Use of the amniotic fluid index combined with estimated fetal weight within 10 days of delivery for prediction of macrosomia at birth.

OBJECTIVE: The purpose of this study was to assess the value of combining the sonographically estimated fetal weight (EFW) and amniotic fluid index (AFI) measured within 10 days of term delivery for prediction of macrosomia at birth. METHODS: Prospective sonographic fetal biometric measurements and delivery ward data of a single center, uploaded separately over a 4-year period, were retrospectively linked to yield an unselected sample of nondiabetic pregnancies with live-born term neonates. RESULTS: Of the 1925 pregnancies evaluated, 140 (7.2%) were macrosomic (birth weight > or =4000 g). The AFI was significantly higher in the macrosomic group (P < .001). On receiver operating characteristic curve analysis, the area under the curve was larger for predictions based on the EFW alone than on the AFI. An EFW of 4000 g or higher had a positive predictive value of 46.6% for macrosomia at birth. Use of the previously suggested combined EFW and AFI cutoffs of 3689 g and 119 mm, respectively, yielded a positive predictive value of 30.3%. CONCLUSIONS: Combined use of the EFW and AFI rather than the EFW alone does not improve prediction of macrosomia at birth.     

Effect of fetal movement on the amniotic fluid index in diamniotic twin gestations

Fetal movement changes the size and location of amniotic fluid pockets during measurement of the amniotic fluid index. In singleton gestations, the effect of redistributing the fixed intrauterine fluid volume on the amniotic fluid index is clinically insignificant. In this study, we tested the hypothesis that the index in twin pregnancies is unaffected by fetal movement. A single examiner prospectively determined the amniotic fluid index before and after three discrete episodes of movement by both fetuses of 82 diamniotic twin pregnancies referred for obstetric sonograms between 20 and 38 weeks' menstrual age. A reliable blinded examiner provided a second post-movement measurement as a control. Data were analyzed by the paired t-test. The mean change in the amniotic fluid index after fetal movement was 2.1 ± 0.2 cm and 3.7 ± 0.3 cm for post-movement determinations by the same and blinded examiners, respectively (p < .001). Interobserver variation was 3.5 cm. Intraobserver variation was 1.8 cm for the first examiner and 2.2 cm for the second examiner. Therefore, interobserved and intraobserver variation can account for the observed change in the amniotic fluid index following movement of both diamniotic twins. © 1997 John Wiley & Sons, Inc. J Clin Ultrasound 25:255–257, 1997     

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.     

羊水量异常的超声诊断与胎儿畸形的关系

目的 探讨羊水量异常与胎儿畸形的关系.方法 回顾分析2004年3月至2006年11月在本院进行二维及三维超声检查34 900例20周以上的胎儿,其检出羊水量异常160例,并研究分析羊水量多少与胎儿畸形的关系.结果 160例羊水量异常中,羊水过多100例,羊水过少60例,二者畸形的发生率分别为37%、31.6%.结论 超声是诊断羊水量异常的首选方法,而且还能发现胎儿畸形,进一步证明羊水量异常与胎儿畸形的发生密切相关.     

Amniotic fluid and the clinical relevance of the sonographically estimated amniotic fluid volume: oligohydramnios

The amniotic fluid volume (AFV) is regulated by several systems, including the in-tramembranous pathway, fetal production (fetal urine and lung fluid) and uptake (fetal swallowing), and the balance of fluid movement via osmotic gradients. The normal AFV across gestation has not been clearly defined; consequently, abnormal volumes are also poorly defined. Actual AFVs can be measured by dye dilution techniques and directly measured at cesarean delivery; however, these techniques are time-consuming, are invasive, and require laboratory support, and direct measurement can only be done at cesarean delivery. As a result of these limitations, the AFV is estimated by the amniotic fluid index (AFI), the single deepest pocket, and subjective assessment of the AFV. Unfortunately, sonographic estimates of the AFV correlate poorly with dye-determined or directly measured amniotic fluid. The recent use of color Doppler sonography has not improved the diagnostic accuracy of sonographic estimates of the AFV but instead has led to overdiagnosis of oligohydramnios. The relationship between the fixed cutoffs of an AFI of 5 cm or less and a single deepest pocket of 2 cm or less for identifying adverse pregnancy outcomes is uncertain. The use of the single deepest pocket compared to the AFI to identify oligohydramnios in at-risk pregnancies seems to be a better choice because the use of the AFI leads to an increase in the diagnosis of oligohydramnios, resulting in more labor inductions and cesarean deliveries without any improvement in peripartum outcomes.     

