Sociodemographic and clinical characteristics
The distributions of socio-demographic and clinical characteristics of pregnancy syphilis cases and controls are shown in Table 1, and there were no significant differences between cases and controls on the matched variable (Age). Compared to the control group, the median age of pregnancy syphilis was 28 years (range, 16–53 years). Most cases and controls are in the 25-29 age group (39.2%;41.0%), which is consistent with the results of a 10-year review in Shenzhen, China(25).
There were significant differences in the distribution of study places, the urban population in the case group accounted for 62.3% (248/398). Between the two groups, there are also significant differences in the lack of paid occupations, the great majority of which are lack of paid occupations (71.6%; 62.6%). Compared to the non-syphilitic pregnant women control group, Abortion, Turbid amniotic fluid, APOs have significant differences(P<0.01). Among the biochemical indicators, the contents of CRP are different in the two groups (p<0.05). Prevalence of HDP (n=49,12.3%) and viral hepatitis (n=22,3.8%) increased significantly in the case group, while the prevalence of HDP(n=15,3.8%) and viral hepatitis(n=4,1.0%) was lower in the control group (p<0.05)
Table 1. The distributions of General demographic characteristics of pregnancy syphilis cases and controls.
|
N (%)
|
|
Characteristic
|
Case
|
Control
|
P value
|
|
N=398(%)
|
N=398(%)
|
|
Age, years
|
|
|
|
(mean ± Standard deviation)
|
28.40 ± 5.357
|
28.97 ± 4.861
|
---
|
Age, years
|
|
|
|
15-24
|
94 (23.6)
|
73(18.3)
|
0.207
|
25-29
|
156 (39.2)
|
163(41.0)
|
|
30-34
|
91(22.9)
|
109(27.4)
|
|
35-53
|
57(14.3)
|
53(13.3)
|
|
Table1. Continued
|
N (%)
|
|
Characteristic
|
Case
|
Control
|
P value
|
|
N=398(%)
|
N=398(%)
|
|
Absence of paid occupation
Yes
No
|
285(71.6)
113(28.4)
|
249(62.6)
149(37.4)
|
0.007
|
Present residence
City
rural
|
248(62.3)
150(37.7)
|
279(70.1)
119(29.9)
|
0.020
|
Dysmenorrhea
Yes
No
|
79 (19.8)
319(80.2)
|
94 (23.7)
303(76.3)
|
0.198
|
Abortion
0
1
≥2
|
186(46.7)
120(24.4)
96 (28.9)
|
259(65.1)
97 (30.2)
42 (4.7)
|
<0.01
|
HDP
Yes
No
|
49 (12.3)
349(87.7)
|
15 (3.8)
383 (96.2)
|
<0.01
|
Maternal anemia
Yes
No
|
129(32.4)
269(67.6)
|
132 (33.2)
266 (66.8)
|
0.821
|
Gestational diabetes
|
|
|
|
Yes
|
41(10.3)
|
49(12.3)
|
0.371
|
No
|
357(89.7)
|
349(87.7)
|
|
Viral hepatitis
|
|
|
|
Yes
|
22 (5.5)
|
4(1.0)
|
0.001*
|
No
|
376(94.5)
|
394 (99.0)
|
|
PROM
|
|
|
|
Yes
|
71(17.8)
|
69 (17.3)
|
0.852
|
No
|
327(82.2)
|
329 (82.7)
|
|
Placental abruption
|
|
|
|
Yes
|
2 (0.5)
|
3 (0.8)
|
1.000*
|
No
|
396 (99.5)
|
396 (99.5)
|
|
Table1. Continued
|
|
|
|
|
N (%)
|
|
Characteristic
|
Case
|
Control
|
P value
|
|
N=398(%)
|
N=398(%)
|
|
Turbid amniotic fluid
|
|
|
|
High
|
109(27.4)
|
28 (7.0)
|
<0.01
|
Low
|
289(72.6)
|
370 (93.0)
|
|
Umbilical cord abnormality
|
|
|
|
Yes
|
99(24.9)
|
115 (28.9)
|
0.201
|
No
|
299(75.1)
|
283 (71.1)
|
|
APOs
|
|
|
|
Yes
|
52 (13.1)
|
3 (0.8)
|
<0.01*
|
No
|
346 (86.9)
|
395 (99.2)
|
|
