The study population consisted of 59 women. Maternal and fetal characteristics are presented in Table 1. The median incubation period from presentation to the clinic to an adverse event was 6,2 weeks. Half of the pregnancies (30 of 59 pregnancies, 52.5%) did not develop any adverse event. In the remaining 29 pregnancies 9 cases developed pre-eclampsia (15.25%), 18 cases showed deterioration on the fetal Doppler studies and/or on cardio-tocography, there was one intra-uterine death and one termination of the pregnancy. In the index visit 12 women were on low-dose aspirin, 7 on low molecular weight heparin and 2 were receiving both treatments. Figure 1 shows the Kaplan-Meier curve for the time elapsing between the first examination and the occurrence of an adverse event.
The results of the univariate analysis showed that gestational hypertension, greater systolic and diastolic blood pressure and increased PLGF (expressed either as raw values or as multiples of the median) were the maternal parameters associated with an adverse event (Table 2). Accordingly, fetal parameters related to an adverse event were low AC and EFW centile, increased UA PI and reduced CP ratio. In half of the cases (31 of the 59 cases, 52.5%) the mothers were normotensive and fetal Doppler parameters were normal in the index visit.
PLGF was the strongest predictor of adverse events. ROC analysis was performed for the prediction of adverse events by PLGF expressed in raw values and PLGF MOM (Fig. 2). PLGF raw values and PLGF MOM both had equally good predictive ability (AUC 0.82 and 0.78 respectively). Optimal cut-off points were 177.7pg/ml for PLGF raw values (sensitivity 83% and specificity 66.7%) and 0.277 MoM (sensitivity 76% and specificity 86.7%). Kaplan-Meier curves of PLGF raw values and PLGF MoM levels for the prediction of time to adverse events are shown in Fig. 3.
On multiple Cox regression analysis maternal systolic blood pressure and PLGF and fetal increased umbilical artery PI and reduced CP ratio were independently associated with adverse events (Table 3). PLGF raw values and PLGF MoM performed equally well in the analysis (hazard ratio 5.19 (95% CI: 1.69–15.9) for PLGF < 177.7pg/ml and hazard ratio 5.03 (95% CI: 1.79–14.15) for PLGF MoM).
Table 1. Maternal and fetal characteristics of the study population (N=59)
BMI=body mass index, SGA=small for gestational age, AC=fetal abdominal circumference, HC=fetal head circumference, FL= fetal femur length, EFW= estimated fetal weight, UA PI=umbilical artery pulsatility index, CP ratio=cerebro-placental ratio, SBP=systolic blood pressure, DBP=diastolic blood pressure, PLGF=placental growth factor, MoM=multiples of the median, SD=standard deviation, IQR=inter-quartile range.
Maternal and fetal parameters were recorded at the first (index) visit.
Table 2. Maternal and fetal parameters associated with adverse events by Univariate Cox regression analysis. BMI=body mass index, SGA=small for gestational age, AC=fetal abdominal circumference, HC=fetal head circumference, FL= fetal femur length, EFW= estimated fetal weight, UA PI=umbilical artery pulsatility index, CP ratio=cerebro-placental ratio, SBP=systolic blood pressure, DBP=diastolic blood pressure, PLGF=placental growth factor, MoM=multiples of the median, SD=standard deviation, IQR=inter-quartile range.
