Parents are increasingly asking to choose the sex of their children in an attempt to lower their baby's risk of diseases and disorders ranging from cancer to autism, IVF doctors say.
Figures from one of Sydney's top IVF clinics show about one in 20 parents seeking embryo screening are looking to have a female baby to reduce their risk of autism.
Fertility experts say the issue is the tip of the iceberg with a huge range of tests becoming available. Some clinics in the US now offer testing for up to 600 different genetic markers.
The medical director of the fertility company Genea, Mark Bowman, said his organisation had done more than 100 cycles of what is known as "pre-implantation genetic diagnosis" this year, mostly for conditions such as cystic fibrosis, where family members have the condition and a gene mutation is known to be responsible.
"In a way these tests are the ultimate preventative medicine," Associate Professor Bowman said.
National Health and Medical Research Council guidelines say sex selection is not allowed, except to prevent the transmission of a "serious genetic condition", although some Australian couples travel overseas to have the procedure for ''family balancing''.
He said in about one in 20 cases parents sought pre-implantation diagnosis simply for sex selection to lower their risk of having a child with autism, after having an autistic child. Boys are about four times as likely as girls to have autism, but there is no genetic test for it.
Some also sought sex selection for conditions where the boundaries between genetic and social causes are mired in controversy, such as depression and attention-deficit hyperactivity disorder.
University of Sydney senior lecturer in bioethics Chris Jordens said autism had a strong genetic basis, so it was within the guidelines. He said sex selection may benefit children with autism, if their parents were able to have a second child that did not have similar high-care needs. But what constituted a "genetic condition" could be blurry.
"There is no kind of perfect line between a genetic condition and a non-genetic condition," he said. "All diseases that result from environmental factors have genetic components."
Another senior lecturer in bioethics, Ainsley Newson, said pre-implantation genetic diagnosis was not undertaken lightly.
"It's not a frivolous decision: it is expensive, has a low success rate and is not covered by Medicare," she said. "However, these latest requests are interesting because in this case it cannot guarantee that the child will not develop autism - it will only lower the risk."
Professor Bowman said other frontiers in IVF testing included "whole chromosome" testing for random abnormalities that can cause miscarriage. Yet all tests carried potential risks to the embryo.
"The question is, what is the best thing for that woman: continuing to try on her own and miscarrying versus doing IVF and testing the embryos? We can't know for sure that everybody definitely benefits."
Fertility Society of Australia vice president Michael Chapman said the new frontiers posed a "huge challenge".
At a recent conference in Chicago, he saw a number of United States IVF providers offering parents without the conditions tests for between 180 and 600 common gene mutations, such as the BRCA ''breast cancer'' genes.
"No one in Australia is offering this kind of thing yet, but it's definitely coming, because the demand is there," he said.
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