Amniotic fluid volume: ultrasound assessment and clinical significance.

Abstract

T HE ASSOCIATION between abnormalities of amniotic fluid volume (AFV) and altered perinatal outcome has long been recognized. ’ Oligohydramnios is associated with fetal dysmaturity syndromes (ie, postmaturity and intrauterine growth retardation [IUGR]) and with fetal congenital anomalies (ie, renal agenesisfdysgenesis). 12 Polyhydramnios, on the other hand, is associated with a variety of maternal (ie, diabetes mellitus, Rh isoimmunization) and fetal (open neural tube defects, gastrointestinal tract obstruction) conditions.L.3 In all the above conditions, perinatal mortality (PNM) and morbidity are known to be increased.’ 3 Antenatal recognition of both oligohydramnios and polyhydramnios has traditionally been based upon clinical examination of the patient. A symphysis-fundal height either less than or greater than that expected for gestational age should alert the practitioner to the possibility of their presence. The inaccuracies of clinical assessment of AFV for detection of these conditions is well recognized and has, over the years, prompted a search for more reliable methods for detecting both oligohydramnios and polyhydramnios. These methods have included both radiologic (plain abdominal xray, amniography) and sonographic (measurement of total intrauterine volume) techniques.4,5 The results of these methods, which are either invasive or time-consuming, or both, have been disappointing, and a simple clinically applicable and relevant method for assessing AFV is needed. More simple methods for assessment of AFV using real time ultrasound have been reported recently by several authors.6,7 Philipson et al have outlined subjective sonographic criteria for the identification of oligohydramnios and have found a significant relationship between their findings and the incidence of IUGR.6 Similarly, Zamah et al have outlined subjective sonographic criteria for the identification of polyhydramnios and have reported a significant relationship between their findings and the incidence of fetal congenital defects.’ The subjective nature of both of these authors’ criteria for identification of oligohydramnios and polyhydramnios, respectively, limit their