Doppler ultrasonography can be used to measure the middle cerebral artery peak systolic velocity (MCA PSV). Multiples of the median for the arterial flow velocity correlate with multiples of the median for fetal hemoglobin. This can provide a noninvasive method for diagnosis of fetal anemia.
|
Week of Gestation |
Median Fetal Hemoglobin in g/dL |
Median MCA PSV in cm/sec |
|
18 |
10.6 |
23.2 |
|
20 |
11.1 |
25.5 |
|
22 |
11.6 |
27.9 |
|
24 |
12.0 |
30.7 |
|
26 |
12.3 |
33.6 |
|
28 |
12.6 |
36.9 |
|
30 |
12.8 |
40.5 |
|
32 |
13.1 |
44.4 |
|
34 |
13.3 |
48.7 |
|
36 |
13.5 |
53.5 |
|
38 |
13.6 |
58.7 |
|
40 |
13.8 |
64.4 |
from Table 1 (page 11) and Table 3 (page 12
When these are entered into JMP, the following equations can be derived:
median hemoglobin in g/dL =
= (-0.004439 * ((week of gestation)^2)) + (0.397515 * (week of gestation)) + 4.94213
median MCA-PSV in cm/sec =
= (0.0426823 * ((week of gestation)^2)) - (0.627323 * (week of gestation)) + 20.92867
Mari et al give the following equations for expected hemoglobin and MCA-PSV:
expected median fetal hemoglobin in g/dL =
= EXP(2.84 - (8.55 / (weeks of gestation))
expected median MCA-PSV =
= EXP(2.31 + (0.046 * (weeks of gestation))
measured MCA-PSV as multiple of expected median MCA-PSV=
= (measured MCA-PSV) / (expected MCA-PSV)
hemoglobin of the fetus as multiples of the median (MoM) =
= (0.2861 * ((MoM of MCA-PSV)^3)) – (1.2885 * ((MoM of MCA-PSV)^2)) + (1.2794 * (MoM of MCA-PSV)) + 0.6835
predicted hemoglobin for fetus at birth =
= (predicted MoM based on MCA PSV) * (predicted median hemoglobin for gestational age)
Interpretation:
• The lower the hemoglobin as a multiple of the expected median, the more severe the fetal anemia.
|
Hemoglobin as Multiple of Expected Median |
Severity of Anemia |
|
> 0.83 |
none |
|
0.65 to 0.83 |
mild |
|
0.55 to 0.64 |
moderate |
|
< 0.55 |
severe |
Specialty: Obstetrics & Gynecology, Pedatrics
ICD-10: ,
