Evaluation Of Amniotic Fluid Volume Research Articles

Ultrasound evaluation of normal rhesus macaque fetal biometry and uteroplacental hemodynamics.

Nonhuman primates are important preclinical models for translational, reproductive, and developmental science. Clinical evaluation of human fetal development is performed using standard sonographic-derived fetal biometry, assessments of amniotic fluid, and uteroplacental hemodynamics. These noninvasive in utero measurements provide important information regarding fetal growth and pregnancy well-being. Abnormalities in fetal growth, amniotic fluid volume, or placental vascular function are associated with placental insufficiency and adverse perinatal outcomes including stillbirth. The fetal biometric parameters most commonly assessed are biparietal diameter, head circumference, abdominal circumference, and femur diaphysis length. Evaluation of amniotic fluid volume includes measuring the fluid in four quadrants of the uterus to generate an Amniotic Fluid Index. Measures of uteroplacental hemodynamics typically include doppler assessment of the umbilical artery and ductus venosus, but can also include interrogation of the uterine artery and umbilical vein. In this study, we compile prenatal ultrasound data of fetal biometry, amniotic fluid measurements, and uteroplacental hemodynamics obtained from pregnancy studies conducted at the Oregon National Primate Research Center. The data included are from control unperturbed pregnant animals who have not undergone in utero experimental manipulations. This is the first report of comprehensive sonographic measurements following standardized clinical obstetric protocols utilized in rhesus macaques. The outcome is a large, prenatal ultrasound resource to be used by laboratory animal researchers in future nonhuman primate pregnancy studies for antenatal assessment.

The relationship between amniotic fluid index and accuracy of sonographic estimated fetal weight

Background: Ultrasound is the gold standard in evaluation of amniotic fluid volume and diagnosis of volume disorders as oligohydramnios and polyhydramnios. While the amniotic fluid may be thought of as an expansion of the foetus extracellular fluid compartment during the first two trimesters of pregnancy, most amniotic fluid is actually produced during the third trimester due to foetal micturition. We hypothesised a link between the amniotic fluid indexes (AFI) and estimated foetal weight (EFW), which might suggest that EFW be considered in amniotic fluid evaluation.Methods: This cross-sectional study was conducted on 75 pregnant cases (Age was >18 years) and carrying singleton pregnancy with GA from 18 weeks to 40 weeks (GA evaluation was based on menstrual history & early US assessment) for 1 year. All participants underwent full history taking, abdominal ultrasonography examination and assessment of amniotic fluid index.Results: The majority of included pregnancies showed cephalic presentation of the fetus. The overall AFI ranged from 2 to 30 cm, with a mean value of 17.2 (SD, 7.4) cm and a median value of 18 (IQR, 11) cm. The majority of included pregnancies showed a normal BPP. There was no significant association between AFI and EFW for all categories of gestational age, except in the 27 29 week’s group.Conclusions: The AFI and EFW numbers found in this research fell within a certain range. Nevertheless, these variables showed no statistically meaningful correlation with one another. Inferring from that, it seems unlikely that either measure is worth focusing on when the other is subject to fluctuation.

AIUM-ACR-ACOG-SMFM-SRU Practice Parameter for the Performance of Standard Diagnostic Obstetric Ultrasound Examinations.

AIUM-ACR-ACOG-SMFM-SRU Practice Parameter for the Performance of Standard Diagnostic Obstetric Ultrasound Examinations.

Evaluation of Amniotic Fluid Volume among Sudanese Diabetic Patients in Third Trimester Using Ultrasound

Assessment of amniotic fluid volume in diabetic pregnancies is important for maternal and fetus health judgment and pregnancy outcome and for this reason the purpose of this study is relevant using two ultrasonographic methods. The study included 49 Sudanese pregnant women with diabetes mellitus and 20 subjects as control group .The study was conducted at Omdurman Military hospital and Al -Saudi hospital in the period from December 2011 to April 2012. Ultrasound was done by using Mindray 6600, 2200 ultrasound machine fitted with 3.5 MHZ convex probe. Amniotic fluid volume (AFV) was measured by largest pocket and Amniotic fluid index (AFI) .The mean AFI for control group was found to be (16.6±2.4) and the largest pocket was (6.6±0.7),for diabetic sample AFI was (20.3±5.6), largest pocket was (7.4±1.9).T-test showed that AFI was found to be 4.66 at p <0.001, largest pocket was 2.93 at p-value 0.005. There is significant difference between AFI measurements and largest pocket for diabetic pregnant ladies compared to the control group.Measurements of AFV using ultrasound compared with type of diabetic and diabetic status is of great value to categorize the relative risk of complications related to diabetes.

