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.