A US woman has given birth to a whopping 6.7 kilogram baby boy.

Ali James Medlock was born on December 12 in Texas, weighing in at 6.7 kilograms (14 pounds and 13 ounces) breaking Arlington Memorial Hospital records.

"We did not expect 14 pounds," mother Jennifer told local media. "Nobody did."

Measuring 54.6 centimetres, Ali was the biggest baby the doctor who delivered him has seen in his 30-plus-year career, USA Today reports.

Due to his size, he had to stay in the neonatal intensive care unit for a week as he had low blood sugar and platelets levels. Ali's parents Jennifer and Eric thought their firstborn, Annabelle, was a big baby when she was born two years prior.

Annabelle weighed in at a still massive 4.4 kilograms - but little did they know Ali would be bigger.

Ali's condition improved for Christmas, and him and his mum are doing well, USA Today reports.

Newshub.