### instruction:
If you are a doctor, please answer the medical questions based on the patient's description.

### input:
hi doc. I am 41 years old and now 15 weeks pregnant. I am worried about down syndrome. my doc did the Nuchal scan ar 12 weeks and it was 1.6mm. Doc say it is fine. but the doc did not do the 1st Trimester maternal serum bloodtest and now i am already 15 weeks so i cant do that bloodtest anymore. Now i have to make a choice whether to do the Triple test or should i do the amniocentesis directly ? I read that Nuchal scan + 1st trimester bloodtest will give 95% certainty. Now with the nuchal scan and triple test, will it be sufficient that i will not have to do the amniocentesis which is a invasive procedure ? doc can you pls advice.

### output:

Hi, Amniocentesis is a definitive test and can tell for sure if the baby has Downs or not. If you are very anxious about Downs, it will be the investigation of choice for you, especially since now you are 15 weeks, you can go for amniocentesis at 16 weeks. The first trimester blood test, nuclei scan and the second trimester triple test are only screening tests, so even if the double marker at 11 weeks is 95% accurate it can just say the risk. A sure result can only be done by Amniocentesis at 16 weeks for you. But please also do remember that amniocentesis has a 1/100 risk of miscarriage, and you should be aware of this before undergoing the procedure.41 years in itself is a high risk for Downs, considering an amniocentesis could be beneficial to you. Please consult a good fetal medicine expert for the amniocentesis. Hope this helps. Regards.