A pair of identical twins from Perth who share everything including a boyfriend have say they plan to experience pregnancy together because their bodies have to be the same.

Anna and Lucy DeCinque, 30, are so concerned about mirroring each other that they wear the same clothes and have reportedly spent almost a quarter of a million dollars on cosmetic procedures to look the same.

On last night's episode of the SBS program Insight , the sisters told host Jenny Brockie that their lifelong efforts to look exactly alike would not go on hold for pregnancy.

"If I got pregnant Lucy would definitely get pregnant straight way — because our bodies need to be the same," Anna said.

Anna and Lucy DeCinque.

"We would try to make that happen, definitely. We are not trying right now — we love children and kids love us, but it's not the time for us," the twins said, often finishing each other's sentences.

"We would have to be exactly the same — even if we went through IVF at the same time."

The twins said they go to great length to make sure they remain exactly the same, which includes eating identical meals of the same size and undertaking the same fitness regimes.

"If she walks a few metres, I need to walk a few metres because we have to burn the same calories," Lucy said.

The pair said they only share one collective identity and each feels as if she does not exist without her sister.