Q: I am 38 years old and 7 weeks pregnant. This afternoon I was asked by the doctor to opt for one of the following tests in relation to Down's syndrome- Integrated test: ultrasound examination at 10 weeks followed by a blood test at 16 weeks to measure alpha-fetoprotein and human chorionic gonadotrophin levels OR Amniocentesis. I was told that the integrated test is safer but the results are not as accurate as amniocentesis. Also I am informed that amniocentesis is risky and could cause miscarriage. I opted for the integrated test. I hope I have made the right choice. If you feel that it is better for me to undergo amniocentesis, kindly advise and I shall try to change my option.

A:Screening tests will remove about 90% of the risk, but 100% certainty of normality is provided only by amniocentesis. You should have an ultrasound study at 12-13 weeks and a blood test (first trimester biochemical screening) at about the same time.