What are the risks of ICSI?
The first live birth following ICSI was reported in 1992 and therefore it is a relatively new technology.
The procedure is associated with irreparable damage to the eggs in approximately 5%‐ 10% of eggs injected and these eggs do not fertilise.
Children resulting from the ICSI procedure have an increased risk of a sex chromosomal abnormality of 1:100 compared to a risk of 1:400 of children who are spontaneously conceived. The manifestations of sex chromosomal abnormalities are variable but may include infertility and reduced intelligence.
Some but not all studies have shown higher birth defects in ICSI children particularly genital abnormalities. Up to 6% of ICSI children may have a defect at birth compared to 3% in naturally conceived children. It is not certain if these abnormalities are genetically determined as fathers with these conditions are more likely to need ICSI or whether the procedure of ICSI contributes to the birth defects. 93% of children born after ICSI are healthy at birth.
ICSI is a more expensive procedure than IVF and should only be performed instead of IVF when necessary. However very many children are conceived using ICSI in Australia and around the world.