Which of the following is NOT true about amniotic fluid index (AFI)?

Amniotic fluid index (AFI) is calculated by adding the veical depths of the largest pocket in each of four equal uterine quadrants. Significant hydramnios is defined by an index greater than 24 cm. Fluid restriction or dehydration may lower the AFI. Peak AFI is seen at approximately 32 weeks followed by a steady decline until 42 weeks. Ref: Cunningham F.G., Leveno K.J., Bloom S.L., Hauth J.C., Rouse D.J., Spong C.Y. (2010). Chapter 21. Disorders of Amnionic Fluid Volume. In F.G. Cunningham, K.J. Leveno, S.L. Bloom, J.C. Hauth, D.J. Rouse, C.Y. Spong (Eds), Williams Obstetrics, 23e.