Amniotic Fluid Volume Determination Research Articles

Amniotic fluid volume assessment at the present stage of development

Amniotic fluid not only provides conditions for normal growth and development of the fetus, but also prevents umbilical cord compression and infection of the uterine cavity due to the existing bacteriostatic effect. In addition, amniotic fluid volume varies in pathological conditions of the fetus and the uteroplacental complex, which can lead to irreversible consequences. The aim of this study was to analyze features of assessing amniotic fluid volume at the present stage of development. In this review article, we analyzed, systematized, and summarized data obtained by foreign and domestic authors from 1980 to 2017. Reliable determination of amniotic fluid volume will optimize the management of pregnant women threatened by risk of perinatal pathology.

Determination of amniotic fluid volume in twin pregnancies: Ultrasonographic evaluation versus operator estimation

Objective: We sought to determine the accuracy of amniotic fluid volume estimation (visually) in diamniotic twin pregnancy versus ultrasonography techniques. Study Design: In this prospective study the volume of each sac in 23 sets of diamniotic twin pregnancies was subjectively and objectively estimated by a second-year obstetric resident, nurse sonographer, maternal-fetal medicine fellow, and maternal-fetal medicine staff. The actual volume was confirmed by amniocentesis and a dye-dilution technique. Results: There was no difference in the total number of correct estimates of volume by level of operator experience (P =.98), ultrasonography technique (P =.87), or combined subjective versus objective correct estimates (P =.87). Identification of low volume was not different among the four evaluators (P =.48), but the percentage of correct estimates was poor (7%-29%). The 2-diameter pocket was a better predictor of oligohydramnios (57%) than the amniotic fluid index or the largest vertical pocket (12.5%; P =.002). Conclusion: The extremes of volume (low or high) are poorly identified by the subjective or objective assessment of volume. (Am J Obstet Gynecol 2000;182:1606-9.)

Three-Dimensional Method for Determination of Amniotic Fluid Volume in Intrauterine Pockets

Background: Although current ultrasound techniques provide a linear (amniotic fluid index; AFI) or two-dimensional area index of amniotic fluid (AF), these indices have limited correlation with actual AF volume. We sought to quantify the three-dimensional volume of ultrasound-identified AF pockets, as assessed by the AFI and two-dimensional area methods. The BVI 2500 (Bladder Volume Instrument 2500; Diagnostic Ultrasound Corp., Redmond, WA) has been used to quantify the volume of residual urine in the bladder.Instrument and Method: The BVI 2500 (Diagnostic Ultrasound Corp.) ultrasound uses a rotating 2-MHz transducer, computer-defined fluid interface, and computer integration of 12 cross-sectional images to calculate three-dimensional fluid volume. After providing written informed consent, 14 term pregnant patients (36–42 weeks) were evaluated using the BVI 2500 and an Ultramark 8 sector scan (Advanced Technology Laboratory, Bothell, WA). The largest vertical fluid pocket in each quadrant of the abdomen was identified with the sector scan, and vertical and horizontal measurements for AFI and two-dimensional area were recorded. Simultaneous AF volume measurements of each pocket were performed three times with the bladder volume instrument, and maximum values were used. Three-dimensional volume, two-dimensional area, and AFI values were compared by correlation analysis, with P ≤ .05 considered statistically significant.Experience: Among all patients, the average (± standard deviation) AFI was 7.6 ± 4.1 (range 1.5–16.4) cm, and the average two-dimensional area was 30.9 ± 21.1 (range 4.3–81.3) cm2. This corresponded to an average three-dimensional volume of 215 ± 134 (range 23–497) cm3. Three-dimensional volume correlated highly with both AFI (r = 0.9; P < .001) and two-dimensional area (r = 0.86; P < .001). One AFI centimeter was equivalent to a volume of 30 cm3.Conclusion: There are highly significant linear correlations of three-dimensional amniotic fluid volumes with AFI and two-dimensional area. The four pockets used in AFI determination account for only 50% of total AF volume. Three-dimensional determinations may aid in clinical assessments of AF volume.

Ultrasonographic assessment of amniotic fluid does not reflect actual amniotic fluid volume

