The 27-year-old confirmed that she will miss the Commonwealth Games in Glasgow this summer, although she hopes to defend her Olympic heptathlon title in Rio in 2016.
She released a statement to reveal the news that she admitted was "very unexpected".
"I have some very unexpected but exciting news to share - Andy and I are expecting a baby," said Ennis-Hill.
"We are completely overwhelmed, with excitement and a degree of anxiety that I am sure all first time parents will relate to.
"My plans for 2014 have been completely turned upside down, but having had a couple of weeks to think about things from a career point of view I am 100 per cent set on returning to full time athletics once our baby is born and go for a second gold medal at the Rio Olympics in 2016 - that challenge really excites me.
"But in the short term I will make our baby a priority and enjoy the whole experience as much as possible.
"I am sorry I won't be in Glasgow for the Commonwealth Games, but know it will be an amazing occasion. I will be at home awaiting the arrival of a little Ennis-Hill."