Ultrasonically determined menstrual age as an indicator of fetal lung maturity

The usefulness of ultrasonically determined menstrual age as a predictor of fetal lung maturity has been evaluated in patients without fetal or maternal disease undergoing repeat cesarean section. The menstrual age of each fetus was determined at 18–32 wk using biparietal diameter (BPD) measurements and previously established BPD growth curves. Lung maturity prior to delivery was assessed by measuring the lecithin/sphingomyelin (L/S) in amniotic fluid. The menstrual age at the time of the amniocentesis was derived by extrapolation from the results of the first scan. When the Sabbagha Composite BPD growth curve was used for menstrual age determinations, the L/S was <2.0 in all cases before 34 wk, both <2.0 and ≥2.0 between 34 and 38 wk, and ≥2.0 in all but one case after 38 wk. This one case represents 1.2% of fetuses studied. These results suggest that in the absence of fetal and maternal disease, a menstrual age of 38 wk or older, based on an early BPD measurement and use of the Sabbagha Composite BPD growth curve, is indicative of lung maturity in most cases.     

Fetal lung maturity

Respiratory distress syndrome of the newborn infant caused by immaturity of the fetal lung continues to be a clinical problem. Measurement of pulmonary surfactant production is the most effective way to evaluate pulmonary maturity. Since the first fetal lung maturity test was described more than two decades ago, advances in methodology have produced diagnostically sensitive tests that are both rapid and precise. Unfortunately, currently available tests continue to demonstrate low diagnostic specificity and remain poor predictors of fetal lung immaturity. We review the background, methodology, pre-analytical and analytical concerns, and clinical performance of various fetal lung maturity assays, and discuss the appropriate use and interpretation of these tests.     

Characterization of amniotic fluid lamellar bodies by resistive-pulse counting: relationship to measures of fetal lung maturity

Resistive-pulse counting studies of amniotic fluid lamellar bodies are presented and demonstrate a strong concordance with the predictions of accepted measures of fetal lung maturity. Uncentrifuged as well as centrifuged specimens could be evaluated, because cells and debris are rejected electronically. The technique is not affected by bilirubin or debris of lysed whole blood, and only mildly by meconium. Lamellar body number density and mean lamellar body volume were determined for 161 uncentrifuged and 241 centrifuged specimens. Number density maturity criteria (40,000/microL and 26,000/microL, respectively) were shown to be highly concordant with established measures of fetal lung maturity; mean lamellar body volume did not extend this concordance. Since electronic cell counters are generally available 24 h per day and the approach requires neither centrifugation nor subjective interpretation and is rapid and inexpensive, it is proposed that determining lamellar body number density by resistive-pulse counting may be a useful initial screen for the assessment of fetal lung maturity.     

Fetal lung maturity assessed by fluorescence polarization: evaluation of predictive value, correction for endogenous fluorescence, and comparison with L/S ratio

The steady-state polarization (or anisotropy) of the fluorescent dye 1,6-diphenyl-1,3-5-hexatriene in amniotic fluid samples and the lecithin/sphingomyelin ratio of the samples were correlated with development of respiratory distress syndrome in newborns. We found that clinical samples have a variable endogenous fluorescence that reduces the observed polarization (or anisotropy). This background is a major interference in the assessment of fetal lung maturity by the polarization method. Correction for this interference, by also measuring the blank fluorescence and anisotropy of the sample, provides a clinical tool with a lower coefficient of variation than that of the more time-consuming lecithin/sphingomyelin ratio. The clinical correlation for 17 cases of respiratory distress syndrome in a high-risk population (60 births; twins counted as a single birth) indicates that the two methods are equivalent for predicting immature fetal lung status.     

Determination of amniotic fluid palmitic acid concentration for the estimation of fetal lung maturity

Palmitic acid concentrations in amniotic fluid (AF) were determined in 135 patients with normal and pathological pregnancies between the 27th and 42nd week of gestation. There was a sharp rise in the mean palmitic acid concentration after the 34th weeks of gestation from 2.7 μg/ml to 9.9 μg/ml at term. This increase is almost identical with the rise of AF-lecithin. It was found that between 70% and 100% of AF-palmitic acid originates from lecithin. 65 patients were delivered within 24 h after amniotic fluid sampling. 7 infants of these patients developed a respiratory distress syndrome (RDS). In all cases with RDS AF-palmitic acid concentration was far below 5 μg/ml. Assuming an AF-palmitic acid concentration > 5 μg/ml for characterising fetal lung maturity (= no RDS), there were no false negative results, but 16% false positive results. However, the determination of AF-palmitic acid concentration seems to be a most reliable method for the assessment of fetal lung maturity.     

