Doctors can help manage pain, add to bone density and even straighten limbs surgically with rods. But a pregnancy, especially with a normal-sized fetus, can have "disastrous consequences," according to Tinkle.
"You have someone that small with a two-foot trunk and you put a 20-inch full-term infant into her belly -- already the pelvis is putting pressure on the lungs," said Tinkle. "And it's not just the baby, it's all the fluid and increase in size compression upwards that means [the mother] is going to have problems breathing."
"We don't like to see someone with Type 3 get pregnant because of the risks," he said. "If the mom can't breathe, she's probably going to be OK, but you could have a baby with all kinds of birth defects like cerebral palsy."
Doctors like Tinkle issue "strong recommendations" against getting pregnant because of other risks like damage to the spine and paralysis.
"When you are sitting there is a lot of stress on the spine and we do see what looks like old-age osteoporosis with the spine collapsing down," he said. "It's a constant worry."
Herald said she suffered no physical problems, even though doctors had told her it was impossible to have children.
All three of the Herald babies were born premature, at 32 and 33 weeks.
"Makaya was 4 pounds, 7 ounces and she was double the size of both the other kids together," she said.
The couple relied on the book "Supernatural Childbirth" by Jackie Mize, a Christian guide for women who have been told they could never have children.
Raising three children, especially a 2-year-old who is taller, has not been easy, but she has help.
Wil Herald does the night feeding and she breast feeds Malachi during the day. Herald has a special platform to change diapers and bathe him from her wheelchair seat.
Although her husband disciplines Makaya, Herald said, "It's not really that unusual for me. I helped raise my two nieces who were bigger than me."
Now, Makaya helps her mother change diapers.
As for the medical bills, the couple owns a small business for used baby items, "Katari's Korner," named for their older daughter. They have health insurance.
"We do it part-time," she said. "It's hard to have a full-time anything when you have three kids," she said. "Wil and I are very independent. We don't ask for a lot of help."
Financially, Herald said, "We make it. God blessed us where we're in a position now where we can do that."
Herald said she and her husband, who is training to be a pastor, each experienced their own "miracle."
"He fell off the back of a truck and wasn't supposed to live," she said. "Doctors told my mom I wouldn't make it."
As for ignoring the doctors' advice, Herald said one of the first lessons the couple learned as her husband was taking correspondence Bible classes was about "faith."
"The more we read and the more we studied, we relied on that," she said. "We both wanted children and we believed in God, and he believed in us."
Other experts say they would never interfere with a woman's decision to have a child, despite the risks.
"We believe it's a personal decision," said Mary Beth Huber, director of programs for the Osteogenesis Imperfecta Foundation. "Many women who have bone deformity to the pelvis can carry a child and give birth."
The disability rights movement has empowered women who "a generation ago" would have never considered having a child, said Huber.