A phenomenon of “missing girls” could be afflicting Victoria, as a study of more than a million births suggests some parents could be aborting unborn female babies or undergoing embryo selection overseas in order to have a son.

If nature was left to take its course, it is expected that for every 100 girls born, about 105 boys will be brought into the world.

But in findings researchers say indicate “systematic discrimination against females starts in the womb”, mothers within some key migrant communities are recording sons at rates of 122 and 125 for every 100 daughters in later pregnancies.

Lead researcher Dr Kristina Edvardsson from Melbourne’s La Trobe University said it showed gender bias persisted in Victoria, despite laws banning people from choosing the sex of their child, other than for medical reasons.

“We believe that some women may be terminating pregnancies after discovering they are expecting a girl and in other cases are travelling overseas to access non-medical sex selection services through assisted reproduction,” she said.