The demographic characteristics of the one hundred and seventy (170) participants are summarized in table 1. Seventy eight (78) women had a centrally located placenta (Group A) while 92 had a laterally located placenta (Fig. 2). Mean gestational age at recruitment was 22 weeks for group A and 21 weeks for group B.
There were no significant differences between the age,
weight,
height,
BMI and parity between both groups. Seven (8.9%) of women in group A developed PrE compared to 6 (6.5%) women in group B (Fig. 3).
Overall,
there were no significant statistical differences in demographic characteristics between the groups.
Table 1: Demographic characteristics and outcomes in subjects
|
CENTRAL N=78
|
LATERAL N=92
|
p-value
|
AGE (mean ±SD)
|
31.16 ± 5.59
|
31.92 ± 4.41
|
0.30
|
GA IN WEEKS (mean ±SD)
|
22.67±6.12
|
21.95±3.25
|
0.31
|
WEIGHT (mean ±SD)
|
75.76±12.24
|
78.56±12.75
|
0.14
|
HEIGHT (mean ±SD)
|
1.60±.08
|
1.61±.06
|
0.97
|
BMI (mean ±SD)
|
29.53±.15
|
30.55±0.14
|
0.18
|
PARITY median (range)
|
1 (0 – 3)
|
1 (0 - 5)
|
0.82
|
PREVIOUS PE N (%)
|
4/79 (5.1)
|
3/97 (3.1)
|
0.78
|
Proportion with PrE N (%)
|
7/78 (8.9)
|
6/92 (6.5)
|
0.57
|
The mean uterine artery PI,
RI and SD ratio were slightly higher for subjects with centrally located placenta (Table 2).
This however was not statistically significant.
Table 2: Comparison of uterine artery Doppler indices based on placental location
|
Central
|
Lateral
|
t-test
|
p-value
|
AVERAGE PI
|
0.80±0.19
|
0.78±0.22
|
0.69
|
0.49
|
AVERAGE RI
|
0.52±.08
|
0.50±0.09
|
1.07
|
0.28
|
AVERAGE S/D ratio
|
2.14±0.39
|
2.09±0.43
|
0.89
|
0.37
|
|
There was no association between placental location and development of pre-eclampsia (X2 = 0.096,
p = 0.76) as demonstrated in Table 3.
Table 3: Association of Pre-eclampsia with placental location
|
Pre-eclampsia
|
X2 (p-value)
|
YES
|
N0
|
PLACENTAL LOCATION
|
CENTRAL
|
7/13 (53.8)
|
71/157 (45.2)
|
0.096 (0.76)
|
LATERAL
|
6/13 (46.2)
|
86/157 (54.8)
|
|
|
TOTAL
|
13 (100)
|
157 (100)
|
|
The sensitivity,
specificity,
positive predictive value,
negative predictive value (NPV) and Odds Ratio (OR) of uterine artery Doppler indices for predicting PrE for groups A and B are displayed in Tables 4 and 5 respectively.
In group A,
the PI had the highest specificity of 100%,
and PPV of 100% and NPV of 94.7%,
while the combined result had the greatest sensitivity of 57.1% and NPV of 95.7%,
with specificity of 94.4%,
and PPV of 50%.
In group B,
the PI test had the greatest specificity of 91.9% and PPV of 22.2% while the combined result and S/D ratio had similar sensitivities (50.0%).
Table 4: Accuracy of uterine Doppler indices for predicting PE in patients with central placenta
TEST
|
SENSITIVITY (%)
|
SPECIFICITY (%)
|
PPV
(%)
|
NPV
(%)
|
ODDS RATIO
(95% CI)
|
PI >95th centile
|
3/7
(42.9)
|
71/71 (100.0)
|
3/3
(100.0)
|
71/75
(94.7)
|
--
|
RI >95th centile
|
2/7
(28.6)
|
68/71
(93.2)
|
2/5
(40.0)
|
68/73
(93.2)
|
0.11
(0.02 – 0.82)
|
S/D >95th centile
|
3/7
(42.9)
|
67/71
(94.4)
|
3/7
(42.9)
|
67/71
(94.4)
|
0.08
(0.01 – 0.48)
|
Combined
|
4/7
(57.1)
|
67/71
(94.4)
|
4/8
(50.0)
|
67/70
(95.7)
|
0.05
(0.01 – 0.27)
|
Table 5: Accuracy of uterine Doppler indices for predicting PrE in patients with lateral placentas
TEST
|
SENSITIVITY (%)
|
SPECIFICITY (%)
|
PPV
(%)
|
NPV
(%)
|
ODDS RATIO
(95% CI)
|
PI >95th centile
|
2/6 (33.3)
|
79/86 (91.9)
|
2/9 (22.2)
|
79/83 (95.2)
|
0.18
(0.03 – 1.14)
|
RI >95th centile
|
1/6 (16.7)
|
72/86 (83.7)
|
1/15 (6.7)
|
72/77 (93.5)
|
0.97
(0.11 – 8.97)
|
S/D >95th centile
|
3/6 (50.0)
|
71/86 (82.6)
|
3/18 (16.7)
|
71/74 (95.9)
|
0.21
(0.04 – 1.15)
|
Combined
|
3/6 (50.0)
|
69/86 (80.2)
|
3/20 (15.0)
|
69/72 (95.8)
|
0.25
(0.05 – 1.33)
|
The ROC ( Fig. 4 ) and corresponding areas under the curves (Table 6) for group A show the combined test result has an AUC of 0.76: 95% CI: 0.53 -0.99,
followed by the PI test of 0.71,
95% CI: 0.46 -0.97.
Fig. 5
Table 6: AUC of uterine Doppler indices for predicting PrE in patients with central placentas
Area Under the Curve
|
Test Result Variable(s)
|
Area
|
Std.
Errora
|
Asymptotic Sig.b
|
Asymptotic 95% Confidence Interval
|
Lower Bound
|
Upper Bound
|
UTat NOTCH
|
.557
|
.123
|
.618
|
.316
|
.798
|
PI TEST
|
.714
|
.127
|
.063
|
.466
|
.963
|
RI TEST
|
.622
|
.126
|
.290
|
.374
|
.869
|
SD TEST
|
.686
|
.125
|
.106
|
.442
|
.930
|
COMBINED TEST
|
.758
|
.118
|
.025
|
.527
|
.988
|
b.
Null hypothesis: true area = 0.5
|
Fig. 5 shows that for patients with laterally located placentas (group B),
the accuracy of uterine artery Doppler was generally lower,
with the highest AUC of 0.66: 95% CI: 0.41 -0.91 obtained using the S/D test (Table 7).
Table 7: AUC of uterine Doppler indices for predicting PrE in patients with central placentas
Area Under the Curve
|
Test Result Variable(s)
|
Area
|
Std.
Errora
|
Asymptotic Sig.b
|
Asymptotic 95% Confidence Interval
|
Lower Bound
|
Upper Bound
|
UTat NOTCH
|
.620
|
.133
|
.327
|
.359
|
.881
|
PI TEST
|
.626
|
.134
|
.304
|
.364
|
.888
|
RI TEST
|
.502
|
.123
|
.987
|
.261
|
.743
|
SD TEST
|
.663
|
.127
|
.184
|
.414
|
.912
|
COMBINED TEST
|
.651
|
.127
|
.217
|
.403
|
.899
|
b.
Null hypothesis: true area = 0.5
|