Well-known sex change surgeon Professor S. S. Ratnam died of pneumonia at the age of 73 in a Singapore hospital on Monday evening.

Singapore became a top Asian destination for sex change operations in the 1970s and 80s after he pioneered a technique that led to Singapore's first sex change operation in the 1970s.

The late professor who performed both female-to-male and male-to-female reassignment surgery is believed to have operated on as many as 500 transsexuals between 1971 and 1991.

The author of several books including Cries from within and medical texts on obstetrics and gynecology was also responsible for several fertility breakthroughs. He gave Asia its first test-tube baby through the in-vitro fertilization process in 1983 and in 1987, the first baby in Asia was born from a frozen embryo.

Prof Ratnam received several awards including the Singapore Public Administration Gold Medal in 1977 and an ASEAN award for his contributions to Reproductive Medicine in 1991.