不同孕期羊水间充质干细胞体外培养方法的比较

背景：以往对羊水间充质干细胞的培养多采集孕中期羊水,对妊娠其他阶段羊水进行间充质干细胞培养的研究还很少,特别是系统地对不同孕期羊水和不同培养基进行间充质干细胞培养的效果还未见报道。目的：比较不同孕期羊水中间充质干细胞体外培养的效果。方法：采用两种不同细胞培养基分别对60份妊娠时间为15~42周的羊水进行间充质干细胞的分离培养,观察间充质干细胞培养过程中生长状况及间充质干细胞培养成功率;细胞化学染色法检测间充质干细胞的化学性质;MTT法检测传代后间充质干细胞的生长曲线。结果与结论：采用含体积分数为10%胎牛血清的PRMI-1640培养基和AmnioMAXⅡ complete羊水专用细胞培养基对孕期为37~42周羊水的间充质干细胞培养成功率分别为8%和44%,孕期为21~36周羊水的间充质干细胞成功率分别为20%和60%。而孕期为15~20周的羊水用两种培养基培养成功率为100%。细胞化学染色结果显示：POX、SB（-）,ACP、PAS、AENE（＋）,而NAP有1%为（＋）,不同孕期染色结果无差异。MTT法测定羊水间充质干细胞的生长曲线呈＂S＂形。孕期在15~36周的羊水间充质干细胞可以传15代以上仍然旺盛,而孕期为37~42周的羊水间充质干细胞传10代即表现为生长缓慢。结果表明采用AmnioMAXⅡ complete羊水专用细胞培养基可以明显提高晚期羊水间充质干细胞培养的成功率。羊水的最佳采集时间为15~20周。背景：以往对羊水间充质干细胞的培养多采集孕中期羊水,对妊娠其他阶段羊水进行间充质干细胞培养的研究还很少,特别是系统地对不同孕期羊水和不同培养基进行间充质干细胞培养的效果还未见报道。目的：比较不同孕期羊水中间充质干细胞体外培养的效果。方法：采用两种不同细胞培养基分别对60份妊娠时间为15~42周的羊水进行间充质干细胞的分离培养,观察间充质干细胞培养过程中生长状况及间充质干细胞培养成功率;细胞化学染色法检测间充质干细胞的化学性质;MTT法检测传代后间充质干细胞的生长曲线。结果与结论：采用含体积分数为10%胎牛血清的PRMI-1640培养基和AmnioMAXⅡcomplete羊水专用细胞培养基对孕期为37~42周羊水的间充质干细胞培养成功率分别为8%和44%,孕期为21~36周羊水的间充质干细胞成功率分别为20%和60%。而孕期为15~20周的羊水用两种培养基培养成功率为100%。细胞化学染色结果显示：POX、SB（-）,ACP、PAS、AENE（＋）,而NAP有1%为（＋）,不同孕期染色结果无差异。MTT法测定羊水间充质干细胞的生长曲线呈＂S＂形。孕期在15~36周的羊水间充质干细胞可以传15代以上仍然旺盛,而孕期为37~42周的羊水间充质干细胞传10代即表现为生长缓慢。结果表明采用AmnioMAXⅡcomplete羊水专用细胞培养基可以明显提高晚期羊水间充质干细胞培养的成功率。羊水的最佳采集时间为15~20周。     

PCR-SSP技术对羊水细胞ABO血型的基因鉴定

目的通过PCR-SSP基因技术检测胎儿羊水细胞ABO血型基因型,产前诊断胎儿ABO血型。方法选取了6名孕16 W以上的孕妇,抽取羊水细胞并进行分离,提取羊水细胞DNA,运用PCR-SSP技术分析其ABO血型基因型,并通过出生后的脐带血的血型鉴定进行确认。结果 6例羊水标本均通过PCR-SSP方法检测出了ABO血型的基因型;该6名胎儿的脐带血的ABO血型与羊水细胞的血型一致。结论 PCR-SSP技术可以准确地检测胎儿羊水细胞的ABO血型。     

Bile acid pattern in human amniotic fluid

Individual bile acids were determined in twenty-nine amniotic fluid specimens obtained from twenty-six women between the 32nd and 41st week of gestation. Total bile acid concentration ranged from 0.4 to 4.8 mumol/l with a mean of 1.57 mumol/l. Besides the two major bile acids of man, cholic acid and chenodeoxycholic acid, 3beta-hydroxy-5-cholenoic acid was found in all, lithocholic acid in ten and deoxycholic acid in nine of the twenty-nine amniotic fluid samples. 3beta-Hydroxy-5-cholenoic acid averaged 39.8% of total bile acids during 32-37 weeks of gestation and 20.2% at term (P less than 0.01). These findings point towards important differences between fetal and adult bile metabolism and may reflect maturation of hepatic bile acid biosynthesis near term.     

