Updating the amniotic fluid index nomograms according to perinatal outcome.

Background: The two most commonly used nomograms for amniotic fluid index (AFI) were developed by Moore and Cayle and Magann et al. However, there are several inconsistencies between the two methods.Objective: The aim of the study was to determine whether these differences carry clinical significance.Methods: A retrospective cohort of women with singleton pregnancies evaluated for AFI during pregnancy at a tertiary medical center in 2007-2014 were divided into five groups: group A, definite oligohydramnios-AFI below the fifth percentile according to the nomograms of both Moore and Cayle and Magann et al.; group B, intermediate oligohydramnios-AFI below the fifth percentile according to only one nomogram (Moore and Cayle); group C, euhydramnios-normal AFI according to both nomograms; group D, intermediate polyhydramnios-AFI above the 95th percentile according to one nomogram (Magann et al.); group E, definite polyhydramnios-above the 95th percentile according to both nomograms. The association of group by maternal and perinatal outcomes was analyzed.Results: A total of 6987 women were included: group A, 996 (14%); group B, 1344 (19%); group C, 2561 (37%); group D, 1051 (15%); group E, 1034 (15%). Group B (intermediate oligohydramnios) was characterized by significantly lower rates of adverse perinatal outcomes than group A (definite oligohydramnios): small for gestational age neonate (12.3 versus 15.2%, p = .05), neonatal intensive care unit admission (11.1 versus 21.5%; p < .001), composite respiratory outcome (4.8 versus 9.8%; p < .001), and neonatal sepsis (6.4 versus 10.8%; p < .001). No such differences were found between groups B and C. Group D (intermediate polyhydramnios) differed from group E (definite polyhydramnios) by lower rates of 5 minutes Apgar score <7 (1.3 versus 3.2%; p = .003), neonatal intensive care unit admission (10.9 versus 14.4%; p = .02), and major congenital anomalies (1.7 versus 5.6%; p = .02). There was no difference in these parameters between groups D and C.Conclusion: This study suggests that intermediate oligohydramnios and intermediate polyhydramnios are not associated with adverse perinatal outcomes. Outcome in these pregnancies is similar to pregnancies with euhydramnios. Commonly used AFI nomograms should be updated.

Serial assessment of amniotic fluid index in uncomplicated term pregnancies: prognostic value of amniotic fluid reduction.

OBJECTIVE: Assessment of amniotic fluid volume in association with a non-stress test is a commonly used method to monitor fetal well-being in high-risk pregnancies. The aims of our study were to determine whether oligohydramnios and the trend in amniotic fluid volume have prognostic significance in low-risk pregnancies between 40.0 and 41.6 weeks' gestation. METHODS: Between January 1997 and December 2000, all uncomplicated gestations with a singleton non-anomalous fetus reaching 40.0 weeks' gestation underwent semi-weekly monitoring of amniotic fluid index (AFI) until delivery. Oligohydramnios was defined as an AFI of < or = 5 cm. Changes in AFI were expressed as centimeters per day, and were calculated as: [(last AFI before delivery minus first AFI at 40.0 weeks) / interval in days between the two scans]. Adverse outcome was considered the occurrence of 5-min Apgar score < 7; umbilical artery pH < 7.0; Cesarean section for fetal distress; or fetal death. Comparisons between the groups with favorable and adverse outcomes was performed with chi(2) or Fisher's exact test for categorical variables, and Student's t test for continuous variables. A two-tailed p value < 0.05 was considered significant. RESULTS: A total of 3050 women met the study criteria, and underwent a median number of two (range 1-7) sonographic assessments of AFI after 40.0 weeks, with oligohydramnios detected in 341 women. In 1466 women at least two serial AFI determinations were obtained, allowing computation of an AFI trend. Gestations resulting in adverse perinatal outcome (n = 167, 5.5%) had a significantly higher rate of oligohydramnios (33/167, 19.8% vs. 308/2883, 10.7%, p = 0.001), but a similar rate of reduction in AFI ( -0.65 +/- 0.64 vs. - 0.66 +/- 0.66 cm/day; p = 0.85) than those with favorable outcome. The difference in rate of reduction of AFI between the two groups was not significant, even in the subset of gestations that developed oligohydramnios ( -1.08 +/- 0.87 vs. -1.26 +/- 0.89 cm/day; p = 0.27). CONCLUSION: A sonographic diagnosis of oligohydramnios carries an increased risk of adverse perinatal outcome, even in low-risk pregnancies after 40 weeks. The trend in amniotic fluid volume reduction does not seem to have prognostic significance.

Amniotic fluid index in normal pregnancy: an assessment of gestation specific reference values among Indian women.

