Queenan et al simplified the interpretation of the change in optical density of amniotic fluid at 450 nm (delta OD 450). This can guide the management of a pregnant Rh negative woman with a potentially affected fetus. The authors are from Georgetown University Medical Center in Washington, DC.
Differences from earlier approaches:
(1) covers pregnancies from 14 to 40 weeks (not just 27 to 40 weeks)
(2) delta OD 450 is plotted as a linear variable (not LOG10)
(3) the decision lines are curves rather than straight
There are 4 zones separated by 3 lines.
|
Zone |
Limits |
|---|---|
|
intrauterine death risk |
above Line A |
|
affected |
between Line A and Line B |
|
indeterminate |
between Line B and Line C |
|
unaffected |
below Line C |
|
week |
Line A |
Line B |
Line C |
|---|---|---|---|
|
14 |
0.1500 |
0.1050 |
0.0520 |
|
15 |
|
0.1120 |
0.0580 |
|
16 |
|
0.1183 |
0.0650 |
|
17 |
|
0.1222 |
0.0700 |
|
18 |
0.1800 |
0.1240 |
0.0725 |
|
19 |
0.1800 |
0.1240 |
0.0750 |
|
20 |
0.1800 |
0.1230 |
0.0750 |
|
21 |
0.1800 |
0.1210 |
0.0750 |
|
22 |
0.1800 |
0.1166 |
0.0730 |
|
23 |
0.1750 |
0.1116 |
0.0710 |
|
24 |
|
0.1070 |
0.0680 |
|
25 |
|
0.1000 |
0.0640 |
|
26 |
|
0.0940 |
0.0600 |
|
27 |
|
0.0850 |
0.0540 |
|
28 |
|
0.0790 |
0.0500 |
|
29 |
0.1410 |
0.0717 |
0.0430 |
|
30 |
|
0.0628 |
0.0390 |
|
31 |
0.1310 |
0.0550 |
0.0340 |
|
32 |
|
0.0478 |
0.0289 |
|
33 |
|
0.0417 |
0.0233 |
|
34 |
|
0.0345 |
0.0195 |
|
35 |
|
0.0280 |
0.0155 |
|
36 |
|
0.0230 |
0.0120 |
|
37 |
|
0.0195 |
0.0089 |
|
38 |
|
0.0150 |
0.0067 |
|
39 |
|
0.0128 |
0.0060 |
|
40 |
0.0800 |
0.0100 |
0.0056 |
extracted from Figure 5, page 1374
|
Line |
Weeks |
delta OD 450 = |
|---|---|---|
|
A |
14-18 |
= (0.0075 * (weeks gestation)) + 0.045 |
|
A |
18-22 |
= 0.18 |
|
A |
22-40 |
= (-0.005562 * (weeks gestation)) + 0.30269 |
|
B |
14-22 |
= (-0.000823 * ((weeks gestation)^2)) + (0.03102 * (weeks gestation)) - 0.1679 |
|
B |
22-40 |
= (0.00002 * ((weeks gestation)^3)) - (0.001758 * ((weeks gestation)^2)) + (0.043859 * (weeks gestation)) - 0.21 |
|
C |
14-22 |
= (-0.000654 * ((weeks gestation)^2)) + (0.026199 * (weeks gestation)) - 0.187045 |
|
C |
22-40 |
= (0.0000178 * ((weeks gestation)^3)) - (0.001585 * ((weeks gestation)^2)) + (0.04168 * (weeks gestation)) - 0.26628 |
Specialty: Obstetrics & Gynecology, Clinical Laboratory
ICD-10: ,
