Mum of 'world's oldest baby' speaks out and people can't get over words used to describe him

The mother of a child nicknamed the 'world's oldest baby' has inadvertently caused quite the commotion online.

For those out of the loop with the record-breaking story, Thaddeus Daniel Pierce was born in the US to parents Lindsey, 35, and Tim Pierce, 34, on Saturday (July 26).

Of course, the birth of any child is a momentous occasion, and aside from an announcement in a newspaper or a post on social media nowadays, most births would not typically spark such global interest unless it was something truly special.

However, even before their son's arrival, the Ohio couple knew they were embarking on something out of the ordinary.

Why? Because despite the Pierces themselves being in their mid-30s, Thaddeus already had a 30-year-old sister.

Still confused? Don't worry, we were for a while, too!

Lindsay and Tim Pierce welcomed their son last week (Lindsey and Tim Pierce/Rejoice Fertility Clinic)

To put it simply, Thaddeus is the result of an embryo that was frozen over three decades ago. The cells had come from Linda Archerd, now 62, and her then-husband, whom she has since divorced, and were frozen through IVF in 1994.

After the pair had a daughter, born that year through the fertility process, Linda decided to freeze her other embryos. She later donated them to an agency for similarly struggling couples, such as the Pierces.

As such, Thaddeus has broken the record for the longest-frozen embryo to result in a successful birth.

In the days following his headline-hitting arrival, the Pierces have described their experience as being 'like something from a sci-fi movie'.

Speaking to MIT Technology Review over the weekend about both her newborn son's arrival, Lindsay recalled: "We had a rough birth but we are both doing well now," adding: "We are in awe that we have this precious baby."

She also went on to admit: "We didn’t go into it thinking we would break any records. We just wanted to have a baby."

The mum also described her son's demeanour, telling the outlet that 'he is so chill', which left readers unsure whether she intended it to come across as a freezer pun or not.

Thaddeus was born via IVF (Getty Stock Image)

Either way, the remark has gone viral online, with one social media user writing: "'He is so chill' made me chuckle. Welcome to the world, baby!"

Another commented: "Dudes been frozen for decades. He’s chill by default," while a third jibed: "'He is so chill' after being frozen for 30 years geeks."

Someone else went on to joke: "Saying yo baby is so chill when it’s been frozen for thirty years is wild work."

Thaddeus' biological mother, Linda, has even been sent some photos of Thaddeus, and has admitted she can’t wait to meet him.

"The first thing that I noticed when Lindsey sent me his pictures is how much he looks like my daughter when she was a baby," she said. "I pulled out my baby book and compared them side by side, and there is no doubt that they are siblings."