PrefacePulmonary surfactant(PS) is a lipid-protein mixture. It is mostimportant to maintain pneumonic function. It can reduce surface tensionon alveolar fluid-gas surface. PS is consisted of 90% lipid and 8-10%protein, which is the surfactant protein(SP). There has been fund foursorts of SP, including SP-A,SP-B,SP-C and SP-D. SP-A has been fundfirstly and expressed most intensively in type Ⅱ alveolar cell. Notonly its function is multiple, but also its characteristic on biology iscomplex, its clinic value is significant. Presently the study in relation toSP-A and diseases has been reported much more, but on SP-A levels incord blood and amniotic fluid is infrequency. There is no domesticreports on this aspect.It was reported that SP-A level in amniotic fluid is the symbol ofPS maturity. Amniocentesis can't been done for various cause, so westudy on correlation of SP-A level in cord blood between that of inamniotic fluid and expect that SP-A level in cord blood will become thesymbol of PS maturity instead of its in amniotic fluid. As well as weresearch factors that influence SP-A levels in cord blood to discuss itsdirective significance on pediatrics and obstetrics.It has been reported that PS substitutive therapy has been appliedinto newborn lung diseases. The other objective is to determine normalreference rang of SP-A in cord blood at different gestational age toprovide theory foundation of PS substitutive therapy on newborn lungdisease.Patients and methods75 newborns were selected to obtain their serum from umbilicalvein after birth at gestational age weeks 36-41 with birth weight 2430-4150g except abnormal newborns. The serum from their mothers wasobtained before delivery 24 hour and the third day after delivery,theamniotic fluid was from amniocentesis or from the progress of cesareansection. At the same time we observed and registered the factors ofmother, perinatal period and newborn.Using the method of isolating and purifying to distill SP-A. Usingthe method of western-dot blot to determine the levels of SP-A ofsamples.ResultsThe levels of SP-A( ±s) in cord blood was 24.72±10.02 ng/mlafter labor at gestational weeks 36-38, and 34.25±13.65 ng/ml atgestational weeks 39-41. The level of SP-A in cord blood was26.89±10.42 ng/ml following cesarean section at gestational weeks 39-41. SP-A levels in maternal blood before and after delivery andamniotic fluid were 42.33±18.21 ng/ml, 50.60±21.48 ng/ml and10448.65±5102.2 ng/ml.There was a correction between SP-A in amniotic and in cordblood(r =0.74). Neonatal serum SP-A was not correlated with maternalSP-A level. The SP-A level in maternal blood after delivery werecorrelated with, but higher than those before delivery(r =0.79).The level of SP-A was influenced by gestational age, birth weight,mode of delivery, etc.ConclusionThe normal reference rang( -1.96s～  1.96s) of SP-A in cordblood was 5.07～44.36 ng/ml after labor at gestational weeks 36-38,and 7.04～61.01 ng/ml at gestational weeks 39-41.The level of SP-Ain cord blood was 6.47～47.30 ng/ml following cesarean section atgestational weeks 39-41.The SP-A level in maternal blood after delivery were correlatedwith, but higher than those before delivery. SP-A normal referencerang in maternal blood before and after delivery and amniotic fluidwere 6.65～78.02 ng/ml, 8.50～92.70 ng/ml and 448.2～20449.1ng/ml.The factors that influenced the level of SP-A in cord bloodincluded gestational age, birth weight, mode of delivery, etc. Therewas complicated relation among these factors.The level of SP-A in cord blood was much correlative with that ofin amniotic fluid, but was not correlated with maternal SP-A level. Thelevel of SP-A in cord blood can become the level symbol of newborn'slung maturity instead of that of in amniotic fluid.The method we established is a highly sensitive, simple, practicaland being an effective tool by means of non-invasive for clinical using.