Exactly how Keli Lane managed to conceal five pregnancies in eight years.

In September 1996, Keli Lane arrived at a friend’s afternoon wedding alongside her boyfriend Duncan Gillies.

Just two days earlier, the then 21-year-old had given birth to a baby girl, Tegan Lee Lane.

Her friends and even Gillies himself didn’t suspect a thing – Keli was her normal self, dancing and drinking the night away.

But to this day, Keli’s daughter Tegan has never been found.

Now, eight years on from being convicted of murdering her two-day-old daughter, Keli is determined to prove her innocence.

The 43-year-old reached out to award-winning Australian journalist Caro Meldrum-Hanna to investigate her story.

In new ABC series EXPOSED: The Case of Keli Lane, Caro and investigative journalist Elise Worthington delved into one of Australia’s most notorious crimes, investigating what exactly happened to Tegan, who would now be 22 years old.

The first episode of EXPOSED: The Case of Keli Lane will air on Tuesday September 25 on the ABC.

But perhaps the most baffling part of the Keli Lane case is how she effortlessly managed to conceal five pregnancies from her parents, her water polo team mates, her boyfriends and her family.

Between 1992 and 1999, Keli fell pregnant five times. But over the course of those eight years, there was only one person who ever knew about her pregnancies.

When she fell pregnant for the first time in 1992 at 17 years old, Keli told her high school boyfriend before terminating the pregnancy.

She later fell pregnant again at 18 years old in 1994, before terminating the pregnancy at 20 weeks.

“From Keli Lane’s point of view, she thought [concealing the pregnancies] wasn’t hard at all. It was actually sort of remarkably easy,” Caro told Mamamia.

“She was wearing baggy clothes, and from all accounts, she did carry her pregnancy differently than most of us visualise a pregnant body,” she added.

“She carried around the stomach, rather than the classic sort of egg shape.”

After the two pregnancy terminations, Keli went on to carry and deliver three babies.

In 1995, she gave birth to a baby girl who was soon adopted out.

Her second daughter, Tegan, was born a year later on September 12 1996 at Western Sydney's Auburn Hospital.

Three years later in 1999, Keli gave birth to a son who was also adopted out.

Even right up until she was at full-term pregnancy, no one discovered that Keli was pregnant. She even continued to play elite water polo right into the end of the third trimester.

"She was on another level with functioning of her body," Caro explained. "[As an elite athlete] she learned how to isolate and compartmentalise pain. To put the pain in a box and push through it."

"When something was making her feel uncomfortable or she would be feeling pain, she was trained to ignore [that pain] and keep going."

In recordings shared by the ABC this morning of a phone call between Keli and Caro, Keli shared how she became good at isolating herself while concealing the pregnancies.

"I don't know how no one ever said anything to me," she said in one of the recordings.

"Concealed pregnancies do happen," Caro told Mamamia. "They happen in all levels of society... It’s a very, very real phenomenon. And when they do happen, it says more about the society or community that girl was growing up in than it does about the girl. There are fears, shame, conservative values, ambitions, life goals, you name it – it all plays a part.”

In Keli's case, there were a number of factors that drove her to conceal her pregnancy from the fear of disappointing her parents to the fear of being shamed in the community.

“There was that fear of disappointing her parents and shattering that image," Caro said.

“There was was no room, it seemed, for mistake. You were a winner, Keli Lane was a winner, and that was her role in the family."

EXPOSED: The Case of Keli Lane will air on three Tuesday nights, beginning at 8:30pm on Tuesday September 25 on ABC and iview.