This miracle baby was born twice.

When Margaret Boemer went in for her routine 16-week ultrasound she was shocked by what doctors saw on the screen.

Her third child, a girl, had a tumour, a sacrococcygeal teratoma. This rare tumour develops before birth and grows from a baby’s tailbone.

Margaret Boemer, from Texas in the US told CNN that the diagnosis was a shock.

“They saw something on the scan, and the doctor came in and told us that there was something seriously wrong with our baby and that she had a sacrococcygeal teratoma,” Boemer said.

“And it was very shocking and scary, because we didn’t know what that long word meant or what diagnosis that would bring.”

Margaret Boemer was 23 weeks pregnant when she first 'gave birth'. Via Facebook.

The tumour is more common in girls than boys and is relatively rare, occurring in only one out of every 35,000 births.

At first the advice wasn’t what Margaret and her husband had hoped for, they were told to terminate their baby, but a consultation with Dr Darrell Cass, co-director of Texas Children's Fetal Center brought a different option.

They could remove the baby and operate. Essentially Margaret would give birth at 23 weeks, and then if all goes well the baby would be returned to her uterus and Margaret would continue her pregnancy.

Margaret was told she didn’t have many other choices as the tumour was trying to grow by sucking blood flow from the baby, blood needed from the baby to survive.

"In some instances, the tumour wins and the heart just can't keep up and the heart goes into failure and the baby dies," said Dr Cass.

Margaret told CNN: "At 23 weeks, the tumour was shutting her heart down and causing her to go into cardiac failure, so it was a choice of allowing the tumour to take over her body or giving her a chance at life.

"It was an easy decision for us: We wanted to give her life."

At 23 weeks and five days, Margaret braced herself for surgery. She was told it would not be easy and the baby's chances of survival could be slim.

Dr Cass said baby's operation was the easiest part.

"The part on the foetus we do very, very quickly," he said.

"It's only 20 minutes or so on the actual foetus."

The majority of the five-hour operation was spent opening the uterus, "a big muscle lined with membranes".

Margaret and her three daughters. Via Facebook.

Dr Cass said they were confronted with a tumour so large a "huge" incision was needed to get to it.

“Essentially, the foetus is outside, like completely out, all the amniotic fluid falls out, it's actually fairly dramatic," said Dr Cass.

Once the uterus was opened up the baby was removed from her mother’s womb, the tumour was removed from her spine, then she was placed back in her mother’s womb.

At one stage the baby’s heart slowed to a dangerous rate, but the cardiac surgeon managed to transfuse the right amount of liquid to allow Dr Cass and his team to continue.

Lynne Hope survived and is now thriving. Via Facebook.

The baby girl, named Lynlee Hope, was then placed back inside and she was sealed away for another 12 weeks before she was re-born by C-section.

After she was born, there was one more obstacle to overcome, the baby needed another surgery to remove some left over tumour that the surgeons could not remove.

"At eight days old, she had more surgery, and they were able to remove the rest of the tumour," Margaret told CNN.

She recovered in the ICU and several weeks later, LynLee was allowed to go home.

Her surgeons said that she has recovered well.

"Baby Boemer is still an infant but is doing beautiful," Dr Cass said.

It's been a long journey for the family, with two births for Lynlee, but with this happy ending she truly is a medical miracle.