Iliana Ilieva with her eight-week-old son,Victor, who is an IVF baby.

Iliana Ilieva with her eight-week-old son,Victor, who is an IVF baby. Photo: Dallas Kilponen

After six agonising years of fertility treatment, Iliana Ilieva named her son after her "personal victory" of becoming pregnant. But to researchers, eight-week-old Victor Valeri is among an alarming surge in the number of boys being born using in vitro fertilisation techniques.

AFTER six agonising years of fertility treatment, Iliana Ilieva named her son after her "personal victory" of becoming pregnant. But to researchers, eight-week-old Victor Valeri is among an alarming surge in the number of boys being born using in vitro fertilisation techniques.

IVF, which has boomed in Australia in the past 10 years, is skewing gender rates so much that scientists have issued a plea to clinicians to warn parents of the potential outcome.

About 300,000 babies are born in Australia each year - with nature producing slightly more boys than girls (51.5 per cent). But for women having standard IVF, where the embryo is incubated for five days, that probability rises to 56.1 per cent.

Patients undergoing intracytoplasmic sperm insemination (ICSI), where one sperm is selected and injected into an egg, are significantly more likely to have girls, while freshly created embryos, as opposed to those frozen and thawed, are more likely to be male.

In research published today in the British Journal of Obstetrics and Gynaecology, experts from the University of NSW analysed 13,368 births from fertility clinics in Australia and New Zealand but were still unclear as to how the procedures skewed gender, said the lead researcher, Jishan Dean.

One possibility was that more male embryos were chosen for transfer because their cells multiplied more quickly, she said. Other studies suggested that male embryos coped better in the cultures and incubators used to grow them.

About 10,900 IVF babies are now born each year - twice as many as in 2004 - making a gender imbalance a serious issue for social researchers, but it was unlikely to concern parents, Ms Dean said.

"The reality is that most people having IVF just want a baby - boy or girl," she said.

Michael Chapman, the director of IVF Australia and an author of the study, agreed, saying that only 3.5 per cent of babies were born using assisted reproduction and any gender changes would not have a huge social impact.

But the journal's editor-in-chief, Philip Steer, argued that imbalances in India and China had led to "significant problems, with some men being unable to find a wife".

"It is important that we don't allow such imbalances to occur unintentionally, simply because we have neglected to study the factors that influence [sex ratio]."

For Ms Ilieva, 37, from Sylvania Waters, gender was never an issue.

She has an 11-year-old daughter but endured the death of her first baby, three ectopic pregnancies and three IVF cycles before becoming pregnant with Victor.

"We really didn't care. We just wanted a baby."