Prise en charge du dépassement de terme

The classic pregnancy term is between 37 and 42 weeks of gestation and the perinatal mortality and morbidity rates increasing progressively during this period, it is difficult to decide of an "ideal" term above which a medical intervention (induction of labour) brings more benefits than risks linked to the natural evolution of pregnancy. There is a good scientific evidence for the induction of labour from 41 weeks of gestation, defined like "postdating" term, when the cervical conditions are favourable (Bishop score>5) and systematically from 42 weeks (significative reduction of perinatal mortality rate and not increased rate of cesarean delivery compared with expectant management). An intensive antenatal surveillance involving a nonstress test and an evaluation of amniotic fluid volume is an efficient alternative when the conditions of delivery are unfavourable between 41 and 42 weeks of gestation or when the woman does not wish induction.

Sonographic evaluation of amniotic fluid volume.

Sonographic evaluation of amniotic fluid volume.

Sonographic assessment of amniotic fluid volume between 11 and 24 weeks of gestation: construction of reference intervals related to gestational age.

At present, most of the methods for sonographic assessment of amniotic fluid volume are unreliable in the second trimester of pregnancy, or else they do not present nomograms related to gestational age. The aim of this prospective cross-sectional study was to construct normal reference ranges of four ultrasound parameters for the evaluation of amniotic fluid volume which could be applied in the second trimester. For these parameters we calculated normal curve limits suitable for use in clinical practice. From a population of normal pregnant women between the 12th and the 24th weeks of gestation undergoing a routine ultrasound examination during 1997 at our institute, 273 were found to be suitable for the study, after the exclusion of all cases which presented any feto-maternal pathology or complications up to the 24th week. The largest 'amniotic pocket' in a vertical direction, free of small fetal parts and umbilical cord, was measured: the maximum vertical and transverse diameters were measured on the same scan; the mean diameter and the product of the two diameters were calculated. The 'mean amniotic fluid diameter', the 'two-diameter pocket', the 'largest vertical pocket' and the 'largest transverse pocket' were the four sonographic parameters considered. The four parameters correlated well with gestational week and with the biparietal diameter; the normal reference intervals and normal curve were then calculated. All these parameters were found to have good intra- and interoperative reproducibility. We conclude that the use of an ultrasound semiquantitative method based on the measurement of a single amniotic fluid pocket and involving normal reference intervals according to gestational age could improve the early diagnosis of amniotic fluid variations during the second trimester, although this has yet to be confirmed by extensive clinical trials.

Subjective versus objective evaluation of amniotic fluid volume of pregnancies of less than 24 weeks' gestation: how can we be accurate?

This study was undertaken to compare subjective versus objective ultrasonic evaluation of amniotic fluid volume in pregnancies of less than 24 weeks' gestation. Amniotic fluid volume was subjectively (visualization without ultrasonic measurements) and objectively (visual interpretation with ultrasonic measurements) evaluated in 42 singleton pregnancies undergoing termination. The actual amniotic fluid volume was then determined using a dye-dilution technique. The women evaluated were in their mid-20s, primarily African American, and between 15 and 23 weeks' gestation. There was no significant difference in the total number of correct estimates of amniotic fluid volume when the data were stratified by level of operator experience (P = .34), ultrasonic technique (P = .33), or the combined correct subjective versus combined correct objective estimates (P = .68). We have concluded that the accuracy of amniotic fluid volume assessment in pregnancies of less than 24 weeks is not influenced by the level of operator experience or the type of ultrasonic measurement.

The accuracy of ultrasound evaluation of amniotic fluid volume in singleton pregnancies: The effect of operator experience and ultrasound interpretative technique

The objective of this study was to evaluate the effect of operator experience and ultrasound interpretation technique on the accuracy of ultrasound estimates of amniotic fluid volume. Ultrasound evaluation was carried out by an obstetric resident, a nurse sonographer, a maternal-fetal medicine fellow, and a maternal-fetal medicine staff member to subjectively estimate (visual interpretation without sonographic measurements) amniotic fluid volume in 63 pregnancies. Amniotic fluid volume was also evaluated using ultrasound measurements based on the largest vertical pocket technique, the amniotic fluid index, and the two-diameter pocket method. The accuracy of these ultrasound estimates was assessed by comparing the ultrasound results to actual amniotic fluid volume as determined by a dye-dilution technique. For analysis, amniotic fluid volumes were classified as oligohydramnios, normal, or hydramnios using established volumetric criteria for singleton pregnancies. Subjective estimates ranged from 65% to 70% correct and did not differ by operator experience except for the more accurate diagnosis of hydramnios by the maternal-fetal medicine staff. The three sonographic measurements were similar in overall accuracy (59–67%). The two-diameter pocket method was, however, significantly more accurate in identifying oligohydramnios. It appears that neither operator experience nor sonographic technique greatly affects the accuracy of ultrasound estimates of amniotic fluid volume. © 1997 John Wiley & Sons, Inc. J Clin Ultrasound 25:249–253, 1997