Estimation of fractional moving blood volume in fetal lung using Power Doppler ultrasound, methodological aspects

Perfusion estimation of the fetal lung is an important predictor of its maturity and function after birth. Ultrasound (US) power Doppler has previously been used to assess the perfusion of the fetal lung, based on the mean pixel intensity (MPI) over a region-of-interest (ROI). The drawback is that the MPI is not only dependent on the amount of flowing blood, but also depth, gain and attenuation in overlying tissue layers. In this study, power Doppler images have been analysed according to a previously published method that attempts to compensate for such unwanted variations, resulting in a measure termed fractional moving blood volume (FMBV). A total of 29 singleton pregnancies with normally grown fetuses were evaluated after 35 weeks of gestation. For reliable interpatient comparisons, we found it always necessary to use a well-defined section of the fetal lung. Therefore, all scans were performed in a transverse plane of the fetal thorax with a four-chamber view of the heart, through the intercostal space. ROIs in 12 left and 17 right fetal lungs were defined (the fetal lung closest to the transducer was always examined). No differences in estimated FMBV or MPI were found between left and right lungs. Similarly, there was no significant difference between images acquired during systole and diastole. FMBV is compensated for depth and, also, for other sources of power variation, as reflected in the coefficient of variation: 0.14 for FMBV and 0.24 for MPI. A scan on a test phantom reveals that the power in dB is linearly related to velocity over a limited range, suggesting that FMBV might be useful for discriminating between normal and decreased fetal lung perfusion.     

Evaluation of the shake test to predict respiratory distress syndrome

An analysis of the relationship of amniotic fluid shake test titers and the subsequent fetal lung maturity as evinced by the development of the respiratory distress syndrome (RDS) has been conducted. Over a four-year period, 131 amniotic fluid samples were tested within 48 hours of delivery. RDS was diagnosed in 16 infants. When the shake test was positive at a 1:2 dilution, one child developed a mild case of RDS (2.3%). If the test was postivie at a 1:4 dilution, none developed RDS. RDS occurred in 15% of the cases with a positive test at a 1:1 dilution and in 30% of the cases with a negative test. This test has proved to be an excellent screening method for predicting fetal lung maturity if it is positive at 1:2 or greater. If the result is positive at a 1:1 dilution, or negative, other methods must be used for assessment. Its advantages are its rapidity, simplicity, and low cost.     

Sonographically detected free-floating particles in amniotic fluid predict a mature lecithin-sphingomyelin ratio

Amniocentesis for the determination of fetal lung maturity is associated with some morbidity, and so the prediction of a mature fetus by noninvasive means could be useful in managing certain high-risk patients. In the first portion of this study, 467 amniotic fluid specimens were classified into one of five groups based on the turbidity and particulate matter present. The mean lecithin: sphingomyelin (L/S) ratios and the proportion of mature L/S values increased with increasing turbidity of the amniotic fluid. In the second portion of this study, the presence of amniotic fluid free-floating particles (FFPs) detected by real-time ultrasound was correlated with fetal lung maturity. When FFPs were present, the L/S was uniformly mature, but when FFPs were absent, the L/S was mature in 74% of patients (P less than 0.01). Among the patients in whom the L/S ratios were mature, 39/110 were associated with positive FFPs (sensitivity = 35%). This preliminary study suggests that the presence of FFPs on real-time ultrasound could be used to confirm fetal lung maturity.     

Degree of unsaturation of the fatty acid chains of phospholipids influences the fluorescence polarization: implications for evaluating fetal lung maturity

To study the effect of fatty acid chain saturation on the fluorescence polarization assay as a measure of fetal lung maturity, we used purified phospholipids isolated from human amniotic fluid and various commercial phospholipids. We found that the fluorescence polarization value decreased as the concentration of unsaturated fatty acids increased. In contrast, the lecithin/sphingomyelin ratio increases with increasing amounts of saturated lecithin, produced as the fetal lung matures. Since only saturated lecithins are surface active, the two indices of fetal respiratory status must reflect different properties of lung surfactant.     

