The use of amniotic fluid bubble stability, L/S ratio, and creatinine concentration in the assessment of fetal maturity.
Amniotic fluid bubble stability and creatinine concentration are analyzed in relation to the L/S ratio and clinical outcome. Bubble stability by the standard method showed 20.5 per cent (31/151) initial disagreement between two laboratories, 53.6 per cent (81/151) correlation with L/S ratio, and did not correlate well with patient outcome. However, a "foamy" test, i.e., foam noticeable at a distance, in both 1:1 and 1:2 dilutions, indicated an elevated L/S ratio and mature pulmonary outcome. Amniotic fluid creatinine levels showed an estimated 5 to 6 per cent risk for RDS at levels we formerly thought to be safe (greater than or equal to 2.0 mg. per 100 ml. with maternal serum less than or equal to 0.9 mg. per 100 ml.), and has many false-negative values. Fetal maturity can be estimated with clinical data and amniotic fluid analysis. Amniotic fluid sampling is necessary in all instances where the clinical data leave a reasonable doubt of actual gestational age and in all cases for elective preterm delivery. We recommend a sequential approach to amniotic fluid analysis. First a bubble stability test (a "foamy" at both 1:1 and 1:2 dilutions indicates pulmonary maturity). If the bubble stability test is not "foamy", an L/S ratio. The risk of RDS associated with creatinine concentration makes this test unacceptable in any case of elective delivery; however, it may be useful as a weighing factor in emergency situations where phospholipid analysis is unavailable.
D000649:Amniocentesis; D000653:Amniotic Fluid / Q000032:analysis; D003404:Creatinine / Q000032:analysis*; D005260:Female; D005333:Fetus / Q000502:physiology*; D006128:Growth; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature; D007752:Obstetric Labor, Premature / Q000517:prevention & control; D010713:Phosphatidylcholines / Q000032:analysis*; D011247:Pregnancy; D011379:Prognosis; D012127:Respiratory Distress Syndrome, Newborn / Q000175:diagnosis; D013109:Sphingomyelins / Q000032:analysis*
D010713:Phosphatidylcholines; D013109:Sphingomyelins; D003404:Creatinine