The fetal gastrointestinal tract is exposed to melatonin and superoxide dismutase rich amniotic fluid throughout prenatal development

Amniotic fluid (AF) is the first fluid to enter the gastrointestinal tract. Preterm birth is leading to a sudden interruption of AF swallowing. Understanding the composition of amniotic fluid is crucial to implement strategies preventing intestinal injury in preterm infants. We hypothesized that the fetal gastrointestinal tract (GIT) is exposed to melatonin and antioxidant enzymes via amniotic fluid throughout prenatal development. Amniotic fluid samples from 76 pregnant women with a median (range) gestational age of 38.0 (14.3–40.1) weeks have been collected. Immediately after birth blood samples were collected from the umbilical vein (n = 53). Median (Interquartile range) melatonin concentration was 30.5 pg/ml (12.7–118.3) and superoxide dismutase 1 (SOD1) concentration was 84 ng/ml (59–123). Extracellular glutathione peroxidase concentration was either not detectable or exceptionally low. We found a positive correlation between melatonin concentration in amniotic fluid and gestational age (Spearman’s correlation coefficient, r = 0.570, p<0.001), while SOD1 concentration in amniotic fluid was inversely correlated with gestational age (r = −0.246, p = 0.032). Compared to serum samples, melatonin concentration was statistically significantly higher in amniotic fluid (p<0.001). Our results indicate that the fetal gastrointestinal system is continuously exposed to melatonin and SOD1 via the amniotic fluid throughout prenatal development.     

The effects of maternal position on the amniotic fluid index.

OBJECTIVE: We investigated the influence of maternal positioning on the measurement of the amniotic fluid index (AFI) in third-trimester pregnancies. We wanted to determine whether a change in the position of the women, from supine-flat to supine-elevated, would influence the measurement of the AFI. METHODS: Each patient had AFI measurements obtained in both positions by the same investigator. RESULTS: We determined the values of the amniotic fluid index to be consistent in both positions for pregnancies with normal AFI measurements. CONCLUSIONS: Measurements of the amniotic fluid did not appear to be influenced by maternal position in the third trimester when the AFI was in the normal range.     

Prostate-specific antigen in amniotic fluid of normal and abnormal pregnancies

Objective: To examine if prostate-specific antigen (PSA) is present in amniotic fluid or maternal serum during pregnancy and if its presence is associated with fetal abnormalities.

Methods: Samples tested included amniotic fluids from 853 pregnant women for whom amniocentesis was performed; 312 nonpregnant women who donated blood; 259 pregnant women who donated blood at various gestational ages. Amniotic fluid or serum PSA was measured with an ultrasensitive time-resolved immunofluorometric procedure. 372 pregnancies were studied for the presence of genotypic or phenotypic fetal abnormalities.

Results: PSA was present in most amniotic fluids; the median PSA concentration increased from gestational week 11 to 22 and stabilized thereafter until delivery. The most prominent PSA concentration change occurred during gestational weeks 13–14. Pregnant women had significantly higher serum PSA concentrations than nonpregnant women; the pattern of serum fSA concentration change during pregnancy was similar to that of amniotic fluid; however, serum PSA concentrations were lower by a factor of 20–40. No association existed between amniotic fluid F'SA and maternal age, gender of fetus, or length of abstinence of mother from sexual intercourse. After gestational week 15, fetuses with trisomy 21 or 18, anencephaly, or renal disorders were associated with low amniotic fluid PSA levels.

Conclusion: Our data suggest that PSA may play a role in fetal development, especially at gestational ages between 13–20 weeks. The diagnostic usefulness of PSA in identifying fetal abnormalities remains to be determined.     

