The IVF treatments were so expensive that Gary's father SOLD his house to help them cover the costs.
But after the safe arrival of their healthy daughter Alice, the couple say their eight year costly battle has been worth every penny.
Karen, who lives in Chesham, Buckinghamshire, says: "Not many babies come with a £40,000 price tag, but she has been worth every penny.
After so many IVF treatments we were on the verge of giving up hope of ever being parents. But now she is here with us, she has been worth the wait.
Karen, 43, a medical secretary, says: "I had thought I would fall pregnant straight away as I was young and healthy. But after nearly three years nothing had happened. So we went to see our GP who referred us for tests."
The couple were seen by fertility specialists at Chiltern Hospital. Tests revealed that Gary, 44, a retail salesman, had a low sperm count. So they decided to embark on a course of IVF treatment in August 2006.
But the treatment failed, and the couple were devastated.
Karen says: "We had been pinning all our hopes on the treatment working. We thought by having IVF it would mean that I was definitely be able to fall pregnant. When tests showed the eggs hadn't even fertilised we were just devastated."
They had their second attempt a few months later. This time the eggs were fertilised but two embryos put back into Mrs McLaren's womb but the treatment didn't work.
They then underwent a third attempt and again two embryos were put back into her womb. But again, to their despair, two weeks later they were told the treatment hadn't worked.
We really thought it had worked that time. But then two weeks later I did a pregnancy test and it was negative. It was like being on an emotional rollercoaster.
After their fourth and fifth attempts both failed, the doctors carried out more tests and then told Karen that her eggs were damaged, and they needed to start looking at using eggs from a donor.
They decided to look for a donor with similar physical characteristics to Mrs McLaren and underwent their sixth course of IVF.
The mounting costs were met by the couple's savings and Gary's father sold his house to help them pay for the treatment.
Karen says: "We were so grateful to Gary's dad for helping us out as we couldn't have afforded to pay for it all ourselves. He knew how desperate we were to become parents, so he decided to help us out.
"We were hopeful this time that it would work as we weren't using my eggs, so there wasn't any risk of them being damaged.
"But that attempt failed too. We were nearly on the verge of giving up trying. I was getting worried because I was by now over the age of 40 and any pregnancy would be more risky.
We had been through so much and it had cost thousands of pounds, that we didn't know whether we could put ourselves through any more.
The couple decided to have one last try in February last year and this time only one egg was fertilised.
Karen says: "It really was our last ditch attempt. We had spent £40,000 so far and this treatment had only produced one embryo that we could use. That one embryo was put back into my womb and we had to wait to see if it would work.
"We had already been through six failed attempts, so I thought that this was going to fail too. There was only one embryo put back, rather than two, so we had even less chance of it working."
But then two weeks later the couple got the news that had been dreaming of for eight years. Mrs McLaren was pregnant.
She says: "I just couldn't believe it. We had been through so many treatments and none of them had worked. Yet we just had this final little embryo - the only one that had fertilised in the last treatment - and it had actually worked. I couldn't believe I was pregnant after all these years of trying."
Thankfully Karen's pregnancy went smoothly and baby Alice was born in November 2010, weighing a healthy 6lb 8oz.
She says: "It was the most emotional experience when she was born. Both Gary and I couldn't stop crying when we held her for the first time.
She was born on our seventh attempt, on the 7th November, seven weeks before Christmas. She really was our little miracle.
Congratulations Karen and Gary on celebrating Alice's first baby - a milestone you once never thought you'd get to.