Australia may be affected by "missing girls," as studies of more than 1 million births suggest that some parents go overseas to have a child and have a female foetus or embryo choice.
If natural, then every 100 girls born, 105 boys born in the world.
But researchers say that "systematic female discrimination begins with motherhood," with mothers of certain key immigrant communities recording a ratio of 122 to 125 men to 100 women in late pregnancy.
Kristina Edvardsson, a lead researcher at La Trobe University, said this showed that although the law forbids the choice of a child's sex, there is still gender bias in Australia, unless there are medical reasons.
"We believe that some women may terminate pregnancy after the discovery of a female fetus, and others go overseas for gender selection," she said.
The study looked at 1.2 million births in Victoria between 1999 and 2015, with an overall male-to-female ratio of nearly 105 to 100, with some notable exceptions.
In 2011-2015, the proportion of Chinese-born mothers having boys and girls was 108 per 100. If they already have two or more children, the boys have a higher birth rate of 125 per 100.
Similarly, the ratio of men to women in the first child for mothers from India is 104 per 100, but after giving birth to two children, the birth rate of boys has soared to nearly 122 per 100.
Mothers from Southeast Asian countries also had a higher-than-expected birth rate for boys.
Gurdip Aurora, president of the Australian-Indian state of GP, in Melbourne, said he had recently encountered a gender selection involving an Indian immigrant husband and wife.
The couple had three daughters and the woman was pregnant again.
Dr. Aurora said: "they want to do B-mode ultrasound and then decide whether to have the baby or not. If it's a girl, don't. "
The GP refused to help them. Six months later, he said, he saw the mother again and the baby had disappeared.
"I asked her, and she said they had miscarried when they were on holiday in India," Dr. Aurora said. "I'm pretty sure it was a girl. They fell her."
B-mode ultrasound shows that both men and women are very popular in the world, and there is a new blood test that allows Australian parents to know gender within 10 weeks of gestation.
Dr Aurora blamed India's son-preference system on India's illegal dowry system, where married families were often forced to hand over large sums of cash, goods and property.
India's government estimates that 2 million girls are missing from their population every year because of sex-selective abortions and other forms of discrimination leading to premature deaths.
But not all immigrants do, says Dr. Aurora, who believes gender selection is not a major problem for Australian-born Indians.
Dr. Edvardsson said that after some immigrants arrived in Australia, they had smaller families, which meant that they were more likely to have a gender-selective next-born son because it was not feasible to have a son until they were born.
In Australia, sex selection through IVF is prohibited unless sex can help avoid some genetic abnormalities or diseases.
However, Australian parents go overseas to choose gender through IVF, and abortion agencies do not know that women who want to have an abortion want to have a son.
A strong desire to have a child of one sex is not necessarily specific to a particular race, and many fertility services have called on the government to allow gender selection in Australia for the sake of family balance.
Dr. Jim Tsaltas, IVF's clinical director in Melbourne, said there was support for the use of this technology for parents who already have two or more children of the same sex.
The researchers will now launch a larger project to study gender selection during pregnancy and the reasons for it all over the country.