|
Adverse event
|
|
|
No (N=30; 50.8%)
|
Yes (N=29; 49.2%)
|
|
|
N (%)
|
N (%)
|
HR (95% CI)+
|
P
|
Maternal age, mean (SD)
|
31.3 (5.8)
|
32.4 (5.2)
|
1.02 (0.95 - 1.08)
|
0.617
|
Maternal BMI, mean (SD)
|
24.1 (5.2)
|
24.3 (5.4)
|
1.02 (0.95 - 1.09)
|
0.646
|
BMI
|
Underweight/ Normal
|
20 (54.1)
|
17 (45.9)
|
|
|
Overweight/ Obese
|
10 (45.5)
|
12 (54.5)
|
1.36 (0.65 - 2.86)
|
0,415
|
Weight gain (up to first visit) , mean (SD)
|
8.6 (6.4)
|
8.5 (4.8)
|
1.00 (0.93 - 1.08)
|
0.968
|
Smoking
|
No
|
22 (47.8)
|
24 (52.2)
|
|
|
Yes
|
8 (61.5)
|
5 (38.5)
|
0.67 (0.26 - 1.77)
|
0.423
|
Parity
|
0
|
15 (40.5)
|
22 (59.5)
|
|
|
>=1
|
15 (68.2)
|
7 (31.8)
|
0.50 (0.21 - 1.17)
|
0.111
|
Previous SGA
|
No
|
25 (49)
|
26 (51)
|
|
|
Yes
|
5 (62.5)
|
3 (37.5)
|
0.70 (0.21 - 2.33)
|
0.563
|
Gestational hypertension
|
No
|
29 (53.7)
|
25 (46.3)
|
|
|
Yes
|
1 (20)
|
4 (80)
|
4.08 (1.37 - 12.10)
|
0.011
|
Gestational diabetes
|
No
|
26 (50)
|
26 (50)
|
|
|
Yes
|
4 (57.1)
|
3 (42.9)
|
1.16 (0.35 - 3.89)
|
0.805
|
Gestational age at SGA diagnosis, mean (SD)
|
31.7 (2.8)
|
30.3 (4)
|
0.98 (0.87 - 1.09)
|
0.698
|
AC centile, median (IQR)
|
8.4 (4.8 ─ 12.1)
|
2 (0.4 ─ 4.4)
|
0.85 (0.76 - 0.94)
|
0.002
|
HC centile, median (IQR)
|
10.3 (2.7 ─ 21.2)
|
3.5 (0.5 ─ 8.6)
|
0.97 (0.94 - 1.00)
|
0.057
|
FL centile, median (IQR)
|
11.2 (1.4 ─ 21.3)
|
3.8 (0.8 ─ 8.4)
|
0.97 (0.93 - 1.01)
|
0.093
|
EFW centile, median (IQR)
|
6.4 (3.5 ─ 10)
|
2.2 (0.7 ─ 4.5)
|
0.82 (0.72 - 0.93)
|
0.002
|
UA PI≥90th
|
No
|
28 (60.9)
|
18 (39.1)
|
|
|
Yes
|
2 (15.4)
|
11 (84.6)
|
3.91 (1.81 - 8.45)
|
0.001
|
CP ratio≤10th
|
No
|
24 (61.5)
|
15 (38.5)
|
|
|
Yes
|
6 (30)
|
14 (70)
|
3.32 (1.57 - 7.03)
|
0.002
|
UT PI centile, median (IQR)
|
87 (61.1 ─ 99.3)
|
96.7 (79.7 ─ 100)
|
1.02 (1.00 - 1.03)
|
0.073
|
SBP, mean (SD)
|
109.8 (13.2)
|
124.5 (20.3)
|
1.03 (1.02 - 1.05)
|
<0.001
|
DBP, mean (SD)
|
71.3 (9.6)
|
81.9 (15.8)
|
1.05 (1.02 - 1.08)
|
0.001
|
PLGF (pg/ml), median (IQR)
|
211.2 (119.2 ─ 389.8)
|
55.4 (34.7 ─ 118.4)
|
0.59 (0.41 - 0.84)
|
0.003
|
PLGF (pg/ml) ≥177.7
|
20 (80.0)
|
5 (20.0)
|
|
|
<177.7
|
10 (29.4)
|
24 (70.6)
|
6.19 (2.33 – 16.43)
|
<0.001
|
PLGF MoM, median (IQR)
|
0.57 (0.3 ─ 0.86)
|
0.13 (0.06 ─ 0.28)
|
0.22 (0.07 - 0.73)
|
0.013
|
Table 3. Multivariate Cox regression analysis for the prediction of adverse events in the study population. UA-PI≥90=umbilical artery pulsatility index≥90th centile, CP ratio≤10= cerebro-placental ratio ≤10th centile, SBP=systolic blood pressure, PLGF=placental growth factor, MoM=multiples of the median
|
|
HR (95% CI)+
|
P
|
UA PI≥90
|
No (reference)
|
|
|
Yes
|
2.48 (1.03 ─ 5.95)
|
0.042
|
CP ratio≤10
|
No (reference)
|
|
|
Yes
|
2.73 (1.10 ─ 6.79)
|
0.030
|
|
|
|
|
SBP
|
|
1.03 (1.01-1.06)
|
0.005
|
PLGF MoM
|
>0.277 (reference)
|
|
|
|
≤0.277
|
5.03 (1.79 - 14.15)
|
0.002
|
+Hazard Ratio (95% Confidence Interval)