The one measurement of fetal maturity that is not affected by a 'bloody tap' during amniocentesis is:
L/S ratio
Phosphatidyl glycerol
α-fetoprotein
Bilirubin as a measured by DOD 450
The best test to detect fetal lung maturity in diabetic mothers is presence of phophatidyl glycerol (PG) in amniotic fluid. If PG is present in amniotic fluid fetal lungs are considered mature and vice versa.