Reference Ranges of Amniotic Fluid Index in Late Third Trimester of Pregnancy: What Should the Optimal Interval between Two Ultrasound Examinations Be?

Table 1

AFI values from 34 to 40 weeks; mean, standard deviation, and percentile values (all in centimeters).

Gestational age	Mean	Standard deviation	5th percentile	10th percentile	50th percentile	90th percentile	95th percentile
34 weeks	14.59	1.79	11.7	12.0	14.6	17.0	17.3
35 weeks	14.25	1.57	11.1	11.8	14.2	16.2	16.4
36 weeks	13.17	1.56	10.6	11.0	13.2	15.3	15.7
37 weeks	12.48	1.52	10.1	10.2	12.6	14.7	15.1
38 weeks	12.20	1.70	9.8	10.0	12.1	14.4	14.7
39 weeks	11.37	1.71	8.8	9.1	11.4	14.0	14.4
40 weeks	10.99	1.55	8.7	8.8	10.8	13.5	13.7