The zoo said that implantation, when the fertilised egg attaches to the uterus, has not yet taken place and it could be months before it is known if a full pregnancy has occurred.
Iain Valentine, director of giant pandas for the Royal Zoological Society of Scotland, said: “Scientific data does suggest Tian Tian has conceived, however, this is not pregnancy. Giant panda pregnancies are extremely complex.
“Pregnancy begins when implantation takes place and this has not yet occurred. There are many hurdles to get through yet, so we would request that people do not get too excited at this very early stage.”
Tian Tian – the name translates as Sweetie – was artifically inseminated in March, ahead of an attempt at natural mating between the female and Yang Guang – which means Sunshine. The pandas were brought to Edinburgh from China nearly four years ago.
The insemination was carried out by a team of three vets, alongside a panda expert from China. Two previous attempts at panda mating – which can only take place at one specific time of year, when hormone levels are at a peak – have proven unsuccessful.
Breeding pandas is notoriously difficult, both in getting them to become pregnant and carrying the cub to full term. Both Tian Tian and Yang Guang have bred previously, although not with one another.
Giant pandas practise ”delayed implantation” – which means that unlike in humans, the egg is not attached until late on in the pregnancy – and they are prone to phantom pregnancies.
It is likely to be late July or August before experts know whether the panda, who has lost her last two pregnancies, is actually pregnant. If she is carrying a cub, it would be likely be born in August or September.
The pair, who are generally solitary and only meet when mating, are the first giant pandas to live in the UK for 17 years.
Malcolm Roughead, chief executive of VisitScotland, said a panda cub would be a major tourism draw for Edinburgh and Scotland.
He said: “Edinburgh Zoo is one of Scotland’s most popular paid-for attractions and following the arrival of Tian Tian and Yang Guang, visitor numbers have rocketed.
“If Tian Tian does become pregnant and goes on to have a healthy cub, excitement will intensify and images of Edinburgh Zoo will be seen across the world.
“This will generate a real buzz, not only around the zoo, but also around Edinburgh and Scotland as a whole. This global media attention is an excellent way to introduce the country to new and potential visitors from all across the globe.”
The pandas, which are on loan from China for a decade for an annual fee of around £600,000, have boosted visitor numbers at the zoo, pushing profits 53 per cent higher within the first year after their arrival.