Coming just months after she and husband Paul, from Glasgow, endured the pain of a miscarriage, the pair's faith was tested to the limit.
But, they never gave up on their dream, and are now the proud parents of their "miracle" daughter, Ailith.
The unimaginable cycle of events began three years ago, when Gillian, 33, and 39-year-old Paul began trying to conceive.
Delight of finding out they were expecting soon turned to heartbreak, when, in October 2014, they learned Gillian had miscarried just two weeks after becoming pregnant.
She recalled: "We always knew we wanted a family. We were overjoyed to find out I was pregnant but when doctors told us I had miscarried it was awful."
Still locked in grief, the couple's emotions were thrown into turmoil once more when, in early 2015, Gillian tested positive again.
They were, however, to be dealt another cruel blow, when she started to feel something was amiss.
But, when a scan was arranged to check things over, Gillian and Paul's worst fears became a reality as they were told there was no sign of a baby.
"The signs were that it was a miscarriage," Gillian said. "I returned to the hospital every couple of days for almost two weeks.
"But, one day, a midwife called and said she thought it might be an ectopic pregnancy."
An ectopic pregnancy is when a fertilised egg implants itself outside of the womb, usually in one of the fallopian tubes.
With the worst confirmed, Gillian was given medication to "dissolve" her pregnancy in a fortnight.
Having gone through two unthinkable tragedies, she and Paul didn't know think anything else could go against them.
But, after Gillian began to experience excruciating pain in her shoulder - a sign of a ruptured fallopian tube - and stomach pain while out for lunch with family, she was rushed to A&E.
Given scans, she was set for a night of monitoring, however, convinced something didn't add up, Paul persisted until surgery was performed - something that proved life-saving.
Gillian said: "I have a high pain threshold, but this was unbelievable. Paul and my mum pushed for an operation - they knew something was seriously wrong. I didn't know what was going on - in the back of my mind I was still hoping for a miracle."
When medics got Gillian into theatre, they found she was bleeding internally and had to remove her right fallopian tube.
"It was terrifying but my husband was my rock - in one day he lost his baby and almost his wife."
Dealing with a double loss, Gillian and Paul didn't know where to turn, especially as they found there is so little known about ectopic pregnancies.
Gillian said: "When this happens, it feels like you leave with some painkillers but no idea what to do. I didn't know how to deal with everything, what my future held or whether I could conceive again.
"I was told my chances of getting pregnant were 75% but we were so scared - we'd lost two babies and didn't know if we could go through it a third time. Our heads were all over the place."
Thankfully, in March last year, their prayers were answered and, nine months later, "rainbow baby" Ailith arrived.
Describing the mixed emotions, Gillian said: "I was panicking the whole way through. We were at appointments and sitting in the same corridor as we were at time of the ectopic pregnancy but seeing our baby was unbelievable.
"Everyone was so supportive - the care I received at the Early Pregnancy Unit in the Queen Elizabeth University Hospital was brilliant.
"Ailith is so special. I want to wrap her in cotton wool. The grief never leaves you but she keeps us going."