It took 10 home pregnancy tests to convince Jessie McDonald that she might be carrying a baby - and even after confirmation by a doctor she still struggled to believe it.

Born with the rare genetic condition campomelic dysplasia, Ms McDonald is of short stature, at 134cms, and her spine is shaped like an S, severely compressing her chest. Long told she was infertile, she did a pregnancy test only to appease her new partner.

Jessie McDonald with her 'miracle' daughter, Alison. Credit:Paul Jeffers

''I flipped. I just didn't believe it at all. It probably took me three months to really believe it, and even then I thought it was going to be a really rocky road and it was unlikely she was going to make it because of my body,'' she said.

Ms McDonald was warned of the considerable risks she and her unborn child would face if she proceeded. With her lung function at just one quarter of a normal adult's, doctors worried that the expanding foetus would cause breathing difficulties for Ms McDonald. The baby also had a 50-50 chance of inheriting Ms McDonald's condition.