Prenatal Care, Universal Syphilis Screening Critical for US Women

A team of investigators hypothesized that prevalent syphilis infection in women with and without HIV may be a way to identify individuals who are at an elevated risk of a stillbirth over time.

Syphilis cases have been on the rise among women in the United States since 2013. In fact, congenital syphilis rates are at a 20-year high. This is concerning, as syphilis infection during pregnancy can result in a stillbirth.

A team of investigators, led by individuals from the University of Alabama at Birmingham, hypothesized that prevalent syphilis infection in women with and without HIV may be a way to identify individuals who are at an elevated risk of a stillbirth over time.

"We have been following a cohort of HIV-infected or at-risk women for many years. Since syphilis is re-emerging, but still relatively rare, this cohort provided an opportunity to assess the impact of still birth among women expected to have high syphilis rates," study author Kristal Aaron, DrPH, MSPH, Clinical Data Manager at The University of Alabama at Birmingham, told Contagion®.

The study team reported on their investigation in a poster session at the Conference on Retroviruses and Opportunistic Infections (CROI 2020).

The investigators used data collected in the multisite US Women’s Interagency HIV Study between 1994 and 2016. The data featured documented syphilis testing and pregnancy outcomes for women aged 16 through 49 years. In total, 3577 women were included, 2687 (75%) of whom were living with HIV and 879 women (25%) who did not have HIV.

The mean age at enrollment was 36 years and prevalent syphilis—defined as a positive RPR screen with confirmatory treponemal antibody testing at baseline—was more common in women with HIV compared with women without HIV (8% vs 4%, P <0.05).

In the study, history of stillbirth and stillbirth during follow up were examined separately.

Birth outcomes were self-reported, with 4.6% reporting stillbirth during the study period and 2.2% of women who were pregnant during follow-up reporting a stillbirth. During follow-up, 4.7% of women with prevalent syphilis had a stillbirth compared to 2.0% of syphilis seronegative women.

The investigators used logistic regression with backward selection to create adjusted models using HIV status, prevalent syphilis and preselected covariates. Information on drug use, alcohol intake, and sex was collected at biannual visits.

“Predictors of stillbirth in the unadjusted model (P<0.2) included syphilis at baseline, HIV-negative status, black race, non-heterosexual identity, income <$12,000, HCV, older age, lifetime sexual partners, and younger age of sexual debut,” the study authors wrote in their abstract.

Additionally, in multivariable models, prior stillbirth was associated with syphilis at baseline (OR 1.7, 95% CI 1.0—3.0), HIV-negative status (OR 1.6, CI 1.1–2.2), older age (OR 1.0, 95% CI 1.0–1.1) and younger age at sexual debut (OR 0.95, 95% CI 0.9–-0.99).

In the study, the investigators found that reported stillbirth rates were 4 times higher compared with the general US population. The team also observed that women with prevalent syphilis had higher rates of prior stillbirth and stillbirth during follow-up.

"We are continuing to build on this work by obtaining additional data to examine historical stillbirth and other pregnancy outcomes among women living with or at risk of HIV infection," Aaron said.

“Women with syphilis are at elevated risk of prior stillbirth in this cohort of women. Early prenatal care and universal syphilis screening is critical for US women living with HIV or at risk of HIV infection.”

The abstract, Stillbirth and prevalent syphilis in the US women’s interagency HIV study, 1994-2016, was presented on Monday, March 9, 2020 in a virtual session of CROI 2020.