羊水样本卵磷脂和鞘磷脂检测超高效液相色谱串联质谱方法的建立及应用

目的建立检测羊水中卵磷脂和鞘磷脂(L/S)的超高效液相色谱串联质谱(UPLC-MS/MS)方法,以便准确、高效地预测胎儿肺成熟度。方法收集孕32~39周孕妇分娩时的羊水样本23份。依据新生儿Apgar评分标准,有3例胎儿胎肺未成熟、20例胎儿胎肺成熟。另收集孕18周孕妇羊水样本7份作为基线对照,建立检测羊水中卵磷脂和鞘磷脂水平的UPLC-MS/MS方法,计算卵磷脂/鞘磷脂(L/S)比值,同时采用板层小体计数(LBC)法检测板层小体(LB),评价2种方法在预测胎肺成熟度中的价值。结果建立的检测羊水中卵磷脂和鞘磷脂的UPLC-MS/MS方法精密度良好,离子峰强度和保留时间均在可检测范围内,主成分分析(PCA)显示6个质控样本聚类良好。以L/S比值=10作为判断胎肺成熟度与不成熟的临界值,UPLC-MS/MS的敏感性和特异性均为100%。以LB=50×10^9/L作为判断胎肺成熟度与不成熟的临界值,LBC法的敏感性和特异性分别为80%和95%。结论建立了检测羊水中卵磷脂和鞘磷脂水平的UPLC-MS/MS方法,其结果可靠,可以准确、高效地预测胎肺成熟度。     

Enzymic colorimetric determination of phosphatidylglycerol in amniotic fluid

We describe a procedure for the enzymic, colorimetric determination of phosphatidylglycerol in amniotic fluid. After extraction into chloroform:methanol (2:1 by vol) and evaporation, the phospholipid-containing residue is redissolved in a non-ionic detergent, which thus provides an aqueous sample. The subsequent enzymic reaction sequence involves phospholipase-catalyzed hydrolysis of glycerol from its phospholipid. Subsequent enzyme-catalyzed reactions phosphorylate this glycerol and oxidize the resulting glycerol phosphate to produce hydrogen peroxide, which is reacted to produce an intense red chromogen in the peroxidase-catalyzed coupling of 4-aminoantipyrine and 2-hydroxy-3,5-dichlorobenzenesulfonate. When used in conjunction with previously reported enzymic techniques for determination of lecithin and sphingomyelin, this procedure may provide an accurate and precise "lung profile" for assessment of fetal lung maturity.     

Varix of the fetal intra-abdominal umbilical vein: prenatal sonographic diagnosis and suggested in utero management.

Varix of the fetal intra-abdominal umbilical vein (FIUV) is a rare entity. We describe an ultrasound diagnosis of this condition together with a review of the literature relating to its prognosis and management. Our conclusion is that close fetal monitoring should be performed, and delivery should be induced when lung maturity has been accomplished or any fetal distress is apparent.     

Diagnosis of fetal lung maturity by ultrasound: a new method and first results.

The first results are presented of a method to determine the maturity of fetal lung by sonography. By comparing the frequency characteristics of lung echoes to those from the fetal liver as a reference organ, we avoid the known pitfalls which previously made it impossible to standardize fetal lung changes with gestation.We examined 222 patients between 27 and 39 completed weeks of gestation. In one ultrasound section we depicted fetal lung and liver simultaneously. Switching to A-mode we registered the frequencies contained in the video envelope in both organs.The registered frequencies were entered digitally in to a computer and checked for mean frequency, maximum frequency and minimum frequency. Afterwards, the ratio of the frequencies of the lung and liver were obtained. For all weeks of gestation, the mean value and standard deviation were calculated.We found the liver to be an adequate reference organ, since there is no change of the reflection pattern between the different weeks of gestation, while significant changes were registered in the fetal lungs. A quotient of Q(mean) lower than 1.1 suggests lung maturity, while values over 1.1 point to immaturity.This appeared to be confirmed in 13 patients who had agreement between amniotic fluid lecithin values and Q(mean). Further comparisons with amniotic fluid results will have to validate these findings.     

