Comparison of the amniotic fluid index with gray-scale and color Doppler ultrasound

Addition of Color Doppler Sonography for Detection of Amniotic Fluid Disturbances and Its Implications on Perinatal Outcomes

OBJECTIVES

To determine whether color Doppler sonography increases the detection of pregnancies at risk for adverse outcomes.

METHODS

Participants admitted to labor and delivery with the anticipation of a vaginal delivery underwent measurements of amniotic fluid volume (AFV) using amniotic fluid index (AFI) and single deepest pocket (SDP) techniques by grayscale followed by color Doppler sonography. Oligohydramnios was defined as an AFI of less than 5 cm or an SDP of less than 2 cm. Intrapartum and perinatal outcomes were compared between participants with a diagnosis of a low AFV by grayscale and color Doppler sonography.

RESULTS

Over 42 months, 428 women were enrolled in the study. Color Doppler sonography resulted in lower AFV estimates (mean ± SD by the AFI, 10.7 ± 3.7 cm by grayscale sonography and 8.6 ± 3.6cm by color Doppler sonography; P < .0001). For the SDP, the mean AFVs were 4.6 ± 2.0 cm by grayscale sonography and 3.4 ± 1.4 cm by color Doppler sonography (P < .0001). The level of agreement between grayscale and color Doppler sonography in estimating the AFV was fair, with κ = 0.32 for the AFI and 0.28 for the SDP. Outcome measures of AFVs classified as low based on color Doppler sonography (normal by grayscale sonography) and those classified as low by grayscale sonography (low by color Doppler sonography) were compared. There was no difference in composite perinatal complications, mode of delivery, or composite neonatal complications.

CONCLUSIONS

The use of color Doppler sonography leads to the overdiagnosis of low AFVs and does not appear to increase the detection of pregnancies destined for adverse intrapartum or perinatal outcomes.

Antenatal fetal surveillance "Assessment of the AFV"

The evaluation of amniotic fluid volume (AFV) is an established part of the antenatal surveillance of pregnancies at risk for an adverse pregnancy outcome. The two most commonly used ultrasound techniques to estimate AFV are the amniotic fluid index (AFI) and the single deepest pocket (SDP). Four studies have defined normal AFVs, and although their normal volumes have similarities, there are also differences primarily due to the statistical methodology used in each study. Dye-determined AFV correlates with ultrasound estimates for normal fluid volumes but correlates poorly for oligohydramnios and polyhydramnios. The addition of color Doppler in estimating AFV leads to the overdiagnosis of oligohydramnios. Neither the AFI nor the SDP is superior in identifying oligohydramnios, but the SDP is a better measurement choice as the use of AFI increases the diagnosis rate of oligohydramnios and labor inductions without an improvement in pregnancy outcomes.