Melbourne mother expecting quins!:

In what could almost be deemed a miracle, the woman conceived the five babies without the help of IVF, the Seven Network reported.

The chances of conceiving quintuplets naturally is about one in 55 million, doctors say.

Obstetrician Dr Len Kilman said conceiving a multiple pregnancy naturally over the age of 45 was rare.

"Fertility naturally declines and to conceive spontaneously after the age of 45 is particularly uncommon and to have a multiple pregnancy after the age of 45 is particularly uncommon," Dr Kilman told the Seven Network.

It will be the first set of quintuplets born in Victoria in three decades.

The mother, who does not want to be identified, is in her 29th week of pregnancy and is expected to give birth at the Monash Medical Centre.

The last quintuplets born in Victoria were the Kissane quintuplets in February 1980.

None of the quins, four boys and a girl, who were born 11 weeks premature, survived.

In 2011, a Brisbane lesbian couple gave birth to quintuplets conceived with the help of a sperm donor.

Rosemary Nolan and Melissa Keevers gave birth to Noah, Charlie, Eireann, Evie and Abby.

The babies were born more than 13 weeks' premature and each weighed less than a kilogram.

It is believed there are about a dozen sets of quintuplets in Australia.

A Monash Medical Centre spokeswoman would not confirm the Seven Network report, saying only they had a patient who was expecting a multiple birth.