Contribution of Syphilis to Adverse Pregnancy Outcomes in People Living With and Without HIV in South Brazil: 2008 to 2018

Background: Syphilis coinfection among pregnant people living with HIV (PLH) may worsen pregnancy outcomes. We evaluated the impact of syphilis coinfection on pregnancies in south Brazil. Methods: Data were extracted from hospital records between January 1, 2008, and December 31, 2018. Preterm birth (PTB), low birth weight (LBW <2500 g), and a composite adverse infant outcome (AIO: HIV vertical transmission, loss to follow-up before HIV diagnosis, stillbirth, congenital syphilis) were evaluated among pregnancies without HIVand syphilis (PWOH + S), PLH monoinfection, syphilis monoinfection (PLS), and PLH with syphilis (PLH + S). Results: Among 48,685 deliveries where patients were tested for HIVand syphilis, 1353 (2.8%) occurred in PLH; of these, 181 (13.4%) were HIV/ syphilis coinfected (PLH + S). Among PLH, 2.4% of infants acquired HIV and 13.1% were lost to follow-up before HIV diagnosis. Among all PLS, 70.5% of infants acquired congenital syphilis. Across the cohort, 1.2% stillbirths/neonatal deaths occurred. Thirty-seven percent of PLH + S did not initiate antiretroviral therapy versus 15.4% of PLH monoinfection (P < 0.001). Less than half (37.6%) of PLH + S had VDRL titers ≥1:16 compared with 21.7% of PLS only (P < 0.001). Among PLH, syphilis coinfection and unknown/high VDRL titers (≥1:16) increased AIO risk more (adjusted relative risk [aRR], 3.96; 95% confidence interval [CI], 3.33–4.70) compared with low VDRL titers (≤1:8; aRR, 3.51; 95% CI, 2.90–4.25). Unsuppressed viremia (≥50 copies/mL) was associated with risk of PTB (aRR, 1.43; 95% CI, 1.07–1.92) and AIO (aRR, 1.38; 95% CI, 1.11–1.70) but not LBW. Lack of prenatal care was significant in predicting PTB and LBW in all PLH and PLS monoinfection. Conclusions: Syphilis coinfection worsens AIOs in all women and compounds negative effects of HIV infection during pregnancy. Effective syphilis treatment and HIV viral load suppression are paramount for optimal obstetric care.