Only 30 births have resulted from frozen eggs

The father's semen contained no sperm, and the mother could only ovulate with the help of drugs.

Doctors had to extract sperm from the father's testes. It took the team four hours to find just eight usable sperm.

An initial attempt to fertilise the mother's non-frozen eggs with frozen sperm was not successful, so doctors froze a number of eggs for future use.

The first attempt using both frozen eggs and sperm ended in miscarriage, but the next led to a successful birth.

Future research

The entire procedure took 16 months and cost the couple about $11,550.

However, doctors said the technique was extremely difficult and much more research was necessary before it could be used on a large scale.

Dr Noel Leong, head of the reproductive-medicine unit at KK Women's and Children's Hospital, told the Straits Times that the eggs were more difficult to freeze than sperm because they were still developing.

"The genetic material is sensitive to freezing and gets damaged easily," he added. "It is easier to freeze sperm and embryos as they are genetically complete."

The first successful birth from a frozen egg was in Australia in 1986.