OBJECTIVE: Our objective was to compare the ability of two methods of amniotic fluid assessment (two-diameter amniotic fluid pocket versus the amniotic fluid index) to predict oligohydramnios (actual amniotic fluid volume <500 ml) or polyhydramnios (actual amniotic fluid volume >1500 ml). STUDY DESIGN: The amniotic fluid index and the two-diameter amniotic fluid pocket were assessed before amniocentesis and determination of amniotic fluid volume with the dye (aminohippurate sodium)–dilution technique. To assess the detection of either oligohydramnios or polyhydramnios, the areas under the receiver-operator characteristic curves (±SE) were estimated by the point-to-point trapezoidal method of integration. Prediction limits were calculated by regression analysis of amniotic fluid index or two-diameter amniotic fluid pocket versus actual amniotic fluid volume and determination of 95th percentile ranges for amniotic fluid volume. RESULTS: We studied 144 patients with a mean (±SD) gestational age of 31.7 ± 5.5 weeks; mean (±SD) amniotic flluid index and two-diameter amniotic fluid pocket were 12.6 ± 6.1 cm and 21.2 ± 18.4 cm 2, respectively. Mean (±SD) actual amniotic fluid volume was 722 ± 735 ml (range 101 to 4318 ml). The areas under the four receiver-operator characteristic curves were not significantly different from the nondiagnostic line ( p < 0.05). Regression slopes ( r values) for amniotic fluid index and two-diameter amniotic fluid pocket versus actual amniotic fluid volume were 0.34 and 0.23, respectively. Calculation of the prediction limit for 95% confidence that oligohydramnios is absent requires that the amniotic fluid index be 30 cm and the two-dimension amniotic fluid pocket be 90 cm 2 , both thresholds of which are currently considered to represent clinical polyhydramnios. CONCLUSIONS: Both amniotic fluid index and two-dimension amniotic fluid pocket appear to be inaccurate predictors of actual oligohydramnios or polyhydramnios when compared with dye-dilution calculations of actual amniotic fluid volume. (Am J Obstet Gynecol 1997;177:291-7.)

Amniotic Fluid Index: An Appropriate Predictor of Perinatal Outcome

Qualitative amniotic fluid volume determination is a routine part of the fetal biophysical profile score. Quantitative amniotic fluid volume measurement, however, is not a factor in the determination of the standard biophysical profile score. This study is a retrospective analysis of antepartum assessment of amniotic fluid volumes and their relationship to neonatal outcomes. The amniotic fluid index was calculated for all patients examined and perinatal outcome was studied for all patients assessed. Patients with reduced or increased amniotic fluid volume had a significant increase in meconium-stained amniotic fluid, Apgar scores less than 7 at 1 and 5 minutes, major congenital anomalies, admission to the neonatal intensive care unit, and were more likely to require delivery by cesarean section for fetal distress. This study suggests that a quantitative ultrasound measurement of amniotic fluid volume represents an effective discriminatory test to be used in pregnancy evaluation.

Identification of the small for gestational age fetus with the use of gestational age-independent indices of fetal growth

This study reviews the roles of sonographic assessment of the rate of growth of the fetal abdominal circumference, the femur length/abdominal circumference ratio, and qualitative determination of amniotic fluid volume as gestational age-independent indices for identification of the small for gestational age fetus. The sensitivity and specificity for single and combinations of test results were evaluated in 50 appropriate for gestational age and 40 small for gestational age fetuses. Positive and negative predictive values were derived for the general population. Our results indicate that either a rate of growth of the fetal abdominal circumference <- 10 mm/14 days or a femur length/abdominal circumference ratio ≥ 23.5 correctly identifies most small for gestational age fetuses. When the general population is screened, only 15% of small for gestational age fetuses will be missed by this combination of criteria. The presence of a pocket of amniotic fluid ≤2.0 cm is highly suggestive of a small for gestational age fetus. However, the presence of a pocket of amniotic fluid >2.0 cm does not guarantee an appropriate for gestational age fetus. We conclude that these gestational age-independent indices of fetal growth offer useful tools for differentiating between the small for gestational age and appropriate for gestational age fetus.

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.

Ultrasonographic determination of qualitative amniotic fluid volume in intrauterine growth retardation: Reassessment of the 1 cm rule

To assess the relative diagnostic efficacy of the “1 cm sign” for qualitative amniotic fluid volume determination in the prenatal evaluation of intrauterine growth retardation, 125 pregnancies resulting in small-for-gestational age infants were studied in a retrospective fashion. Qualitative amniotic fluid volume was designated as normal if at least one pocket of amniotic fluid measuring 1 cm in broadest diameter was identified. Of the 125 pregnancies with delivery of small-for-gestational age infants, only five would have been correctly predicted prenatally with qualitative amniotic fluid volume used as the sole criterion for intrauterine growth retardation. When this criterion was applied to a defined subset of 52 of these patients with last scans 0 to 15 days prior to delivery, only four cases would have been accurately predicted as having intrauterine growth retardation.

Qualitative Amniotic Fluid Volume Determination by Ultrasound

Qualitative Amniotic Fluid Volume Determination by Ultrasound

Qualitative amniotic fluid volume determination by ultrasound: Antepartum detection of intrauterine growth retardation

Qualitative amniotic fluid volume (AFV) was determined by a linear array ultrasound method in 120 patients referred with a diagnosis of intrauterine growth retardation (IUGR). Eighty-nine of these patients were delivered of a normal infant; the false positive rate by clinical methods alone was 74.2%. Qualitative AFV was termed normal if at least one pocket of amniotic fluid measuring 1 cm in its broadest diameter was identified. Qualitative AFV was normal in 91 patients, and 86 were delivered of a normal fetus (93.4%). In contrast, qualitative AFV was decreased in 29 patients, and 26 were delivered of a fetus with IUGR (89.9%). These differences were highly significant. Perinatal morbidity was increased tenfold in patients with decreased AFV. Overall, 26 of 31 IUGR fetuses (83.4%) demonstrated decreased qualitative AFV.