Table 1 Characteristics of pregnant women and partners

Demographics*

Age

 Median (years, IR)

27 (25–29)

29 (27–32)

27 (24–29)

 ≤ 20

32 (5.8)

9 (2.1)

26 (5.7)

 21–25

156 (28.8)

58 (13.6)

138 (30.2)

 26–30

360 (65.7)

199 (46.8)

293 (64.1)

 ≥ 31

0 (0)

157 (36.9)

0 (0)

Age difference (years) with partner

 0–4

392 (71.5)

NA

326 (71.3)

 5–9

96 (17.5)

84 (18.4)

 ≥ 10

33 (6.0)

27 (5.9)

Migration background

 Western

412 (75.2)

333 (78.4)

345 (75.5)

 Non-Western

119 (21.7)

78 (18.4)

100 (21.9)

Highest level education

 High

272 (49.6)

192 (45.2)

222 (48.6)

 Middle

225 (41.1)

181 (42.6)

196 (42.9)

 Low

34 (6.2)

37 (8.7)

27 (5.9)

Socioeconomic status (SES)

 Very high and high SES

117 (21.4)

NA

95 (20.8)

 Average SES

211 (38.5)

183 (40.0)

 Low and very low SES

197 (35.9)

164 (35.9)

Urbanity

 Very high urbanity

103 (18.8)

NA

83 (18.4)

 High urbanity

252 (46.0)

215 (47.0)

 Average to low urbanity

173 (31.6)

146 (31.9)

Province

 Noord-Holland

198 (36.1)

NA

173 (37.9)

 Zuid-Holland

120 (21.9)

89 (19.5)

 Other

210 (38.3)

183 (40.0)

Marital status

 Married or living together

460 (83.9)

NA

388 (84.9)

 Single or partner not living together

70 (12.8)

56 (12.3)

Duration relationship (years)

 0–4

193 (35.2)

NA

162 (35.4)

 5–9

221 (40.3)

185 (40.5)

 ≥ 10

84 (15.3)

70 (15.3)

Religion

 No

330 (60.2)

278 (65.4)

276 (60.4)

 Yes, Catholic/Christian

169 (30.8)

104 (24.5)

142 (31.1)

 Yes, Islamic

27 (4.9)

15 (3.5)

23 (5.0)

 Yes, else

1 (0.2)

6 (1.4)

1 (0.2)

Partner (distant) relative

No

501 (91.4)

NA

420 (91.9)

 Yes

4 (0.7)

4 (0.9)

Migration background partner

 Western

394 (71.9)

NA

331 (72.4)

 Non-Western

114 (20.8)

95 (20.8)

Highest level education partner

 High

230 (42.0)

NA

185 (40.0)

 Low/middle

280 (51.1)

242 (53.0)

Pregnancy information

Pregnancy planned and desired

 Planned and desired

385 (70.3)

NA

327 (71.6)

 Not planned, but desired

145 (26.5)

118 (25.8)

Gestational age at discovery (weeks)

 0–4

243 (44.3)

NA

196 (42.9)

 5–9

266 (48.5)

233 (51.0)

 ≥ 10

17 (3.1)

12 (2.6)

Gestational age at study inclusion

 1st trimester (1–12 weeks)

168 (30.7)

NA

143 (31.3)

 2nd trimester (13–27 weeks)

242 (44.2)

201 (44.0)

 3rd trimester (28–41 weeks)

115 (21.0)

97 (21.2)

BMI (pre-pregnancy, kg/m²)

 < 18.5

30 (5.5)

NA

25 (5.5)

 18.5–25

354 (64.6)

292 (63.9)

 25–30

94 (17.2)

83 (18.2)

 ≥ 30

40 (7.3)

34 (7.4)

Antibiotics < 3 months

 Yes

45 (8.2)

27 (6.4)

35 (7.7)

 No

475 (86.7)

371 (87.3)

401 (87.7)

Gravity

 0

302 (55.1)

NA

242 (53.0)

 1

154 (28.1)

136 (29.8)

 2 or more

73 (13.3)

65 (14.2)

Parity

 0

362 (66.1)

NA

296 (64.8)

 1

130 (23.7)

114 (24.9)

 2 or more

20 (3.6)

18 (3.9)

Miscarriage

 No

425 (77.6)

NA

351 (76.8)

 Yes

81 (14.8)

71 (15.5)

Abortion

 No

172 (31.4)

NA

151 (33.0)

 Yes

50 (9.1)

46 (10.1)

Complication(s) previous newborn

NA

 No

531 (96.9)

442 (96.7)

 Yes

17 (3.1)

15 (3.3)

Behavioural risk factors

Age at sexual debut (years)

 < 18

354 (64.6)

215 (50.6)

301 (65.9)