The accuracy of ultrasound evaluation of amniotic fluid volume in singleton pregnancies: The effect of operator experience versus sonographic measurements

The accuracy of ultrasound evaluation of amniotic fluid volume in singleton pregnancies: The effect of operator experience versus sonographic measurements

Amniotic fluid volume: Fluid dynamics and measurement technique

Evaluation of amniotic fluid volume is an important aspect of obstetrical ultrasound. Several methods are currently used to describe amniotic fluid volumes. The most common are the subjective assessment of fluid and the semiquantitative methods. The reproducibility of these methods is excellent in experienced hands. Because of the multiple methods used to assess fluid, both oligohydramnios and polyhydramnios have numerous definitions. Regardless of which definition is used, it is clear that both of these entities are associated with a variety of fetal and maternal conditions. Abnormal amniotic fluid volume may be the only or earliest sonographic sign of an obstetrical problem. Therefore, it is important that sonologists are familiar with amniotic fluid volume assessment. Although subjective and semiquantitative techniques may produce similar results, a numerical scale is no substitute for experience and training. One should be able to recognize lesser degrees of fluid abnormality and be able to assess the trend of amniotic fluid volume in serial examinations.

Correlation of subjective assessment of amniotic fluid with amniotic fluid index

We assessed the correlation between abnormal amniotic fluid volumes as defined by the two techniques of (1) subjective evaluation and (2) the amniotic fluid index. Ultrasound evaluation of amniotic fluid volume was conducted on 420 pregnant women with known gestational age greater than twenty weeks but less than 42 weeks. Amniotic fluid was evaluated subjectively and placed into one of three categories: normal, oligohydramnios or polyhydramnios. After fetal biometry was performed, the amniotic fluid volume was assessed semi-quantitatively by the amniotic fluid index technique and assigned to similar categories. We analyzed the data with 2 × 2 contingency tables, using amniotic fluid index as the ‘gold standard test’. Our study demonstrates that there was moderate agreement (κ.5) between both amniotic fluid techniques in the identification of oligohydramnios. However, agreement between the techniques was poor for the identification of polyhydramnios (κ.16).

Superiority of the four-quadrant sum over the single-deepest-pocket technique in ultrasonographic identification of abnormal amniotic fluid volumes

Ultrasonographic estimation of amniotic fluid volume is an important adjunct to assessment of fetal well-being. However, no single method has emerged as most predictive. Many ultrasonographers use subjective or single-pocket guidelines in evaluation of amniotic fluid volume. We therefore assessed the ability of a maximum-vertical-pocket technique to identify patients with abnormal volumes of amniotic fluid. A total of 1168 patients was studied. Oligohydramnios (n = 76) was defined as an amniotic fluid index <5th percentile for gestational age (70 to 98 mm). Hydramnios (n = 51) was defined when the amniotic fluid index was >95th percentile (185 to 249 mm). The ability of the maximum-vertical-pocket technique to identify cases with oligohydramnios by amniotic fluid index was poor: sensitivity was 42% and positive predictive value was 51%. Fifty-eight percent of cases with oligohydramnios by amniotic fluid index had "normal" values according to the single-pocket technique. The correlation coefficient between amniotic fluid index and maximum vertical pocket was 0.51, R2 = 24%. The correlation between the maximum vertical pocket and amniotic fluid index was somewhat better in cases of polyhydramnios (r = 0.79, R2 = 62%), but the sensitivity, positive predictive value, and false-negative rates were high as in oligohydramnios. These data suggest that the maximum-vertical-pocket technique has adequate specificity but is a poor screening tool. The results demonstrate that use of gestation-specific norms for the amniotic fluid index identifies abnormal amniotic fluid volumes more efficiently than the single-pocket technique.

Postdate fetal surveillance: Is 41 weeks too early?

During an 18-month period, 293 patients had a nonstress test and ultrasonographic evaluation of amniotic fluid volume twice weekly beginning at 41 weeks' gestation. Patients were admitted for induction of labor for either an abnormal nonstress test result or oligohydramnios. A control population consisted of 59 low-risk patients who were delivered between 39 and 41 weeks' gestation and had antepartum testing within 4 days of delivery. Study patients who were delivered between 41 and 42 weeks' gestation had a significantly increased incidence of abnormal nonstress tests, oligohydramnios, cesarean sections for fetal distress, and admissions to the neonatal intensive care unit compared with control patients. The abnormal fetal testing and adverse perinatal outcome associated with pregnancies over 42 weeks were also found in pregnancies between 41 and 42 weeks' gestation. These data support the concept that postdate fetal testing should begin at 41 weeks of gestation.