Early amniocentesis and amniotic fluid organic acid levels in the prenatal diagnosis of organic acidemias

Organic acids were studied in amniotic fluids taken by early amniocentesis between 6 to 12 weeks in control pregnancies. The prenatal diagnosis of methylmalonic acidemia and propionic acidemia could be made by the measurement of methylmalonic and methylcitric acid respectively in the amniotic fluid taken simultaneously with chorionic villi at the 11th week of gestation.     

妊娠晚期羊水过少112例临床分析

目的:探讨羊水过少的相关因素及围产儿的预后。方法:采用回顾性分析方法,对妊娠晚期羊水过少112例与羊水正常100例进行对比分析。结果:羊水过少多发生在孕40周后,与胎儿宫内发育迟缓(IUGR)和延期、过期妊娠有关;羊水过少组围产儿不良预后明显高于羊水正常组(P<0.01)。结论:妊娠晚期羊水过少是胎儿宫内慢性缺氧的标志,对围产儿预后有严重影响,应加强产前监测。剖宫产是处理妊娠晚期羊水过少及降低围产儿死亡率的重要措施。     

Isotope dilution analysis of methylcitric acid in amniotic fluid for the prenatal diagnosis of propionic and methylmalonic acidemia

A stable isotope dilution assay for methylcitric acid in amniotic fluid was developed to provide rapid prenatal diagnosis of the inherited disorders propionic acidemia and methylmalonic acidemia. The method utilizes two ²H₃-labeled diastereoisomers of methylcitric acid as internal standards, isolation by liquid partition chromatography and quantitation of the trimethyl esters by chemical ionization selected ion monitoring gas chromatography-mass spectrometry. Methylcitric acid at a concentration of 0.38 ± 0.10 μmol/1 was detected in normal amniotic fluid. Highly elevated levels of 7.87 and 9.16 μmol were found in the fluids surrounding fetuses affected with propionic acidemia and levels of 1.79, 2.72 and 12.27 μmol were found for fetuses with methylmalonic acidemia. Methylcitric acid was not elevated in the amniotic fluid of a fetus heterozygous for propionic acidemia. In the five pregnancies at risk for propionic acidemia, and three pregnancies at risk for methylmalonic acidemia, the levels of methylcitric acid in amniotic fluid gave the diagnosis in all cases. Measurement of methylcitric acid in amniotic fluid therefore provides a rapid and reliable method for the prenatal diagnosis of these genetic disorders.     

First-trimester echogenic amniotic fluid in the acrania-anencephaly sequence.

OBJECTIVE: To describe the association between echogenic amniotic fluid and first-trimester fetal acrania. METHODS: Nine fetuses with acrania were examined between 11 weeks' and 13 weeks 6 days' menstrual age for the presence of echogenic free-floating particles in the amniotic fluid. Cases were classified into 3 types according to the echogenicity of the amniotic fluid: similar to (type 0), slightly greater than (type 1), and clearly more echogenic than (type 2) that of the extracelomic fluid. RESULTS: In 1 pregnancy, no free-floating particles were identified (type 0). In 6 cases, small free-floating particles scattered within the amniotic cavity were identified, making the amniotic fluid slightly more echogenic than the extracelomic fluid (type 1). In the remaining 2 cases, the amniotic fluid was homogeneously and clearly more echogenic than the extracelomic fluid (type 2). CONCLUSIONS: A high percentage (89%) of fetuses with acrania had echogenic amniotic fluid, suggesting that this finding could potentially be used as a marker of fetal acrania in the first trimester. This finding also supports the hypothesis of the transition from acrania to anencephaly, with the unprotected brain undergoing progressive destruction from the first trimester, leading to the classic finding of anencephaly in the second trimester.     