Prospective clinical evaluation of an improved fluorescence polarization assay for predicting fetal lung maturity

We performed a prospective clinical evaluation of our newly developed fluorescence polarization procedure to predict fetal lung maturity (Clin Chem 1986;32:248-54). Net fluorescence polarization was measured at 34 degrees C after a 6.5-min incubation of amniotic fluid with fluorophore. For the 26 cases of neonatal respiratory distress syndrome encountered in 196 deliveries, the net polarization exceeded 0.287 for 22 (85%) of these, and exceeded 0.260 for all 26. The specificity of the polarization assay equaled or exceeded the specificity of the lecithin/sphingomyelin ratio for all sensitivities greater than 70%. Neither assay was a good predictor of the clinical severity of respiratory distress. For a separate group of 21 amniotic fluid specimens clinically contaminated with blood or meconium, the discriminatory power of the polarization assay was decreased, but six of seven respiratory-distress cases still had polarization values greater than 0.260. We conclude that this fluorescence polarization assay is a better overall predictor of fetal lung maturity than is the lecithin/sphingomyelin ratio, and that polarization values less than 0.260 are associated with little risk of respiratory distress.     

超声评估胎儿肺脏成熟度研究进展

肺发育不成熟是早产儿死亡和新生儿患病的最常见原因。评估胎肺成熟度在围生期管理中具有重要意义,产前评价胎儿肺成熟度能够提高新生儿尤其是早产儿的存活率。超声在产前评估中发挥重要作用。本文对超声评估胎儿肺成熟度的研究进展进行综述。     

肺成纤维细胞三维立体培养条件对肺纤维化组织重塑的影响

背景：组织细胞三维立体培养是肺纤维化破坏与组织收缩研究的理想模型,特别是在纤维化的进展过程中,几种细胞因子如肿瘤坏死因子、白细胞介素、前列腺素、胰岛素以及渗出的血浆成分可能在纤维化的损伤修复和组织重塑中起重要的作用。目的：观察三维立体培养条件下肺成纤维细胞在血清和血清蛋白、胰岛素和细胞因子前列腺素E2、转移生长因子β、肿瘤坏死因子α的细胞外胶原基质收缩和细胞凋亡,探讨肺纤维化过程中细胞因子、胰岛素、血清及血清蛋白对肺组织重塑和纤维化形成的影响。设计：随机对照实验。单位：解放军兰州军区兰州总医院呼吸内科。材料：实验于2005-08/2006-01在解放军兰州军区兰州总医院呼吸内科实验室完成。人胚肺成纤维细胞（AmericanTypeCultureCollection）,DMEM培养液和胎牛血清（GIBCO）,胰岛素、转移生长因子（R＆D）,前列腺素E2（Sigma）,Ⅰ型胶原提取自大鼠尾部肌腱。方法：为观察初始浓度对成纤维细胞收缩力的影响及细胞数量对胶原收缩的影响,提取大鼠尾部的胶原,与双蒸水、4×DMEM及成纤维细胞混合成胶原含量为0.75-1.5g/L的立体组织胶原,细胞浓度为0.2×10^7-4×10^7L^-1,置入含体积分数0.05的CO2培养箱37℃培养。每天测定胶原的面积,最后计算终面积与初始面积的比值。将0.01%-0.5%血清、0.1%的血清白蛋白和0.1%球蛋白分别加入到培养液中,观察胶原的收缩。加入10mg/L转移生长因子、10mg/L白细胞介素1、1mmol/L胰岛素和0.1μmol/L前列腺素E2,观察细胞因子对成纤维细胞介导胶原收缩的影响,对胶原中DNA含量进行测定及细胞存活率检测。主要观察指标：不同细胞因子或血清成分对肺成纤维细胞介导胶原收缩的影响,胶原内成纤维细胞数量对胶原收缩的影响,以及不同浓度胶原对胶原收缩和对细胞增殖和凋亡的影响。结果：①胶原的收缩有细胞依赖性,细胞浓度越高则胶原收缩越强烈。②血清和白蛋白的加入引起了剧烈的胶原收缩。③转化生长因子和胰岛素增强胶原的收缩,前列腺素E和白细胞介素1抑制胶原的收缩。④胶原的初始浓度越低,胶原收缩的速度越快越强烈,胶原终面积就越小,其中的成纤维细胞凋亡就越多。结论：肺成纤维细胞介导的胶原收缩可被白细胞介素1和前列腺素E抑制,胰岛素和转化生长因子则促进了胶原收缩。血清及血清成分在受损肺组织的渗出可以导致肺组织胶原的稀释与强烈收缩,而导致成纤维细胞增殖的抑制和凋亡的增加,肺纤维化进一步发展,成为无细胞胶原成分。     

