I'm the marginal age case that my doctor has not strongly recommend me to 抽羊胎水, but I did it for safety purpose.
抽羊胎水 to me is not terrible. Yr doctor just put a longer pin at yr tomy and take out some 羊胎水 around yr embryo (baby) after ultrasound checking. It takes less than 15 mins. No painful, don't be panic!!
dk486,
You may go to the Prince of Wales Hospital to join a test called OSCAR, instead of 抽羊胎水. It costs $950, and is conducted by the Professors in the Chinese University. The test included blood test, measurement of the thickness of the neck of the embryo. It has to be conducted in week 12 to 15.
More details can be found in the website of the Prince of Wales Hospital, or you can called the hospital.