"We studied a large number of surplus embryos and the differences in growth between male and female embryos were significant", he said
Dr. Dumoulin and his team looked at the sex and numbers of cells in 330 blastocysts collected from conventional IVF cycles and 322 blastocysts collected from ICSI cycles during a 5 year period. The embryos had been left over after transfer and were unsuitable for freezing. They found that both female and male embryos originating from IVF had a similar mean number of cells (50.8 in female and 46.2 in males), there were significant differences in those originating from ICSI (39.8 in females and 55.3 in males).
"ICSI had already been shown to have an adverse effect on embryo development", said Dr. Dumoulin, "and it was known from animal studies that external stress factors affect embryos of different sexes differently. Our work has shown clearly that ICSI is a significant factor in influencing growth rate, although we do not yet understand why."
The next step, said Dr. Dumoulin, would be to measure whether the embryo growth differences were restricted to the pre-implantation period or whether they were present (and measurable) at a later stage in development. "If these differences were to be perpetuated at a later stage it would clearly be significant for clinical practice," he said.
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