According to one web site, "The loss rate for the pregnancy has traditionally been quoted to be approximately 1: 200 procedures. More recent data, however suggest the risk of amniocentesis is actually substantially lower in the modern era of ultrasound and using modern techniques. Two recent trials have substantiate this claim. The FASTER trial was a large study of over 35,000 women that suggested the pregnancy loss rate of baseline loss rate was actually more like 1: 1600 or 0.06%. In another recent publication by Odibo, they determined in over 51,000 procedures they loss about 1: 769. This again is far less than traditionally quoted loss rates, and should be reassuring to patients contemplating such procedures."
As for the lung development of your baby, no one will know for sure how its lungs are until the test is done. But, in pregnancy, one week can make a huge difference in the development of a child, so the longer you are able to carry your child, the better.
Best of luck to you and Zadian.