Mrs Chalk, 31, who has undergone IVF treatment, made headlines by having quadruplets twice.

Now, she and her husband Darren, who live in Sydney, have added to their brood, and are now the proud parents of 11 children under the age of seven.

The first set of quads - two boys and two girls - were born in August 2004 and are due to start school next year.

Mrs Chalk became pregnant with her second set of quads in 2005. The babies were delivered in October of that year but only three survived.

The couple also have a six-year-old daughter and another girl born in 2007.

They are understood to have used a low-grade infertility treatment for the multiple births.

"We'd love to have more children, but medically, that's it," Mr Chalk told the Courier-Mail newspaper. "We'd have to buy a bigger bus!"