Table 3

Factors associated with STI incidence in pregnant women in South Africa (2016–2018)

Any STI, n (%)No STI, n (%)IRR (95% CI)
Total21 (5)398 (95)
Sociodemographic characteristics
Maternal age (years), median (IQR)30 (25–33)30 (26–34) 0.96 (0.89 to 0.98)
GA at first ANC (weeks), median (IQR)17 (15–26)18 (13–23)1.01 (0.95 to 1.08)
Education level completed
 Primary9 (43)134 (34)Ref
 Secondary9 (43)248 (62)0.55 (0.22 to 1.40)
 Tertiary (college/university)3 (14)16 (4)2.50 (0.68 to 9.26)
Relationship with father of child
 Married/cohabitating12 (57)219 (55)Ref
 Not married/non-cohabitating7 (33)169 (42)1.00 (0.43 to 2.30)
 No relationship2 (10)10 (3)
Employment status
 Formal employment8 (38)149 (37)Ref
 Informal employment0 (0)12 (3)0.55 (0.22 to 1.40)
 Unemployed/attending school13 (62)237 (60)2.50 (0.68 to 9.26)
Site
 Cape Town5 (24)159 (40)Ref
 Tshwane District16 (76)239 (60)2.05 (0.76 to 5.51)
Clinical characteristics in this pregnancy
HIV status
 Positive17 (81)304 (76)1.29 (0.44 to 3.77)
 Negative4 (19)94 (24)Ref
Sexual behaviour during pregnancy
 Vaginal sex17 (81)359 (90)0.48 (0.17 to 1.38)
 Oral sex2 (10)23 (6)1.66 (0.41 to 6.73)
 Anal sex1 (5)10 (3)1.85 (0.27 to 12.6)
 2+ sex partners in the past 3 months0 (0)12 (3)
Suspect partner of having another sex partner
 No7 (33)194 (49)Ref
 Yes8 (38)126 (31)1.71 (0.63 to 4.62)
 Don’t know5 (24)77 (19)1.75 (0.57 to 5.36)
 N/A*1 (5)1 (1) 14.3 (2.99 to 68.8)
Partner’s serostatus
 Concordant HIV-negative2 (10)65 (16)Ref
 Concordant HIV-positive2 (10)72 (18)0.90 (0.13 to 6.42)
 Serodiscordant2 (10)62 (16)1.04 (0.14 to 7.43)
 Serostatus unknown15 (70)199 (50)2.34 (0.53 to 10.26)
  • Confidence intervals in bold had sufficient evidence to conclude that the groups were statistically significantly different

  • *Refers to women who did not have a partner; they were not in a relationship.

  • ANC, antenatal clinic; GA, gestational age; IRR, incidence rate ratio; n, number of participants; N/A, not applicable; ref, reference.