Perinatal outcome in monochorionic twin pregnancies complicated by amniotic fluid discordance without severe twin-twin transfusion syndrome.

OBJECTIVES: To assess the natural history and perinatal outcome in monochorionic diamniotic twin pregnancies with discordant amniotic fluid volume without signs of severe twin-twin transfusion syndrome (TTTS). METHODS: This was an observational study of 84 consecutive monochorionic twin pregnancies which did not meet the criteria for severe TTTS and endoscopic laser coagulation of placental anastomoses at initial presentation. The population was subdivided into two groups. Group 1 consisted of 64 pregnancies (median gestational age, 20.1 (range, 15.6-24.7) weeks) with amniotic fluid discordance and no signs of congestive heart failure in the twin with the larger amniotic fluid volume (Twin 1) and positive end-diastolic flow in the umbilical artery of the twin with the smaller amniotic fluid volume (Twin 2). Group 2 (median gestational age, 19.1 (range, 16.0-24.4) weeks) consisted of 20 pregnancies with amniotic fluid discordance and intrauterine growth restriction (IUGR) (abdominal circumference < 5th percentile) in combination with absent or reversed end-diastolic (ARED) flow in the umbilical artery of Twin 2. After exclusion of one patient from Group 1, who opted for termination of pregnancy, nine patients in Group 1 and one in Group 2 developed severe TTTS, and laser coagulation was offered. The remaining 54 pregnancies of Group 1 were compared with the remaining 19 pregnancies of Group 2. RESULTS: Fetuses in Group 1 showed significantly higher survival rates (overall survival, 100/108 (92.6%) vs. 23/38 (60%), P < 0.0001; survival of both fetuses, 49/54 (90.7%) vs. 9/19 (47.4%), P = 0.0002) and median gestational age at delivery (33.6, (range, 27.6-37.8) weeks vs. 32.0 (range, 26.9-36.3) weeks, P = 0.0457). Overall, there was a significantly higher incidence of complications, defined as necessity for intrauterine intervention, fetal or neonatal death or delivery prior to 32 weeks, in Group 2 (Group 1: 30/63 (47.6%); Group 2: 16/20 (80%), P = 0.0188). CONCLUSIONS: Our data suggest that amniotic fluid discordance in monochorionic diamniotic twin pregnancies in combination with IUGR and umbilical artery ARED flow in one fetus represents an extremely high-risk constellation for adverse pregnancy outcome.     

人羊水间充质干细胞分离培养方法的优化

背景：目前关于人羊水间充质干细胞的体外分离培养方法不一,获得较多数量的间充质干细胞仍有困难。目的：分离80份羊水标本,比较不同的体外培养方法,优化筛选到一种合适的培养纯化条件,为人羊水间充质干细胞的基础研究和临床广泛应用奠定基础。方法：无菌条件下采集足月分娩和终止妊娠引产的羊水,分离羊水细胞,比较孕期、不同培养基、接种密度、首次换液时间对人羊水间充质干细胞原代培养过程的影响,通过细胞化学染色方法检测细胞代谢情况,观察人羊水间充质干细胞的生物学特性。结果与结论：相同培养条件下,采用AmnioMAXⅡcomplete羊水专用细胞培养基,以5×104/cm2的密度接种,首次换液时间为6d时,人羊水间充质干细胞原代培养成功率较高。孕期为14～20周的人羊水间充质干细胞培养成功率高于晚期妊娠（21～36周）及足月分娩（37～42周）的羊水。人羊水间充质干细胞强表达过碘酸-雪夫、酸性磷酸酶、酸性α-醋酸萘酚酯酶染色,弱表达中性粒细胞碱性磷酸酶,不表达过氧化酶、苏丹黑染色。提示,优化筛选到一种合适的人羊水间充质干细胞培养纯化条件。     

Amniotic fluid alpha-fetoprotein determination at the time of genetic amniocentesis: has it outlived its usefulness?

