More than four months after Jia Jia was artificially inseminated, it is still not clear if the giant panda is pregnant.

Ultrasound scan results so far have been inconclusive, said Wildlife Reserves Singapore (WRS) at a media conference yesterday.

Jia Jia, which celebrated its seventh birthday yesterday at the River Safari, was artificially inseminated on April 18, after a mating attempt with panda Kai Kai failed.

WRS, which runs the River Safari, said Jia Jia's caretakers would know for sure by late next week if the panda is pregnant.

If not, the safari will look to next year for another attempt at mating.

Dr Cheng Wen-Haur, chief life sciences officer at WRS, said there is only a slim chance that Jia Jia is pregnant.

Since July, the panda has been eating less bamboo, sleeping more and spending more time in its den. Its hormone levels are increasing as well. This happens during pregnancy or pseudo-pregnancy.

It is quite hard to detect a panda's foetus, as it is small and starts to develop only a few weeks before birth. The gestation period for a panda is typically five months, and results in one or two cubs.

"We can only definitively conclude she is not pregnant once her hormone levels return to normal and she has not delivered," said Dr Serena Oh, assistant director of veterinary services at WRS. "For now, it is still a guessing game."

The giant pandas celebrate their third anniversary at the River Safari with a Panda Party Week starting this weekend, from Sept 5 to 13. Kai Kai turns eight on Sept 14.

Visitors can look forward to interactive booths to learn more about the animals. Children aged seven and eight can enter the River Safari for free this month, to mark the pandas' coming of age.