Birth Defect Scans?

brockerln

DH and I are trying to decide which birth defect scan to choose.  We were given three options:

1. Ultra-screen at 11-13 weeks, Maternal Serum AFP at 15-20 weeks, and detailed anatomy ultrasound at 18-20 weeks.

2.Maternal Serum AFP at 15-20 weeks, and detailed anatomy ultrasound at 18-20 weeks.   

3. Detailed anatomy ultrasound at 18-20 weeks.   

 The first has the best ability to detect chromosomal disorders like down's syndrome, and more importantly Trisomy 18.  Has anyone else been given these options, and if so, what did you decide to do?  I'm leaning towards option 1 since my insurance covers most the cost and as I understand, they are not invasive so while not harm the LO.  My hospital is also affiliated with The Johns Hopkins, so I trust their equipment is up to snuff.