It's one of the oldest immigration tricks in the book: get pregnant, fly to another country, have your baby, and voila - you've got immigrant ties to said country.

It even happens in Canada.

According to the Toronto Sun, Ottawa has discovered a number of unscrupulous immigration consultants in Hong Kong, who are coaching wealthy Chinese mainlanders about how to keep their pregnancies hidden while entering Canada on student or visitor visas.

"Avoid any baby or maternity items in luggage, wear dark clothing going through customs to look slimmer, and arrive in Canada no later than in the seventh month of pregnancy are among the tips given," notes the article.

Once here, the women go into hiding until they are due to give birth and then go to a hospital to deliver the baby. And, because all babies born in Canada are considered citizens, they could return later in life as a student, for example, and sponsor their parents under family reunification.

Immigration minister Jason Kenney admits his department isn't sure how widespread the problem is but is considering citizenship law changes to prevent so-called anchor babies from automatically becoming citizens.

"We don't want people to get the idea that citizenship is a way to get a passport of convenience, that Canada is a country to be exploited," he told the Sun.

Toronto based immigration attorney Michael Niren says he doesn't think anchor babies are a "growing problem" and that changing the citizenship rules would be like "throwing the baby out with the bath water."

"Kenney is on a mission to clean up the immigration system from Refugee cases to Citizenship claims. Yes there are many broken aspects of our immigration system but I think he is going way to far here," Niren told Yahoo! Canada News.

"The solution is not to terminate this method for citizenship all together. Free societies like Canada have always granted citizenship to those born on their soil. This, in my view, should be a right not a privilege.

"[Instead of changing the law,] I think more careful screening of applicants to Canada should be conducted. In some cases, medicals are required which would reveal pregnancies. Sometimes the government gets ahead of itself and forgets that we are still a democracy."