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。     

Development of individual growth standards for estimated fetal weight: II. Weight prediction during the third trimester and at birth

Using a weight estimation procedure based of the Rossavik growth model, we have evaluated the possibility of establishing individual growth curve standards for fetal weight estimates and of predicting birth weights in the second trimester. In 20 normal fetuses delivered at term, 95% of the weight estimates obtained after 26 weeks' menstrual age (MA) were within +/- 22% of the predicted weight estimates. In these same fetuses the mean difference between birth weight estimates based on growth patterns before 26 weeks, MA, and actual birth weights was 1.2%, with 95% of the percent deviations being between 13.3% and - 8.8%. In a similar prospective study, the mean percent difference was -1.7%, with a range of 9.6% to -13.6%. Direct comparison of weight estimates obtained during the last week before delivery with birth weight projections indicated that birth weight estimates obtained 14 weeks before delivery had smaller systematic and random errors than those obtained within a week of delivery. These results indicate that individual growth curve standards for fetal weight estimates and the growth potential of individual fetuses can be determined from growth patterns in the second trimester.     

Is there a relationship between fetal weight and amniotic fluid index?

OBJECTIVE: To establish whether there is a relationship between the amniotic fluid index and estimated fetal weight in the third trimester. The presence of a relationship would require adjustment of amniotic fluid index to take account of estimated fetal weight with potential improvement in its prediction of adverse perinatal outcomes. METHODS: Paired measurements of amniotic fluid index and estimated fetal weight from 274 low-risk pregnancies enrolled in a longitudinal study of fetal growth. Measurements were made at fortnightly intervals from 30 weeks' gestation until delivery. A relationship between amniotic fluid index and estimated fetal weight was sought at gestational age week intervals of 30-32, 33-35, 36-38 and 39-41. RESULTS: One thousand and three pairs of measurements of amniotic fluid index and estimated fetal weight were available for analysis. Mean amniotic fluid index decreased towards term as expected. There was no correlation between amniotic fluid index and estimated fetal weight. Furthermore, there was no correlation between amniotic fluid index and estimated fetal weight at any of the gestational age intervals. CONCLUSIONS: There is no clinically relevant correlation between amniotic fluid index and estimated fetal weight. It should remain clinical practice to take account of gestational age when interpreting amniotic fluid index but it is not necessary to make adjustments for estimated fetal weight.     

Caveats in the monitoring of fetal growth using ultrasound estimated fetal weight

IntroductionUltrasound estimated fetal weight is increasingly being used in the monitoring of fetal growth. Differences between estimated fetal weight formulae, curves and measurement methods could lead to significant differences in results. The aim of this study was to investigate the potential impact of these differences on estimated fetal weight and its use in monitoring fetal growth, both by modelling and by analysis of ultrasound scan data.MethodsFour estimated fetal weight curves were compared in their original form and also normalised to term weight. Estimated fetal weight was calculated from 50th centiles of widely used charts of abdominal and head circumference and femur length and plotted on a widely used estimated fetal weight curve. Fetal measurement data were used to assess the impact of fetal proportions on estimated fetal weight error and on growth trajectory when different estimated fetal weight formulae are used.ResultsEstimated fetal weight curves differ significantly, but after normalisation there is closer agreement. Estimated fetal weight modelled using modern measurement methods differs from the widely used estimated fetal weight growth curve. Errors in estimated fetal weight are correlated with differences in fetal proportions and this can lead to significant changes in estimated fetal weight growth trajectory if different estimated fetal weight formulae are used.ConclusionsChoice of measurement methods, estimated fetal weight formulae and growth curves have a significant effect on estimated fetal weight growth trajectories relative to normal ranges. It is important to understand these caveats when using estimated fetal weight to monitor fetal growth.     

Ultrasonographic estimation of fetal weight: acquiring accuracy in residency.