The purpose of this retrospective study was to evaluate the utility of routine measurement of amniotic fluid alpha-fetoprotein levels at the time of second trimester genetic amniocentesis (mean gestational age, 17.3 weeks +/- 2.5 weeks standard deviation; median, 16.8 weeks; range, 15 to 22 weeks). During the study period 7174 patients underwent second trimester genetic amniocentesis. Outcome data were available in all cases. In 79 (1.1%) cases the amniotic fluid alpha-fetoprotein level was > or = 2.0 multiples of the median. Thirty-three of the 79 (42%) patients had normal ultrasonograms, and in 31 of 33 (94%) the amniotic fluid alpha-fetoprotein level was between 2.0 and 3.0 multiples of the median. Forty-six of the 79 (58%) patients had abnormal ultrasonographic findings, and of these, 82% were neural tube defects, abdominal wall defects, or cystic hygromas. Acetylcholinesterase was positive in 37 cases, all of which had abnormal ultrasonographic findings. None of the fetuses with negative findings on sonographic screening had detectable abnormalities at birth. In this study, with over 7000 patients, amniotic fluid alpha-fetoprotein and acetylcholinesterase levels did not increase the detection of fetal abnormalities. On the basis of these results, routine measurement of amniotic fluid alpha-fetoprotein level at the time of routine genetic amniocentesis (15 to 22 weeks) does not appear justified.     

N-Acetyl-beta-hexosaminidase isoenzymes of amniotic fluid and maternal serum. Their relevance to prenatal diagnosis of the GM2 gangliosidoses.

The isoenzymes of N-acetyl-beta-hexosaminidase were quantitated in 30 amniotic fluid and 13 maternal serum samples collected between 11 and 40 weeks of gestation using DEAE-Sephadex A-25 chromatography. Isoenzymes A and B consitituted the major components of most amniotic fluids but seven samples characterized by high N-acetyl-beta-hexosaminidase activities contained high proportion of an isoenzyme apparently identical to isoenzyme P of maternal serum. This passage of maternal serum N-acetyl-beta-hexosaminidase into the amniotic cavity could lead to false negative diagnosis of type B and type O GM2 gangliosidoses if the diagnosis rely solely upon isoenzyme analysis in amniotic fluid. However, the release of maternal enzyme into amniotic fluid seems to be restricted to the third trimester of gestation and should not interfere with prenatal diagnosis of the GM2 gangliosidoses ususally performed at an earlier stage of gestation.     

Fetal Exposure to Altered Amniotic Fluid Glucose, Insulin, and Insulin-Like Growth Factor�CBinding Protein 1 Occurs Before Screening for Gestational Diabetes Mellitus

OBJECTIVE

We explored the possibility that perturbations in amniotic fluid glucose, insulin, and insulin-like growth factor–binding protein 1(IGFBP1) and/or metabolic acids exist before routine screening for GDM.

RESEARCH DESIGN AND METHODS

We selected consenting mother-infant pairs (n = 408) who met our inclusion criteria (singleton pregnancy, no genetic abnormalities, and no preexisting diabetes) and for whom sufficient amniotic fluid and appropriate medical information were available. We compared birth outcomes and second trimester amniotic fluid glucose, insulin, IGFBP1 concentrations, and amniotic fluid lactic, β-hydroxybutyric, and uric acids of mothers with gestational diabetes mellitus (GDM) (n = 52) with those of mothers with no diagnosis of GDM at >24 weeks (n = 356).

RESULTS

Higher amniotic fluid glucose, lactic acid, uric acid, and insulin and lower IGFBP1 concentrations were present by 15.1 ± 0.1 weeks in mothers in whom GDM was subsequently diagnosed. However, logistic regression showed that second trimester amniotic fluid glucose, but not insulin, IGFBP1, or metabolic acids was associated with an increased odds ratio (1.2 [95% CI 1.052–1.338]) for diagnosis of GDM at 24–28 weeks. In addition, probability contour maps that accounted for nonlinear relationships among the dynamically changing amniotic fluid constituents showed an increased risk for GDM with elevated second trimester amniotic fluid glucose in combination with either elevated amniotic fluid insulin or low amniotic fluid IGFBP1

