I'm 24, but because I've had a previous pregnancy with abnormalities detected very early my GP's try to push me into having the blood test and scan regardless every pregnancy even though the risk is really low for me and the pregnancy with issues wasn't genetic or chromosomal according to the lab reports, it was just most likely a developmental problem due to a faulty egg or sperm.
I refuse the blood test, but I do have the scan, with my history every day I make it past the 8 week mark is a blessing and I'll take advantage of every opportunity to see my baby kicking and moving and hear his/her heartbeat.

In the end the choice is up to you, no one can force you to d something that you really want to do. If it would help to stay informed and stress/worry free then do what you can to make things easier for yourself xxx good luck!