Federal Finance Minister Penny Wong and her same-sex partner are having a baby.

The senator released a statement today revealing her long-term partner Sophie Allouache was expected to give birth in December after falling pregnant through IVF.

"Like any expecting parents, the prospect of welcoming this child into our lives fills us both with joy," Senator Wong said.

"We are extremely grateful to our IVF service and staff, and to our donor, for giving us the opportunity to raise a child together."

The couple know the biological father who will be known to the child.

But his name will not be released to the media, Senator Wong said.

"We have chosen to make this statement about Sophie's pregnancy as we understand there may be public interest due to my position.

"I do not propose to make any further statements following today," she said.

Treasurer Wayne Swan was the first of Senator Wong's colleagues to congratulate the couple.

"As any parent knows, starting a family is one of the most exciting times in your life, so this is just great news for Penny and Sophie," Mr Swan said in a brief statement.

"On behalf of my own family and all my staff, I wish them both all the best on the long but enormously rewarding road of parenthood."

Deputy Opposition Leader Julie Bishop passed on the congratulations of the Coalition.

"The birth of a child is a cause for great happiness for Penny Wong and her partner," she said.

"I wish them all the very best in the coming months."

New South Wales Christian Democrats leader Fred Nile claimed Senator Wong was setting a bad example by having a baby with her gay partner.

The Reverend Nile, who has previously stated his opposition to same-sex relationships, said he was totally against a baby being brought up by two mothers - adding the baby has human rights.

He said Senator Wong did not need to make the pregnancy public, saying the announcement just promoted their lesbian lifestyle and tried to make it natural when it was unnatural.