CONCLUSIONS

Fetuses are exposed to increased amniotic fluid glucose before 15 weeks of gestation, suggesting that metabolic perturbations are underway before diagnosis and that earlier screening and intervention may be warranted.Gestational diabetes mellitus (GDM) is defined as a state of hyperglycemia arising during gestation that leads to increased glucose delivery to the developing fetus. Glucose is considered to be the principal metabolic fuel and supplies 50–80% of fetal glucose needs (1) with amniotic fluid supplying another 10–15% via fetal swallowing (2). Reportedly, amniotic fluid glucose concentrations are higher in mothers with type 1 or type 2 diabetes than in those without diabetes (3) and in those with GDM than in those without GDM (4). Amniotic fluid insulin is also elevated in mothers with GDM versus those without GDM (4–6). Some have suggested that amniotic fluid insulin may be a more sensitive early predictor of GDM than amniotic fluid glucose, but neither has emerged as an early screening tool (4). More recently, perturbations in insulin-like growth factors and their binding proteins have been implicated in diabetic pregnancies (7). In particular, lower concentrations of insulin-like growth factor–binding protein 1 (IGFBP1) in maternal plasma during the second trimester before diagnosis of GDM (8) and an inverse relationship with cord blood IGFBP1 of mothers with GDM at term and birth weight (9) have been described.It is well known that GDM is associated with poor perinatal outcomes, with macrosomia, and with a higher prevalence of diabetes in the offspring of mothers with GDM (10,11), but how soon during development these fetal insults begin is not clear. Two recent studies have linked subsequent diagnosis of GDM with irreversible oxidative damage to amniotic fluid albumin (12) and to lacticacidemia and fetal hypoxia in cord blood at term even in mothers with well-controlled GDM (13). Mothers with GDM also show evidence of altered ketogenesis and higher circulating concentrations of β-hydroxybutyrate that may be linked to increased gluconeogenesis and not to β-oxidation (14) and to increased uric acid (15) that could be related to hypoxia that often occurs with diabetes.GDM is usually diagnosed between 24 and 28 weeks of gestation by an oral glucose tolerance test (OGTT) (16). In this study, we explore the possibility that early fetal exposure to perturbations in second trimester amniotic fluid glucose, insulin, and IGFBP 1 and/or amniotic fluid lactic, β-hydroxybutyric, and uric acids may exist before current routine screening for GDM.     

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.     

Correlation between fetal gastric size and amniotic fluid volume

PURPOSE: Since abnormal conditions of the fetal digestive tract may alter both amniotic fluid volume and fetal gastric volume, we sought to determine whether amniotic fluid volume is correlated with fetal gastric volume in normal pregnancy. METHODS: A total of 280 fetal gastric size measurements were made prospectively from routine sonographic examinations of women with normal singleton pregnancies between 16 and 42 weeks of gestation. The fetal stomach was defined as the largest area including the pyloric site on transverse or oblique real-time sonographic scans. Gastric volume was calculated according to the formula for a prolate ellipsoid. The amniotic fluid index (AFI) was used for the evaluation of amniotic fluid volume. RESULTS: Both fetal gastric volume and AFI were significantly correlated with gestational age (R2= 0.422 and R2= 0.128, respectively). Only a weak correlation was found between gastric volume and AFI (R2= 0.036, p <0.001). On multivariate linear regression analysis adjusting for gestational age and fetal biometric measurements, gastric volume was not an independent and significant predictor of AFI. CONCLUSIONS: Although sonographically determined fetal gastric volume measurements appear to be useful in the assessment of fetal digestive tract anomalies, fetal gastric volume has no clinically significant effect on the amniotic fluid volume in normal pregnancy.     

Ultrasonographic demonstration of floating particles in amniotic fluid

This prospective study of 131 pregnant women was designed to determine the incidence and significance of floating particles in amniotic fluid. Floating particles ranging in size from 1 to 5 mm were seen in the amniotic fluid of pregnant women at 15 to 40 weeks' gestation. Since vernix is rarely present before 35 weeks' gestation, a source other than flakes of vernix must be sought to explain the floating particles in amniotic fluid in early gestations. There was no significant difference in the sizes or numbers of particles at different gestational ages (from 15 to 40 weeks). Therefore, it is concluded that ultrasonographic demonstration of floating particles in amniotic fluid cannot be considered an indicator of fetal maturity.     

Exhaled nitric oxide concentration and amniotic fluid nitrite concentration during pregnancy

Abstract. We have assessed fetal and maternal nitric oxide (NO) production in pregnancy. Exhaled NO and amniotic fluid nitrite concentrations were measured by chemiluminescence between 10 and 42 weeks of pregnancy. Exhaled NO concentrations did not alter significantly during gestation. In contrast, there was a significant change in mean amniotic fluid nitrite concentration in late pregnancy ( P < 0.001). The finding of decreased amniotic nitrite concentrations after 37 weeks of gestation support the hypothesis that reduced NO production may contribute to increased uterine activity in late pregnancy.     