CRP
|
|
|
|
Normal
|
276 (69.3)
|
332 (83.4)
|
<0.01
|
Elevated (>10mg/L)
|
122 (30.7)
|
66 (16.6)
|
|
* Corrected chi-square value
APOs, Adverse pregnancy outcome; CRP, High-sensitivity C-reactive protein;
PROM, Premature rupture of membranes; HDP, Hypertensive disorders of pregnancy;
Logistic Regression Modelling
In the Univariate analysis, all factors related to syphilis were included in the Multivariable model (based on P value ≤ 0.05; Table 2). After adjustment age, Absence of paid occupation, Non-urban population, variables that were retained in the final multivariable model (Table 2) were: Absence of paid occupation (OR 1.536, CI 1.106–2.134)、Abortion 1 time and ≥2 times (OR 1.770, CI 1.242–2.523)(OR 3.128, CI 2.015–4.857)、 HDP (OR 2.017, CI 1.042–3.906)、Viral hepatitis (OR 4.702, CI 1.544–14.318)、Turbid amniotic fluid (OR 2.945, CI 1.762–4.923)、APOs (OR 7.428, CI 2.137–25.820), CRP (≥10mg/L) (OR 1.817, CI 1.249–2.643).
Table 2. Logistic regression model results of pregnancy syphilis cases and controls.
Variable
|
Bivariable analysis
|
P
value
|
Multivariable analysis
|
P
value
|
OR
|
95% CI
|
a OR
|
95% CI
|
Absence of paid occupation
|
1.509
|
0.492-0.892
|
0.007
|
1.536
|
1.106-2.134
|
0.010
|
Non-urban population
|
1.418
|
1.056-1.905
|
0.02
|
--
|
--
|
--
|
history of abortion
|
|
|
|
|
|
|
0
|
ref
|
--
|
--
|
--
|
--
|
--
|
1
|
1.723
|
1.242-2.390
|
0.001
|
1.770
|
1.242-2.523
|
0.002
|
>=2
|
3.050
|
2.023-4.599
|
0.013
|
3.128
|
2.015-4.857
|
<0.001
|
HDP
|
3.585
|
1.957-6.508
|
<0.001
|
2.017
|
1.042-3.906
|
0.037
|
Viral hepatitis
|
5.763
|
1.968-16.881
|
0.001
|
4.702
|
1.544-14.318
|
0.006
|
Turbid amniotic fluid
|
4.984
|
3.201-7.761
|
<0.001
|
2.945
|
1.762-4.923
|
<0.001
|
APOs
|
19.788
|
6.125-63.928
|
<0.001
|
7.428
|
2.137-25.820
|
0.002
|
CRP (≥10mg/L)
|
2.224
|
1.584-3.122
|
<0.001
|
1.817
|
1.249-2.643
|
0.002
|
a OR, Adjusted odds ratio; CI, confidence interval; HDP, Hypertensive disorders of pregnancy; APOs, Adverse pregnancy outcome; CRP, High-sensitivity C-reactive protein;
Analysis of related factors of HDP in syphilis
The results of multivariate analysis of syphilis-related factors demonstrated that patients with syphilis had an increased risk of HDP (aOR2.017,95% CI1.042-3.906), so we further explored the factors related to HDP. Using the propensity score method, after controlling for age, occupation, ethnicity, parity, and urine protein, 49 HDP patients were matched 1:3 with non-HDP patients, and a total of 147 non-HDP patients were matched. Univariate and Multivariate analyses were performed on 49 HDP patients and 147 non-HDP patients (Table 3).
The mean age of the HDP group (27.76) was lower than that of the Non-HDP group (28.13), and there was no significant difference in the incidence of the age groups (P<0.05). In pregnant syphilis patients, compared with the Non-HDP group, Dysmenorrhea (42.9%), Maternal anemia (61.2%), Total cholesterol (55.1%) of the HDP group were higher than the Non-HDP group: Dysmenorrhea (13.6%), Maternal anemia (29.3%), Total cholesterol (34.0%).
