AN obstetrician and three Prince of Wales Hospital doctors are being sued by a woman who gave birth to a baby diagnosed as having Right Erb's palsy. In a writ filed in the Supreme Court, Chung Koon-man, three, and his mother, Lai Kwai-heung, have named consultant Christopher Haines, Li Chi-yin, Fung Tak-yuen and Jackson Woo as defendants. On July 21, 1990, Ms Lai, a diabetic, was admitted to the hospital for assessment and control of her high blood sugar and for delivery. About a month later she delivered and the baby was diagnosed as suffering from Right Erb's palsy (paralysis). The plaintiff claims this was caused by the negligence of the defendants. The writ states that despite attempts made at the hospital, Ms Lai's diabetes was never under control. She is claiming special damages of about $60,000, interest and costs. Ms Lai lives with her family in Tin Ping Estate, Sheung Shui.