Amniotic fluid phospholipids and foetal lung maturation

An analysis was made of samples of amniotic fluid from 82 pregnant women with normal pregnancies, ranging from 29 to 40 weeks of amenorrhoea. Lipid extraction was quantitative and individual phospholipids were isolated by two-dimensional chromatography. The lecithin/sphingomyelin ratio (L/S) increased significantly (t = 2.17; p less than 0.05) between 35 and 36 weeks of amenorrhoea (from 2.9 +/- 1.0 to 4.3 +/- 1.7). Phosphatidyl-glycerol (PG) was detected from 35 weeks of pregnancy, the time at which the incidence of amniotic samples with mature surfactant (L/S greater than or equal to 2.7 and presence of PG) was 9%; mature surfactant incidence increased to 55.5% at 36 weeks and 100% at 37 or more weeks. There was a good correlation between surfactant levels in amniotic fluid and new-born respiratory function.     

Improved immunoassay for the determination of surfactant protein A (SP-A) in human amniotic fluid

A simple, improved immunoassay for the determination of human surfactant protein A (SP-A) in human amniotic fluid was developed. The immunoreaction with a monoclonal antibody PC6-immobilized plastic bead, peroxidase-labeled monoclonal antibody PE10 and amniotic fluid sample diluting in the buffer containing 0.6% sodium dodecyl sulfate/2% Triton X-100, was carried out simultaneously at 45 degrees C for 30 min in test tubes. After washing the bead with 2% skimmilk in phosphate buffered saline containing 1% Triton X-100, the peroxidase reaction was developed by adding the substrate reagent and the absorbance was measured. The amniotic fluid obtained at full term was used as a standard instead of purified SP-A, because of the stability of the antigenicity. This immunoassay method was used to measure SP-A in 69 samples of amniotic fluid from 22 to 41 weeks of gestation. The result indicated that the SP-A values obtained by the present immunoassay can be used for predicting the fetal lung maturity. This simplified monoclonal immunoassay completed the measurement within 1 hr, and so it could be used routinely in clinical laboratory.     

Immunoassay for the determination of surfactant apoprotein (SP-A) in human amniotic fluid: comparison with other indices of assessing foetal lung maturity.

The concentration of the major surfactant-associated protein SP-A (28-36 kDa) was determined in 73 amniotic fluid samples obtained from normal (n = 40) and complicated (n = 33) pregnancies. Lecithin/sphingomyelin (L/S) ratio and phosphatidylglycerol (PG) levels were also determined in all the samples by one-dimensional step-wise thin-layer chromatography. An enzyme-linked immunosorbent assay was used to determine human lung surfactant apoprotein SP-A. The amount of SP-A in human amniotic fluid increased as a function of gestational age from 8 mg l-1 at 36 weeks to 11.75 mg l-1 at 40-41 weeks of gestation. There was a significant difference (p less than 0.01) in amniotic fluid SP-A concentration from female (9.93 +/- 0.60 micrograms ml-1) compared to male (9.10 +/- 0.52 micrograms ml-1) foetuses. In amniotic fluid samples obtained from a group of complicated pregnancies, SP-A levels were significantly lower than in the normal group when adjusted for gestational age and sex of the foetus (p less than 0.05).     

Positional fatty acid composition in total and acetone-precipitated amniotic fluid lecithin.

The fatty acid composition of lecithin has been determined separately at the 1- and 2-position in 22 samples of amniotic fluid. Palmitic acid (16:0) was the main fatty acid present at both carbon atom positions throughout the last trimester. Myristic acid (14:0) was present in very small amounts only. There was no evidence of 1-palmitoyl/2-myristoyl lecithin being present in more than trace amounts before 35 weeks of gestation. The positional specificity of the methylation pathway is therefore doubtful. Acetone precipitation of lecithin did not alter the observed fatty acid composition at either position, indicating that this procedure precipitates the different lecithin subspecies in equal proportion, without any preference for disaturated species. This method therefore fails to isolate a lecithin fraction with a specific fatty acid composition.