A twin born three times the size of her sister still topples over her at double her weight and their mum says strangers "can’t believe they are twins"."

Tiny Reagan, now 19 months old, was born 11 weeks early and weighing just 1lb, and was dwarfed by her twin Mila, who was 2lbs 13oz.

Mum Audrieanna Lambert, 33, said it was a miracle Reagan was alive at all after medics' stark warnings she wouldn't survive the pregnancy – when she stopped growing at 20 weeks.

The twins were born via a c-section in December 2021 and Mila spent 45 days in West Penn Hospital, Pittsburgh, Pennsylvania, US, before she could come home.

Reagan spent 118 days in hospital, battling sepsis, before she could join her sister at home in Washington, Pennsylvania, US.

Now the twins are both thriving but are still different sizes, with Mila now weighing 20lbs 8oz and Reagan 13lbs 7oz.

Tiny Reagan wears three-month-old clothes whilst Mila is in 12-18 months.

Despite it all, they are both walking and talking, and Audrieanna said strangers "can’t believe they are twins"."

Audrieanna, a claims specialist, said: "Mila towers over Reagan."

"They are both excellent."

"Despite her size, Reagan is walking and exceeds expectations."

"I still get questions – people say ‘wait, are they twins?’"

"They ask how close they are in age and are shocked when they find out they are twins."

"People are stunned to see Reagan walking – as she looks too small for a baby who can walk."

Audrieanna and husband, Chase, 30, a union labourer, found out they were expecting in June 2021 after their first round of IVF, following years of pregnancy struggles.

At six weeks, the couple discovered they were expecting twins but were told that Baby B - Reagan - was measuring small and it was possible they would lose her early on during the pregnancy.

At 15 weeks, they were told Reagan had caught up but at their 20-week scan she was falling behind again and 18 per cent smaller than her sister.

Audrieanna said: "The doctors were not sure if she would make it at that point."

At 24 weeks, the couple were given the devastating news that Reagan was now 50 per cent smaller and suffering issues with her cord flow - the transfer or nutrients from the mother's blood across the placenta to the foetus through the umbilical cord.

Audrieanna was told the tot would pass away within two weeks.

She said: "They were certain she wouldn’t make it because everything they knew medically told them she wouldn’t."

"I was devastated."

But two weeks later, at the 26-week scan, doctors found that Reagan's heart was still beating, and Audrieanna was admitted to West Penn Hospital at 27 weeks to be monitored.

She made it to 29 weeks before Regan's cord flow changed, and the babies had to be delivered by emergency c-section.

The twins were born on December 10, 2021, at 16.32pm, with Mila weighing 2lbs 13oz and Reagan 1lb at 16.33pm.

Both twins had to be taken straight to the NICU.

She said: "When I saw Reagan, she was so small she could fit in your hand."

"I knew she was going to be tiny, but she was still so much smaller than I had imagined."

"Mila was three times the size."

"But Reagan was fully developed despite how minuscule she was."

''We were finally allowed to hold them when they were five days old.

"It was magical, but they were so delicate and tiny."

Reagan battled sepsis and was transferred to UPMC Children’s Hospital of Pittsburgh.

Mila recovered well and was strong enough to go home in January 2022, after 45 days in hospital.

"It was so lovely to have Mila home but so hard to have to keep travelling back and forth to see her sister and for them not to be together," Audrieanna said."

Reagan spent another three months in hospital, receiving blood transfusions to help her grow so she could finally come home in April 2022.

Now 19 months old, the twins are hitting their milestones.

Reagan is walking and can say 15 words, while Mila is running and has a vocabulary of 60 words.

Audrieanna said: "She’s pretty awesome."

"Her walking isn’t perfect but she’s very independent."

"Mila runs everywhere."

"She’s Reagan’s biggest cheerleader."

"If Reagan does something new, Mila’s face lights up."

The twins shock strangers at their size difference but Audrieanna is delighted the pair will be able to go to nursery and school together.

She is expecting a third girl in October 2023 with Chase.

She said: "They kiss my belly."

"The newborn will probably be in the same clothes as Reagan and will outgrow her."

"We’re so excited."