A maid of honour didn't want to upstage the bride. So she hid her labour throughout the wedding ceremony.

If there was ever a time you don’t want to upstage your best friend, it’s during her wedding.

That’s what Karla Barry thought when she realised she had gone into labour just moments before walking down the aisle on her best friend Katie Letton’s big day.

But Karla didn’t let the impending arrival of her baby disrupt the day: she kept her labour a secret throughout the whole ceremony and photography session.

“I just didn’t want to ruin Katie’s day, so we didn’t tell her,” Karla told the West Australian.

Karla’s biggest concern was that her waters would break while she was walking down the aisle.

"I was worried about my waters breaking as I walked...I felt a sigh of relief when I got to the end," Karla told Mamamia.

Karla was monitored throughout the day by the bride's mum, who is an experienced midwife.

When her true contractions started just before the speeches, the maid of honour and her fiancé, Adam Hitchcock, left the wedding to head for the hospital.

"My partner went up to Katie after the first dance and said, 'We have to go, Karla has been in labour all day!' She was like, 'What? Why didn't you tell me?'" Karla told Mamamia.

"I cried as I still didn't want to leave [the wedding], even though my contractions were three minutes apart. As I was leaving, Katie gave me a massive hug and wished me luck - it was a pretty emotional moment."

Karla was worried the hospital would send her home and she would have "missed the end of [Katie's] special day for nothing", but the couple welcomed baby Xavier 2am the next morning.

Xavier wasn't due for another week, but in a stroke of good fortune, Karla's fiancé had packed her hospital bag the morning of the wedding.

"[Adam] picked that [Xavier] was going to arrive on the wedding day early on in my pregnancy, but I never really believed him because they often say most first babies are born late," Karla said.

"Before we left in the morning of to the wedding my fiancé said, 'I'm just going to pack the hospital bags in case!'".

The new family is doing well, with Karla describing Xavier as a "dream baby".

"He is the most content baby we could have asked for. We are very, very lucky," she said.