AIM: To obtain a gestational reference range for the amniotic fluid index (AFI) among Indian women. METHODS: An analysis of AFI estimations was undertaken in 517 Indian women with normal pregnancy between 16 and 42 weeks of gestation. It was a prospective, cross-sectional study conducted in a university teaching hospital. Women with fetal anomalies, pregnancy-induced hypertension, diabetes mellitus, and other maternal complications were excluded from the study. The median, the 5th and the 95th percentile values were calculated for each gestational week and these values were compared with other studies. RESULTS: The median reached its peak at the 27th week of gestation. We observed approximately 6 cm as the lower limit of normal (5th percentile) and approximately 18 cm (95th percentile) as upper limit of normal AFI at term for our population, whereas in the Caucasian population, the values were approximately 7 cm and approximately 20 cm, respectively. All gestation specific AFI values were lower in the studied population of Indian women compared with other studies on Caucasian population (P < 0.01 for 5th percentile & P < 3.26 x 10(-7) for 95th percentile), but slightly higher than the Chinese population. CONCLUSION: Amniotic fluid index values differ in different populations. We standardized the reference values for normal AFI in Indian women. We found that they are lower in the population studied compared with reported values in the Caucasian population, but slightly higher than the Chinese population.

Clinical assessment of amniotic fluid.

Amniotic fluid volume estimation has become an integral part of fetal evaluation. Although the sonographic techniques clinically available are limited in their accuracy and predictive value, the careful performance of AFI measurements provide important and complementary clinical data on which to base management decisions in pregnancies at risk.

Amniotic fluid assessment. Methods and role in fetal assessment.

AFV assessment by one method or another has become an adjunct to nonstress testing in most pregnancies requiring surveillance. Evaluation by nonstress test and amniotic fluid assessment for fetuses with maternal risk factors in a protocol such as that outlined by Devoe is common practice. Adaptation of that algorithm (Fig. 4) to the needs of the clinical setting are simple. Quantitative and nonquantitative methods show an increase in perinatal morbidity and mortality with abnormal values. Those trends are most evident in studies involving postdate gestations, such as those by Marks and Lagrew. The literature and its applied lessons for clinical practice are confused by the many variables considered by those investigating AFV assessment. Superiority of one method over another has not been demonstrated consistently from one study to the next. The good correlation in AFV estimated by ultrasonography and determined by dye-dilution techniques is still based on limited studies that are unlikely to be replicated soon because of the invasive nature of the test. Even in the best circumstances, errors at extremes of AFV are common with the use of ultrasonography. At present, the best recommendations from the literature seem to take two main directions. Antenatal testing of the fetus at risk should include some evaluation of AFV. The fetus with apparently abnormal AFV should be studied anatomically and considered for delivery if decreased AFV is associated with other test abnormalities--i.e., a nonreactive nonstress test.

Subjective ultrasonographic assessment of amniotic fluid depth: comparison with the amniotic fluid index.

The purpose of this study was to evaluate the ability to identify abnormalities in amniotic fluid volume by subjective ultrasonographic assessment compared to a semiobjective method. In 886 consecutive ultrasound examinations subjective assessment of the amniotic fluid volume was performed and graded into 3 categories: normal, decreased, and increased. Following that, a four-quadrant sum (amniotic fluid index) was performed by the same experienced ultrasonographer and divided into 3 categories using the 5th and 95th percentiles. The sensitivity of the subjective analysis to diagnose a decreased amniotic fluid volume when compared with the amniotic fluid index was 58% (95% confidence interval, CI: 40-70%), with a false-positive rate of 17% (CI 8-32%). The sensitivity of the subjective analysis to diagnose an increased amniotic fluid volume when compared with the amniotic fluid index was 100% (CI 70-100%). However, the false-positive rate was 74% (CI 55-85%). Diagnosis of a normal amount of amniotic fluid by the subjective technique had a sensitivity of 96% (CI 95-97%) and a false-positive rate of 3% (CI 2-4%). Subjective ultrasonographic assessment of the amniotic fluid volume may serve as a screening test for the experienced ultrasonographer. However, when a decreased or increased amount of amniotic fluid volume is suspected, one may elect to use the amniotic fluid index for confirmation of the subjective impression.

Amniotic fluid volume assessment: comparison of ultrasonographic estimates versus direct measurements with a dye-dilution technique in human pregnancy.

OBJECTIVE: The purpose of our study was to compare the accuracy of clinical ultrasonographic techniques of amniotic fluid volume assessment with a dye-dilution technique. STUDY DESIGN: We compared amniotic fluid volume as measured by ultrasonographic techniques with a dye-dilution method in 50 women undergoing amniocentesis during the third trimester. Thirteen separate ultrasonographic techniques, including the amniotic fluid index, were evaluated with regression analysis. RESULTS: Amniotic fluid volumes as determined by dye-dilution ranged between 129 and 4444 ml. The amniotic fluid index overestimated the actual volume by as much as 88.7% at lower volumes and underestimated the actual volume by as much as 53.9% at higher volumes. CONCLUSIONS: Differences in measurement error between the other ultrasonographic methods and the amniotic fluid index did not appear to be sufficient to warrant changes in current clinical practice. A major source of error in ultrasonographic amniotic fluid volume assessment is that one-dimensional measurements are used to estimate the volume of a complex, three-dimensional object.

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 x 2 contingency tables, using amniotic fluid index as the 'gold standard test'. Our study demonstrates that there was moderate agreement (kappa.5) between both amniotic fluid techniques in the identification of oligohydramnios. However, agreement between the techniques was poor for the identification of polyhydramnios (kappa.16).