 ≥ 18

146 (26.6)

151 (35.5)

120 (26.3)

No. of sex partners in last 12 months

 0–1 partner

492 (89.8)

377 (88.7)

415 (90.8)

 2 or more

24 (4.4)

13 (3.1)

19 (4.2)

New sex partner in last 3 months

 No

521 (95.1)

398 (93.6)

438 (95.8)

 Yes

7 (1.3)

2 (0.5)

6 (1.3)

Condom use at start current relation

 Always/mostly to regular

326 (59.5)

246 (57.9)

274 (60.0)

 Not always to never

191 (34.9)

147 (34.6)

159 (34.8)

STI-related symptoms

 0

217 (39.6)

374 (88.0)

180 (39.4)

 1

171 (31.2)

24 (5.6)

145 (31.7)

 2

100 (18.2)

2 (0.5)

87 (19.0)

 3 or more

42 (7.7)

0 (0.0)

33 (7.2)

Previous STI test

 No

237 (43.2)

248 (58.4)

202 (44.2)

 Yes

289 (52.7)

149 (35.1)

238 (52.1)

   History of STI

83 (28.7)

45 (30.2)

71 (29.8)

   No history of STI

198 (68.5)

101 (67.8)

161 (67.6)

Smoking

 No, never

202 (36.9)

124 (29.2)

173 (37.9)

 In the past, not during pregnancy

208 (38.0)

169 (39.8)

169 (37.0)

 Yes, during pregnancy

120 (21.9)

108 (25.4)

102 (22.3)

  Yes, stopped since pregnant

77 (14.1)

13 (3.1)

65 (14.2)

  Yes, during pregnancy

43 (7.8)

95 (22.4)

37 (8.1)

Alcohol

 No, never

51 (9.3)

NA

41 (9.0)

 In the past, not during pregnancy

111 (20.3)

96 (21.0)

 Yes, during pregnancy

365 (66.6)

305 (69.0)

  Yes, stopped since pregnant

354 (64.6)

294 (64.4)

  Yes, continued since pregnancy

11 (2.0)

11 (2.4)

Drugs

 No, never

343 (62.6)

217 (51.1)

293 (64.1)

 In the past, not during pregnancy

162 (29.6)

134 (31.5)

132 (28.9)

  Soft drugs only

111 (68.5)

81 (60.4)

90 (68.2)

  Hard drugs ± soft drugs

49 (30.2)

51 (38.1)

40 (30.3)

 Yes, during pregnancy

23 (4.2)

47 (11.1)

17 (3.7)

  Soft drugs only

17 (73.9)

22 (55.0)

13 (76.5)

  Hard drugs (or both)

6 (26.1)

18 (45.0)

4 (23.5)

  Yes, stopped since pregnant

22 (4.0)

7 (1.6)

17 (3.7)

  Yes, continued since pregnant

1 (0.2)

40 (9.4)

0 (0.0)

STIs (95% CI)

13 (2.4, 1.3–4.0)

10 (2.2, 1.0–4.0)

11 (2.4, 1.2–4.3)

 Chlamydia

10 (1.8, 0.9–3.3)

10 (2.2, 1.0–4.0)

9 (2.0, 0.9–3.7)

 Gonorrhoea

2 (0.4, 0.0–1.3)

1 (0.2, 0.0–1.3)

1 (0.2, 0.0–1.2)

 Trichomoniasis

2 (0.4, 0.0–1.3)

0 (0.0, 0.0–0.9)

1 (0.2, 0.0–1.2)

 More than 1 STI

1 (0.2, 0.0–1.2)

1 (0.2, 0.0–1.3)

0 (0.0, 0.0–0.9)

CT knowledge

CT knowledge score (median, IQR)

9.0 (8.0–11.0)

9.0 (7.0–10.0)

9.0 (7.0–11.0)

 0–5 points (low score)

59 (10.8)

65 (15.3)

54 (11.8)

 6–9 points (middle score)

221 (40.3)

184 (43.3)

181 (39.6)

 10–12 points (high score)

249 (45.4)

153 (36.0)

209 (45.7)

Pregnancy outcomes

Adverse perinatal outcome

 No

397 (72.4)

397 (86.9)

 Yes

50 (9.1)

50 (10.9)

Prematurity (< 37 weeks)

 No

417 (76.1)

417 (91.2)

 Yes

32 (5.8)

32 (7.0)

Premature rupture of membranes

 No

433 (79.0)

433 (94.7)

 Yes

18 (3.3)

18 (3.9)

Low birthweight (< 2500 g)

 No

426 (77.7)

426 (93.2)

 Yes

19 (3.5)

19 (4.2)

Small for gestational age

 No

418 (76.3)

418 (91.5)

 Yes

28 (5.1)

28 (6.1)