Genetic testing with twins

Steph
My husband and I aren't too big on genetic testing but if we don't do the pre screening for Down syndrome within the next two weeks cause I will be 12 weeks on Monday, I won't have an ultrasound till 20 weeks and I haven't had one since 8 weeks. Anyways, my doctor said this is the only screening that I could even do since I am having twins. I didn't know if that was true.