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A single sperm is sucked up into a microscopic thin, sharp tube and injected
directly into a woman's egg. This procedure, introduced in 1992, allows couples
with extremely small numbers of low quality sperm to attempt pregnancy. Both
the egg and the sperm are specially prepared for this procedure. Fine
variations in the technique are required to optimize pregnancy rates.
This genetic diagnosis procedure tests cells of the embryo for abnormalities.
The ripening egg produces two small cells called polar bodies which play no
part in fertilization and development; in fact, they degenerate immediately
after fertilization. However, the chromosomes can still be seen in these cells
up to six hours after recovery of the eggs, so it is possible to determine the
chromosomal makeup of the egg.
The polar body is removed by making a gap in the outside shell (or zona
pellucida) of the egg, and one or both polar bodies are removed by gentle
aspiration. The biopsied polar bodies are analyzed for abnormalities. The egg
is returned to the incubator, and later, fertilized. The results are available
before embryo replacement.