OBJECTIVE: Ultrasonographic imaging is considered an objective means for fetal weight estimation. The goals of this study were to determine the accuracy of ultrasonographic estimates of fetal'weight performed by residents in training and to ascertain how rapidly the residents gained proficiency in this regard. METHODS: A total of 300 ultrasonographic estimates of fetal weight and corresponding birth weight were collected and stratified into 4 groups by the level of residents' experience, from level 1 (inexperienced, with <6 months of exposure) to level 4 (advanced experience, with at least 24 months of training). The proportional difference between ultrasonographic estimates of fetal weight and birth weight was calculated for each case and grouped according to the level of training of the examiner. The derived data were compared by analysis of variance, linear regression, and chi2 test. RESULTS: Significant increases in the accuracy of ultrasonographic estimates of fetal weight were observed with advancing levels of resident experience (P< .0001). Overall, 30.6% of ultrasonographic estimates of fetal weight fell within 5% of birth weight, and 60.6% fell within 10%. Among the least experienced residents (<6 months of training), 49.4% of estimates fell within 10% of birth weight; among those with 6 to 11 months of experience, 53.5% of estimates fell within 10%; among those with 12 to 23 months of experience, 64.1 % of estimates fell within 10%; and among the most experienced (>24 months), 73.6% of estimates fell within 10%. CONCLUSIONS: There is a learning curve for ultrasonographic estimates of fetal weight, with a significant decrease in the percent error seen with advancing training among residents, reaching acceptable levels of more than 70% of estimates within 10% of birth weight after 24 months of ultrasonographic experience.     

Maternal serums and amniotic fluid levels of human placental lactogen in gestational diabetes.

Human placental lactogen (hPL) levels were measured radioimmunologically in maternal serum and in amniotic fluid between the 37th and 39th weeks of gestation in sixteen gestational diabetic and thirty normal pregnant women. There was no significant difference in maternal serum hPL levels between diabetic (6.1 microgram/ml) and normal pregnant women (6.4 microgram/ml). In contrast, the diabetic group was found to have significantly (P less than 0.001) higher concentrations of amniotic fluid hPL (1.2 microgram/ml) than normal pregnant women (0.8 microgram/ml).     

Delivery room care of newborns with meconium-stained amniotic fluid

Over the past two decades, airway management guidelines for infants born through meconium-stained amniotic fluid (MSAF) have moved towards a less invasive approach. Previously, infants born through MSAF received immediate intubation and endotracheal suctioning. That airway suctioning intervention was believed to decrease the negative side effects that came secondary to the presence of MSAF. Current guidelines do not recommend any routine suctioning for vigorous or non-vigorous infants born through clear or meconium-stained fluid. This review explores the evidence behind the new recommendations regarding infants born through MSAF and the implications the updated guidelines have on current nursing practice and future research.     

羊水细胞培养技术的临床应用

目的探索羊水细胞染色体培养改良方法,提高培养、收获成功率,满足临床诊断需要。方法对493例羊水标本进行细胞培养和染色体收获,并对实验细节进行优化,建立标准操作程序。结果羊水培养成功率99.8%（492/493）,发现21-三体6例、18-三体2例、其他异常2例。结论采取严格质量控制;保留换液后的上清,解决因收获失败无法诊断的问题;采取肝素抗凝等,消除母血细胞干扰,可使羊水细胞培养成功。     

Effect of amniotic fluid volume on ultrasonic fetal weight estimation.

We evaluated the relationship between the amniotic fluid index and the accuracy of fetal weight estimation using ultrasonography. Six hundred and sixty-four patients, between 20 and 42 weeks' gestational age, who were delivered within 1 week of a sonographic examination were studied. Five formulas for estimating fetal weight also were studied. Systematic and random errors in predicting birth weight were analyzed relative to birth weight and amniotic fluid index. The accuracy of sonographic fetal weight estimation was independent of amniotic fluid index across all gestational ages and birth weights. Each of the five formulas had similar error percentages, and no significant differences were detected. Predicted fetal weight was significantly underestimated with each of the formulas studied, a finding that was also independent of birth weight and amniotic fluid index. We conclude that ultrasonography can be used reliably to estimate fetal weight in patients with altered amniotic fluid volumes.