用免疫印迹法测定肺表面活性蛋白A及其临床应用

肺表面活性蛋白Ａ含量测定可作为胎儿肺发育成熟的指标和肺部疾病的辅助诊断，以及用于疗效观察和预后估计。本文建立了免疫印迹分析ＳＰＡ法，测定了５５例３６￣４２孕周健康产妇羊水中ＳＰＡ含量，发现随着孕周增加，ＳＰＡ含量呈上升趋势。本文还测定了２６例儿胸外科手术病人术前和体外循环时肺泡灌洗液中ＳＰＡ含量，与术前比较有明显下降，结果与临床符合，本文所建立的方法是一种敏感度高，简单实用研究肺表面活性物质的有效     

Relationship between Grade III placentas and biparietal diameter determinations

Grade III placentas were found in 133 (12 per cent) of 1,082 pregnant women evaluated ultrasonographically after 20 weeks of gestation. Associated biparietal diameter measurements ranged from 7.2 to 10 cm. In 11 women with no complications known to accelerate fetal lung maturity or to induce premature placental maturation, grade III placentas were observed between 30 and 33 weeks of gestation. Gestational ages determined according to the growth adjusted sonographic age method of Sabbagha were accurate within one to three days. Considering the risk of hyaline membrane disease at those gestational ages, a grade III placenta cannot be equated with fetal lung maturity. Criteria other than placental grading should be used to assess the pulmonary status of the fetus.     

How useful is the lung-to-head ratio in predicting outcome in the fetus with congenital diaphragmatic hernia? A systematic review and meta-analysis.

OBJECTIVE: Fetal surgery to improve lung growth comprises tracheal occlusion in selected 'high-risk' fetuses with congenital diaphragmatic hernia (CDH). Sonographically measured fetal lung-to-head ratio (LHR) is utilized to recruit candidates for fetal surgery. This study provides a meta-analysis of the evidence regarding the prognostic use of lung-to-head ratio measurements in fetal CDH. METHODS: MEDLINE, SCOPUS and ISI PROCEEDINGS databases were searched for MeSH terms: lung, head, hernia and ratio. References in retrieved studies were also searched. Studies were categorized as follows: Phase I studies measured normal fetal LHR; Phase II studies compared fetal LHR in CDH survivors and non-survivors (if LHR informed therapy decisions or LHR was not measured during the window for intervention (< 32 weeks' gestation), studies were excluded); Phase III studies used LHR to guide selection for fetal surgery (non-randomized trials were excluded); Phase IV studies measured CDH survival before and after LHR application in clinical practice. RESULTS: The one Phase I study showed that LHR varied substantially with gestation and technique. No complete studies met the selection criteria for Phase II: meta-analysis of subgroups revealed similar LHR in CDH survivors and non-survivors. A single Phase III study revealed no benefit for LHR-directed fetal surgery. No Phase IV studies were identified. CONCLUSION: The prognostic use of LHR in fetal CDH entered clinical practice prior to publication of robust normal data and is not supported by current evidence. Application of a structured approach to any 'new' prognostic test could improve its validity and clinical application.     

HPLC of phospholipids in biological fluids — application to amniotic fluid for the prediction of fetal lung maturity

Because of both the advantage of speed compared with thin layer chromatography (TLC) and the dearth of high pressure liquid chromatography (HPLC) methods for phospholipid separation, it was decided to investigate the use of HPLC with a differential refractometer as detector for the separation and quantitation of amniotic fluid phospholipids required for the prediction of fetal lung maturity.A method was devised which gave results which compared well with those from TLC both in terms of quantitation and predictive value.Despite this, the method was found to lack sufficient reliability for application to the routine clinical assessment of fetal lung maturity. The method does, however, offer a good alternative to two dimensional TLC with phosphate analysis in research work involving quantitation of phosphatidyl inositol, phosphatidyl glycerol and particularly lecithin.