Sarah, from Merseyside, was trying for another baby when doctors told her she had breast cancer.
Given only a 1% chance of conceiving, she became pregnant with baby Monty shortly after her treatment.
According to Cancer Research UK, doctors normally advise women to wait two years before becoming pregnant, due to the risks of secondary cancer. Sarah was closely monitored throughout the pregnancy because of this.
This clip is originally from BBC Radio 5 live.