Acute Oligohydramnios in postdate pregnancy

The evaluation of amniotic fluid volume plays a major role in antepartum fetal surveillance. Although the definition of diminished amniotic fluid volume varies, this sign is considered by itself an indication for intervention in the near-term fetus. The interval of testing is predicated on the concept that amniotic fluid volume diminishes slowly (unquantified) as a result of developing hypoxia. We present six postterm pregnancies in which amniotic fluid volume diminished abruptly over 24 hours. Although one fetus died, the three babies delivered by cesarean section and the two babies delivered after a 2-day labor did well, despite obvious postmaturity syndrome, meconium staining, and variable decelerations. Apgar scores in the survivors were above 8, and pH results failed to confirm hypoxia. These data suggest the need to better understand the mechanisms regulating amniotic fluid volume.

Limitations of using maximum vertical pocket and other sonographic evaluations of amniotic fluid volume to predict fetal growth: Technical or physiologic?

Maximum vertical pocket measurement and subjective sonographic impression of amniotic fluid volume were studied in 487 selected pregnancies. Opiate abuse, suspected fetal growth retardation, and suspected postterm gestation were negatively correlated with maximum vertical pocket; suspected fetal growth acceleration and increasing birth weight were positively correlated. Maximum vertical pocket appeared to peak at 31 to 33 weeks (p < 0.05), and was related to fetal growth (p < 0.001). Subjective sonographic evaluation of amniotic fluid volume yielded comparable results. Unfortunately, neither technique could be used to accurately predict the birth of a small, appropriate, or large for gestational age infant in the individual pregnancy. Abnormal fetal growth could be reliably excluded in only a small number of cases. This and previous studies suggest that diagnosis of abnormal fetal growth by means of sonographic amniotic fluid volume evaluation could be limited by physiologic variation rather than technical error in measurement.

Ultrasound evaluation of amniotic fluid volume: II. The relationship of increased amniotic fluid volume to perinatal outcome

Qualitative amniotic fluid volume determination is a routine part of fetal biophysical profile score testing. The relationship between polyhydramnios and poor perinatal outcome has been previously documented. We have undertaken a retrospective chart review which relates qualitative amniotic fluid volume as determined at the time of last biophysical profile score assessment to perinatal outcome in 7562 referred high-risk obstetric patients. Gross and corrected perinatal mortality in association with normal qualitative amniotic fluid volume ranged from 4.65/1000 and 1.97/1000, respectively, to 32.9/1000 and 4.12/1000 in association with increased qualitative amniotic fluid volume, respectively. The incidences of major congenital anomaly and fetal macrosomia were significantly related to qualitative amniotic fluid volume.

Ultrasound evaluation of amniotic fluid volume: I. The relationship of marginal and decreased amniotic fluid volumes to perinatal outcome

Qualitative amniotic fluid volume determination is a routine part of fetal biophysical profile score testing. The relationship between oligohydramnios and poor perinatal outcome has been previously documented. We have undertaken a retrospective chart review relating qualitative amniotic fluid volume as determined at the time of last biophysical profile score assessment to perinatal outcome in 7582 referred high-risk obstetric patients. Gross and corrected perinatal mortality in association with normal qualitative amniotic fluid volume ranged from 4.65/1000 and 1.97/1000, respectively, to 187.5/1000 and 109.4/1000 in association with decreased qualitative amniotic fluid volume, respectively. The incidences of major congenital anomaly and intrauterine growth retardation were significantly related to qualitative amniotic fluid volume.

Comparison of antepartum testing schemes for the management of the postdate pregnancy

We analyzed the outcome results of 583 postdate pregnancies managed prospectively by one of three antepartum testing schemes, each predicated on the nonstress test. In scheme 1, we relied upon the contraction stress test for evaluation of the nonreactive nonstress test. In scheme 2, we used a modified biophysical profile to evaluate the nonreactive nonstress test. In addition, patients were tested semiweekly. In scheme 3, we added routine weekly ultrasound evaluation of amniotic fluid volume to scheme 2. Only in scheme 3 did we induce labor for decreased amniotic fluid volume or fetal cardiac decelerations irrespective of reactivity. The incidence of fetal distress, perinatal mortality, and perinatal morbidity was increased in babies with decelerations or decreased amniotic fluid volume. Nevertheless, outcome results in scheme 2 were improved over those with scheme 1 and were best with scheme 3. These results suggest a benefit to both semiweekly testing and liberalized criteria for intervention in postdate pregnancies. We also compared the outcome results of scheme 3 with those reported for schemes in which the weekly contraction stress test was used as the primary form of surveillance. We found the outcome results comparable in that both schemes showed minimal mortality and morbidity statistics but high intervention rates (25% to 30%). Differences in methodology and test criteria, however, make such comparisons less than ideal.