Dysmenorrhea history remained positively associated with HDP [adjusted odds ratio [(a OR) 5.413, 95% CI 2.410-12.158]. Associations between HDP and Maternal anemia were noted (a OR)3.808, 95%CI1.833-7.911). Compared with Normal Total cholesterol, Total cholesterol (>=5.69mmol/L) was positively correlated with HDP [(a OR) 3.144, 95% CI 1.485-6.655].
Table 3. Univariate and multivariate analysis results of HDP cases and control.
Hierarchical level/Characteristics
|
HDP
(N=49)
|
Non-HDP
(N=147)
|
Crude OR
(95%CI)
|
P
|
Adjusted
OR
(95% CI)
|
P
|
Age, years
(mean ± Standard deviation)
|
49
27.76±5.510
|
147
28.13±5.142
|
0.986
(0.927-1.050)
|
0.664
|
---
|
---
|
Age, group
|
|
|
|
|
|
|
15-24
|
16(32.7)
|
38(25.9)
|
---
|
---
|
---
|
---
|
25-29
|
16(32.7)
|
58(39.5)
|
0.655
(0.293-1.465)
|
0.303
|
---
|
---
|
30-34
|
7(14.3)
|
29(19.7)
|
0.573
(0.209-1.576)
|
0.281
|
---
|
---
|
35-53
|
10(20.4)
|
22(15.0)
|
1.080
(0.418-2.788)
|
0.874
|
---
|
---
|
Absence of paid occupation
|
17(34.7)
|
50(34.0)
|
1.031
(0.522-2.034)
|
0.931
|
---
|
---
|
Non-urban population
|
19(38.8)
|
59(40.1)
|
1.059
(0.546-2.053)
|
0.866
|
---
|
---
|
Dysmenorrhea
|
21(42.9)
|
20(13.6)
|
4.762
(2.280-9.947)
|
<0.001
|
5.413
(2.410-12.158)
|
<0.001
|
Abortion
|
|
|
|
|
|
|
0
|
20(40.8)
|
75(51.0)
|
---
|
---
|
---
|
---
|
1
|
17(34.7)
|
41(27.9)
|
1.555
(0.734-3.293)
|
0.249
|
---
|
---
|
≥2
|
12(24.5)
|
31(21.1)
|
1.452
(0.634-3.326)
|
0.378
|
---
|
---
|
Un-treatment in pregnancy
|
37(75.5)
|
118(80.3)
|
1.320
(0.613-2.843)
|
0.479
|
---
|
---
|
Table3. Continued
Hierarchical level/Characteristics
|
HDP
(N=49)
|
Normal
(N=349)
|
Crude OR
(95%CI)
|
P
|
Adjusted
OR
(95% CI)
|
P
|
RPR titer(≥1:8)
|
22(44.9)
|
45(30.6)
|
1.847
(0.951-3.585)
|
0.070
|
---
|
---
|
APOs
|
9(18.4)
|
19(12.9)
|
1.516
(0.636-3.614)
|
0.348
|
---
|
---
|
Placental abruption
|
1(2.0)
|
1(0.7)
|
3.042
(0.187,49.567)
|
0.435
|
---
|
---
|
Gestational diabetes
|
2(4.1)
|
15(10.2)
|
0.374
(0.083,1.699)
|
0.203
|
---
|
---
|
Maternal anemia
|
30(61.2)
|
43(29.3)
|
3.819
(1.943-7.505)
|
<0.001
|
3.808
(1.833-7.911)
|
<0.001
|
CRP (≥10mg/L)
|
18(36.7)
|
48(32.7)
|
1.198
(0.610-2.353)
|
0.601
|
---
|
---
|
Total cholesterol
(>5.69mmol/L)
|
27(55.1)
|
50(34.0)
|
2.381
(1.233-4.599)
|
0.010
|
3.144
(1.485-6.655)
|
0.003
|
a OR, Adjusted odds ratio; CI, confidence interval; CRP, High-sensitivity C-reactive protein; RPR, rapid plasma reagin ring card test; PROM, Premature rupture of membranes;
APOs, Adverse pregnancy outcome;