The Richardson Quadruplets:

Nicola and Stuart Richardson, from Nailsea, near Bristol, had been trying to conceive for years and eventually turned to IVF for help. But just as the treatment worked, the couple conceived naturally too, resulting in a surprise set of quads. The babies, who celebrate their first birthday later in January, are thought to be the only such quads in the world. Fertility treatment The couple spent six years trying for a baby before deciding to have fertility treatment. Then, 18 months ago, the couple conceived one set of twins naturally - at the same time as having a successful IVF treatment. Liz Corrigan, of Bristol University's Centre for Reproductive Medicine, said: "There can only be one explanation. "When we put the embryos back, two other eggs, which must have been in her pelvis, fertilised and resulted in these other two babies. "They were, in effect, a natural conception. It was not until Mrs Richardson's doctor found four heartbeats instead of two on a scan, that the couple realised anything unusual had happened. Despite worries over the risks of a multiple pregnancy, Mrs Richardson went on the carry all four babies - named Anna, Ben, Matthew and Harry - to term. She said: "We thought twins would be hard enough work. But miraculously we ended up with quads. They are our miracle babies.They are all different - they all have different personalities but it is amazing to watch the way they interact." Mrs. Richardson added: "They cost a fortune - nappies alone cost £400 a month, but thankfully we are sponsored, otherwise we would be bankrupt."