Oligohydramnios: ultrasonically detected incidence and subsequent fetal outcome

Oligohydramnios is a hallmark for intrauterine growth retardation (IUGR) and has been evaluated in populations suspected of having IUGR. We chose to evaluate its incidence in a routine obstetric population. During a 16-month period, ultrasound scans were performed on 1,408 patients. Severe oligohydramnios was identified in six patients (0.43%); Two infants had congenital malformations, and four had severe IUGR. A subset of 317 patients scanned within 2 weeks of delivery was reviewed. Although none of the patients fulfilled our original criterion of oligohydramnios (absence of a pocket of amniotic fluid 1 cm or more in broadest diameter), three of six small-for-gestational age infants had a subjective decrease in amniotic fluid volume for their stated gestational age. By changing the criterion of oligohydramnios to a subjective decrease in amniotic fluid volume, the sensitivity of this ultrasonic marker was increased to 50% and the specificity to 100%. We believe that the semiquantitative assessment of amniotic fluid volume can effectively screen for IUGR and thereby delineate a population, regardless of gestational age, that is at risk for perinatal morbidity and mortality.