Diagnostic ultrasound ( PDFDrive )

CHAPTER 39 The Fetal Urogenital Tract 1341
TABLE 39.2 Amniotic Fluid Index Values in Normal Pregnancy
AMNIOTIC FLUID INDEX (cm)
Gestational
Age (wk)
No.
5th
Percentile
10th
Percentile
50th
Percentile
Mean
90th
Percentile
95th
Percentile
14 50 2.8 3.1 5 5.4 8 8.6
15 50 3.2 3.6 5.4 5.7 8.2 9.1
16 50 3.6 4.1 5.8 6.1 8.5 9.6
17 50 4.1 4 6.3 6.6 9 10.3
18 50 4.6 5.1 6.8 7.1 9.7 11.1
19 50 5.1 5.6 7.4 7.7 10.4 12
20 50 5.5 6.1 8 8.3 11.3 12.9
21 50 5.9 6.6 8.7 8.9 12.2 13.9
22 50 6.3 7.1 9.3 9.6 13.2 14.9
23 50 6.7 7.5 10 10.3 14.2 15.9
24 50 7 7.9 10.7 11 15.2 16.9
25 50 7.3 8.2 11.4 11.7 16.1 17.8
26 50 7.5 8.4 12 12.3 17 18.7
27 50 7.6 8.6 12.6 12.8 17.8 19.4
28 50 7.6 8.6 13 13.3 18.4 19.9
29 50 7.6 8.6 13.4 13.6 18.8 20.4
30 50 7.5 8.5 13.6 13.8 18.9 20.6
31 50 7.3 8.4 13.6 13.8 18.9 20.6
32 50 7.1 8.1 13.6 13.7 18.7 20.4
33 50 6.8 7.8 13.3 13.4 18.2 20
34 50 6.4 7.4 12.9 13 17.7 19.4
35 50 6 7 12.4 12.5 16.9 18.7
36 50 5.6 6.5 11.8 11.8 16.2 17.9
37 50 5.1 6 11.1 11.1 15.3 16.9
38 50 4.7 5.5 10.3 10.3 14.4 15.9
39 50 4.2 5 9.4 9.4 13.7 14.9
40 50 3.7 4.5 8.6 8.6 12.9 13.9
41 50 3.3 4 7.8 7.7 12.3 12.9
With permission from Magann EF, Sanderson M, Martin JN, Chauhan S. The amniotic luid index, single deepest pocket, and two-diameter
pocket in normal human pregnancy. Am J Obstet Gynecol. 2000;182(6):1581-1588. 18
of ruptured membranes, maternal drug intake (e.g., angiotensinconverting
enzyme [ACE] inhibitors, 27 angiotensin II receptor
antagonists, 28 cyclooxygenase-2 [COX-2] selective and nonselective
inhibitors, 29 nonsteroidal antiinlammatory drugs, 30 cocaine 31 ),
or evidence of intrauterine growth restriction (IUGR), UT
anomalies must be strongly suspected. In the setting of a UT
abnormality, normal AFV indicates a good prognosis. Oligohydramnios
in the early second trimester carries a very poor
prognosis because of the associated pulmonary hypoplasia.
Occasionally and paradoxically, polyhydramnios may occur,
especially with unilateral obstructive uropathy, with mesoblastic
nephroma, or when there are concomitant abnormalities of the
central nervous system (CNS) or gastrointestinal (GI) tract.
he following questions are helpful in deining and characterizing
the UT abnormality:
• Is the bladder identiied and normal in appearance?
• Are kidneys present? Are they normal in position, size, and
echogenicity? Are renal cysts identiied?
• Is the UT dilated? If so, to what degree, at which level, and
what is the cause?
• Is the involvement unilateral or bilateral, symmetrical or
asymmetrical?
• What is the fetal gender?
It is important to perform a detailed anatomic scan to search
for associated abnormalities, which may indicate the presence
of a syndrome or chromosomal abnormality. Renal anomalies
may be part of the VATER association (vertebral defects, anal
atresia, tracheoesophageal istula, radial defects, and renal
anomalies). An expansion of this syndrome, VACTERL, includes
cardiac and nonradial limb defects. Associated nonurinary
anomalies have been reported in 34% of infants with CAKUT,
most common in the musculoskeletal, digestive, cardiovascular,
and central nervous systems. 32 When there are additional
malformations, the risk for fetal chromosomal abnormalities is
substantially increased compared with the maternal age–related
risk: 30 times higher for multiple defects versus 3 times higher
for isolated renal defect. 33
In addition, renal ultrasound is recommended for parents
(and siblings) of fetuses suspected to have certain renal