Objective:We sought to determine amniotic fluid (AF) volume in diamniotic twin gestations and to relate these findings to estimates using standard ultrasonic techniques.
Methods:In this prospective study, AF volume in 45 diamniotic twin gestations at 27-38 weeks was assessed by sonography using the largest vertical pocket technique, the AF index, and the two-diameter pocket method. After the three different sonographic estimations of AF volume, the true amount of AF was determined using amniocentesis and a dye-dilution technique.
Results:The individual sac AF volume was less than 500 mL in 35 amniotic cavities, 500-2000 mL in 48 sacs, and greater than 2000 mL in seven. Individual AF volume between 500 and 2000 mL was correctly predicted by sonographic use of the largest vertical pocket in 47 of 48 patients (98%), the AF index in 47 of 48 (98%), and the two-diameter pocket method in 39 of 48 (81%). Estimation of AF volume less than 500 mL was significantly more accurate using the two-diameter pocket method compared with either the AF index (P = .015) or the largest vertical pocket technique (P < .0001).
Conclusions:Currently available ultrasonic techniques to assess mid-range AF volume (500-2000 mL) in twin pregnancy are very accurate (81-98%). Oligohydramnios (less than 500 mL) is poorly identified by any sonographic method.
1. Chamberlain MB, Manning GA, Morrison I, Harman CR, Lange IR. Ultrasound evaluation of amniotic fluid. I. The relationship of marginal and decreased amniotic fluid volume to perinatal outcome. Am J Obstet Gynecol1984;150:245-249.
2.
2. Mercer LJ, Brown LG, Petres RE, Messer RH. A survey of pregnancies complicated by decreased amniotic fluid. Am J Obstet Gynecol1984;149:355-361.
3.
3. Chamberlain PF, Manning FA, Morrison L, Harman CR, Lange IR. Ultrasound evaluation of amniotic fluid. II. The relationship of increased amniotic fluid volume to perinatal outcome. Am J Obstet Gynecol1984;150:250-254.
4.
4. Hill LM, Breckle R, Wofgram KR, O'Brien PC. Oligohydramnios: Ultrasonically detected incidence and subsequent fetal outcome. Am J Obstet Gynecol1984;147:407-410.
5.
5. Hill LM, Breckle R, Thomas ML, et al. Polyhydramnios: Ultrasonically detected prevalence and neonatal outcome. Obstet Gynecol1987;69:21-25.
6.
6. Charles D, Jacoby HE. Preliminary data on the use of sodium aminohippurate to determine amniotic fluid volume. Am J Obstet Gynecol1966;95:266-269.
7.
7. Schiff E, Ben-Baruch G, Kushnir O, Mashiach S. Standardized measurement of amniotic fluid by volume correlation of sonography with dye dilutional technique. Obstet Gynecol1990;76:44-46.
8.
8. Phelan JP, Ohn MO, Smith CV, Rutherford SE, Anderson E. Amniotic fluid index measurements during pregnancy. J Reprod Med1987;32:601-604.
9.
9. Magann EF, Nolan TE, Hess LW, Martin RW, Whitworth NS, Morrison JC. Measurement of amniotic fluid volume: Accuracy of ultrasonography techniques. Am J Obstet Gynecol1992;167:1533-1537.
10.
10. Chervenak FA, Youcha S, Johnson RE, et al. Twin gestation: Antenatal diagnosis and perinatal outcome in 385 consecutive pregnancies. J Reprod Med1984;29:727-730.
11.
11. Beck JR, Shultz EK. The use of receiver operating characteristic (ROC) curves in test performance evaluation. Arch Pathol Lab Med1986;110:13-20.
13. Manning F, Baskett T, Morrison I, Lange I. Fetal biophysical profile scoring: A prospective study in 1,184 high-risk patients. Am J Obstet Gynecol1981;140:289-294.
14.
14. Williams K. Amniotic fluid assessment. Obstet Gynecol Surv1993;48:795-800.
15.
15. Blake GD, Knuppel RA, Ingardia CJ, et al. Evaluation of non-stress fetal heart rate testing in multiple pregnancy. Obstet Gynecol1984;63:528-532.
16.
16. Leveno KJ, Santos-Ramos R, Duenhoelter JH, et al. Sonar cephalometry in twin pregnancy: Discordancy of the biparietal diameter after 28 weeks' gestation. Am J Obstet Gynecol1980;138:615-619.
