Mrs Herald, who is just 2ft 4ins, was told that becoming pregnant could kill her but has already defied doctors to have two healthy babies.
The 35-year-old from Dry Ridge, Kentucky, USA, suffers from Osteogenesis Imperfecta, which causes brittle bones and underdeveloped lungs, and means she failed to grow.
Now Mrs Herald, who uses a wheelchair, and her husband Will, who is 5ft 9ins, are awaiting the birth of their third child, due in the next four weeks.
She cannot hold her daughter because her belly gets in the way, and has to rely on her husband Will to do most things around the house.
Mrs Herald admits being pregnant is "uncomfortable" and leaves her bedridden for weeks on end. By the time the new addition, a boy, is one he will already tower over his mum.
But despite all the obstacles, Mrs Herald and her husband, a trainee priest, say they want even more children.
The couple met in 2000 while working for a supermarket in their home town and were desperate for a family after marrying in 2004.
But doctors warned Mrs Herald a baby would grow so large inside her tiny body it would eventually crush her organs.
"It broke my heart that I couldn't have kids," she said.
"All my life my parents had told me that I could do anything. Then there were these doctors telling me that we couldn't be a complete family. It really hurt."
Eight months later, the couple were thrilled when they discovered Mrs Herald was pregnant and decided to go ahead even though family and doctors begged them to reconsider.
"They all told me that I would die. They begged me not to have a baby. Even my mother said,' You know you won't survive right?'
"I told her: 'It's a miracle that I am here, that I have life, why couldn't this be a miracle too?'"
After 28 weeks, doctors performed a cesarean section and daughter Kateri was born, weighing just 2lbs and 1oz in 2006.
She grew well but there was heartbreak for the family when they discovered Kateri had inherited Mrs Herald's condition and would also never grow to a normal height.
But the young family resumed life as normal, before Mrs Herald became pregnant a year later.
"It was kind of like the last time, everyone screamed: 'What are you doing?' at us," she said.
"The doctors told me I was pushing my luck. But we just prayed that God would bring us through it."
She admits that the second pregnancy has taken its toll, saying: "It was hard, I got so much bigger faster. At my worst point I remember bursting into tears, because I looked like a beach ball with a head and little feet.
Doctors tried to let the second baby stay in Mrs Herald's body for as long as possible, letting her pregnancy go to 34 weeks before taking her into theatre.
Daughter Makaya who, at 18 inches was more than half her mum's body length when she was born, weighed 4lbs and 7oz.
Now both girls are bigger than their mother, who is now 30 weeks pregnant with her first boy.
She said: "It's getting tougher and tougher to move.
"At the moment because I'm getting really big again I can't hold my youngest daughter because my belly gets in the way and I can't get my arms around her."
Mrs Herald added: "All my babies are miracles, but we haven't thought about if we're going to have some more, as they're a real handful right now.
"We didn't plan to have more than two kids, we just think that they're a great gift to the world, and when I look at them I see Will and I feel so full of love, it's tough not to want more."
