Normal Amniotic Fluid Index at 28 Weeks

During a normal pregnancy, amniotic fluid volume increases progressively with gestational age. What is the normal range for the Amniotic Fluid Index (AFI) at 28 weeks?

Normal AFI Range at 28 Weeks

At 28 weeks’ gestation, an AFI of ≥8 cm but <25 cm is considered within the normal range. Throughout pregnancy, the AFI naturally fluctuates, yet remains within defined physiological limits. If the AFI falls to ≤5 cm at any point during pregnancy, intervention to increase amniotic fluid volume may be required. Oligohydramnios (low amniotic fluid) is associated with risks including fetal structural abnormalities and impaired pulmonary development, and may also correlate with congenital anomalies.

When oligohydramnios occurs, its underlying cause may not always be readily identifiable. In cases of late-pregnancy oligohydramnios, timely delivery—using an appropriate method—should be considered. Conversely, if the AFI reaches ≥25 cm, polyhydramnios (excessive amniotic fluid) is suspected. Polyhydramnios is also associated with fetal anatomical abnormalities—including those involving the eyes—and warrants close monitoring of maternal blood glucose levels, as gestational diabetes mellitus is a common contributing factor. If polyhydramnios is idiopathic (of unknown origin), no specific treatment may be necessary.

Both oligohydramnios and polyhydramnios may adversely affect fetal growth and development and increase the risk of intrauterine hypoxia. Pregnant individuals should therefore closely monitor their own physical symptoms, attend scheduled prenatal visits regularly, and engage in appropriate aerobic exercise—beneficial for facilitating vaginal delivery. We hope this information is helpful. Wishing you good health and happiness!