Dunn et al evaluated the risk to the fetus of toxoplasmosis acquired by the mother during pregnancy. The estimates can help counsel patients and aid in post-partum monitoring of infants. The authors are from University College London, Hopital de la Croix-Rousse in Lyons, and Statens Serum Institut in Copenhagen.
Risk estimates:
(1) risk of the congenital infection based on the week of gestation at maternal seroconversion
(2) risk of an infected infant developing clinical signs (may not be symptomatic) based on the week of gestation at maternal seroconversion
If a mother seroconverts during pregnancy then the risk of congenital infection is shown in Figure 1 from which the following data is extrapolated.
|
week gestation |
upper 95% |
mean |
lower 95% |
|
0 |
4.1 |
1.6 |
0.3 |
|
4 |
4.1 |
1.6 |
0.3 |
|
8 |
5.1 |
2.8 |
0.3 |
|
12 |
8.4 |
5.8 |
2.2 |
|
16 |
15.2 |
11.1 |
6.8 |
|
20 |
25 |
19.8 |
14.7 |
|
24 |
37.7 |
31.2 |
24.2 |
|
28 |
53.5 |
47.3 |
38.6 |
|
32 |
67.6 |
60.8 |
50.8 |
|
36 |
79.8 |
71.4 |
57.3 |
|
40 |
89.8 |
78.4 |
61.4 |
from Figure 1 page 1830 Dunn
If the mean curve is modeled in JMP:
mean percent with congenital infection =
= (-0.000119 * ((week)^4)) + (0.00763 * ((week)^3)) - (0.074885 * ((week)^2)) + (0.329997 * (week)) + 1.44615
If the infection status of the fetus is not known then the risk of developing clinical signs before 3 years of age is shown in Figure 3. The mean line data is:
|
week of gestation |
mean percent |
|
0 |
0.5 |
|
4 |
0.8 |
|
8 |
1.1 |
|
12 |
3.2 |
|
16 |
5.3 |
|
20 |
8 |
|
24 |
9.5 |
|
27 |
10 |
|
28 |
9.9 |
|
32 |
8.5 |
|
36 |
6.4 |
|
40 |
4.6 |
from lower half of Figure 3, page 1831 Dunn et al
This can be modeled in JMP:
mean percent with clinical signs by 3 years with seroconversion over weeks 0 to 20 =
= (-0.000098 * ((week)^4)) + (0.003559 * ((week)^3)) - (0.016146 * ((week)^2)) + (0.05317 * (week)) + 0.5238095
mean percent with clinical signs by 3 years with seroconversion over weeks 20 to 28 =
= (-0.004613 * ((week)^3)) + (0.2977679 * ((week)^2)) - (6.01 * (week)) + 46
mean percent with clinical signs by 3 years with seroconversion over weeks 28 to 40 =
= (-0.45 * (week)) + 22.65
If the infection status of the infant is known, then the risk of developing clinical signs by 3 years of age steadily declines based on the week of gestation at maternal seroconversion, from almost 90% at week 0 to less than 10% at week 40 (upper half of Figure 3, page 1831, Dunn et al). Multiplying the data from the first figure by the data from this curve gives the curve for uncertain infection (see first column page 1832).
Specialty: Infectious Diseases
