SO HOW DO YOU GET A PANDA PREGNANT?

The female panda didn't do it all by herself, however. Much of the credit for the birth goes to veterinarian Boripat Siriaroonrat, who used male panda Chuang Chuang's sperm for the successful artificial insemination of Lin Hui in February. Both pandas are on loan from China.

Boripat is the assistant director of the Zoological Park Organisation's conservation, research and education unit, and he, along with his 20-member team, has been trying to get Lin Hui to produce a baby since 2004.

That's when the team first started testing the female panda's urine to identify the hormones that would tell them when she ovulated and was therefore in the right part of her cycle for both natural and artificial insemination.

"We have to test her urine every day because pandas normally ovulate only once a year and each ovulation lasts only three days," Boripat said. "We couldn't afford to miss the cycle. It's so short - just 72 hours a year to inseminate Lin Hui."

The team first tried natural insemination at the zoo, encouraging Lin Hui to mate with Chuang Chuang at Chiang Mai Zoo.

"Only about 5 per cent of male pandas can successfully mate with female ones naturally," Boripat said.

But the couple failed to mate, so the team switched to plan B, artificial insemination.

"Five experts from San Diego Zoo and the Smithsonian's National Zoological Park in the US trained us in the artificial insemination procedure," he said.

Boripat started the first artificial insemination in 2007 with assistance from an expert who flew in from China, but they had no success.

The team succeeded with the second insemination procedure, which was carried out in mid-February, and Lin Hiu gave birth to the female cub on the morning of May 27.

"People asked us why there had been no news that Lin Hui was pregnant or why we hadn't known exactly when the baby panda would be born.

"A pseudo- or false pregnancy is indistinguishable from a real pregnancy, and a panda ovulates whether she is pregnant or not. The influence of the progesterone hormone encourages the panda to eat more and put on weight and stimulates the teats to produce milk," Boripat explained.

His team did try to check if Lin Hui was pregnant by ultrasound, but the results were inconclusive as the panda has thick uterus walls, making it hard to find a foetus that measures 1/900th of her mother's size during gestation.

"The other method we could have used was to anaesthetise then X-ray the mother.

"It would have helped us see the cub's skull, but we decided against it because it increases the risk of abortion."

Boripat also explained that detecting a panda foetus by testing the mother's blood to identify markers for pregnancy - certain proteins and antibodies - is still under research. "Only a few countries have done this successfully so far," he said.

"Giant pandas go through big changes between 160 and 80 days prior to giving birth. A condition called embryonic diapause - where the embryo ceases to develop for a time - is common, making it difficult for veterinarians to trace the course of the pregnancy, or even confirm it.

"Embryonic diapause can last from a few days to a month or more. So no one in the world can confirm the exact day when a panda will give birth."

The cub and mother are being looked after at Chiang Mai Zoo by a team led by veterinarian Kanika Nimtrakul. It will monitor the fragile cub for the next 100 days to guard it from disease and accidents until it is able to take its first steps.

As well as overseeing Lin Hui's insemination, Boripat is conducting other assisted reproductive-technology projects.

He is working on artificial insemination projects for Eld's deer at Kasetsart University's Kamphaengsaen Campus and for small wildcats at Chulalongkorn University.