Background
Understanding the prevalence, risk factors, and barriers to treatment of syphilis in pregnant women is essential to inform the prevention of vertical transmission.
Methods
Within a clinical trial of PrEP promotion interventions, we enrolled 750 HIV-negative pregnant women aged >16 years and used medical records to examine syphilis testing and treatment. We report the prevalence of prior syphilis (TPHA+/RPR-) and active syphilis (TPHA+/RPR+), along with the proportion of those who received complete treatment (3 doses of benzathine penicillin per local guidance). We used logistic regression to identify factors associated with active syphilis and incomplete treatment.
Results
In 750 participants (median age 26y, median gestational age 29w, IQR 23–35), 57% (n=424) were already on PrEP and 43% (n=326) initiated PrEP. The overall prevalence of syphilis was 11% (n=84), with 6% (n=45) prior syphilis infections and 5% (n=39) active syphilis of which 56% of women had RPR titres ≥ 1:8. Women who were <25 years had 2.6 times the odds of active syphilis compared to older women (OR = 2.59, 95% CI: 1.33–5.29). Alcohol use in pregnancy was associated with a doubling in the odds of active syphilis (aOR=2.00, 1.04–3.88) compared to women who did not report alcohol use. 55% (n=16) of women with active syphilis did not receive complete treatment, while a total of 35% (n=29) of women with prior and active syphilis underwent complete treatment. For each additional year of maternal age, the odds of incomplete treatment increased by 10% (OR=1.10, 1.03–1.19). Women who were unmarried/not co-habiting had 3.9 times the odds of incomplete treatment (aOR=3.86, 1.10–15.8) compared to. Sexual activity during pregnancy was associated with incomplete treatment (aOR=4.78, 1.14–25.3). The mean gestational age of participants’ first positive syphilis test result during pregnancy was at 22 weeks (IQR 16–28); 6% (n=5) of syphilis was detected ≤4 weeks prior to delivery and 3 infants were diagnosed with congenital syphilis.
Conclusions
Syphilis is prevalent among pregnant women using oral PrEP. Identifying risk factors for incomplete syphilis treatment during pregnancy is essential for targeted interventions for timely syphilis detection and treatment, ultimately reducing the risk of adverse pregnancy outcomes.