Screening During Pregnancy Reduces the Incidence of Congenital Syphilis

Syphilis infection during pregnancy can lead to miscarriage, stillbirth, or birth defects in children. Because of this, the US Preventative Services Task Force recommends early screening for syphilis in all pregnant women.

“There is convincing evidence that the benefits of early detection and treatment of syphilis in pregnant women are substantial, namely curing the infection and preventing harmful pregnancy outcomes including fetal and neonatal death,” the authors of the recommendations wrote in the article published in JAMA. “Treatment earlier in pregnancy is more effective than later; therefore, screening is recommended early in pregnancy.”

In a new literature review, also published in JAMA, a team of investigators from Kaiser Permanente, set out to assess available data on the effectiveness and harms of syphilis screening during pregnancy along with the harms of penicillin treatment during pregnancy in order to inform the US Preventative Services Task Force.

Data selected from MEDLINE, PubMed, and the Cochrane Central Register of Controlled Trials which were reviewed by 2 investigators. Ultimately, 7 studies in 8 publications were included in the review.

In a study that featured data from Shenzhen, China, investigators sought to understand if screening pregnant women for syphilis can reduce the incidence of congenital syphilis in newborns.

Between 2002 and 2012, 2,442,237 pregnant women were offered syphilis screening through nontreponemal testing with reflex to treponemal testing if the test was positive. From the total population, 8455 pregnant women tested positive for syphilis. Although the timing of screening pregnant women had not been reported, investigators noted that the mean gestational week in which treatment occurred was 26.5 weeks.

During the same time period, screening for syphilis in pregnant women increased from 89.8% to 97.2% and the incidence of congenital syphilis decreased from 109.3 to 9.4 cases per 100,000 live births. Additionally, the incidence of all adverse outcomes in pregnant women with syphilis declined from 42.7% to 19.2%; incidence of congenital syphilis declined from 11.7% to 3.2%.

To determine the harms of syphilis screening during pregnancy, the investigators analyzed 5 studies with a total of 21,795 participants which evaluated the false-positive results of treponemal tests, 1 of which also reported on false-negative results.

One of the studies, which included 139 participants, evaluated the prozone phenomenon—which is a false-negative response from high antibody titer—with rapid plasma regain testing using undiluted samples (2.9%).

Investigators also included 1 new study in their analysis, consisting of 318 participants, which evaluated the false-negative findings of the nontreponemal tests. These studies found that false-positives with treponemal-specific enzyme or chemiluminescent immunoassays were common (46.5% to 88.2%), therefore, warranting reflexive testing for all positive test findings.

No studies examining the harm of syphilis treatment with penicillin during pregnancy were identified, according to the authors.

Some limitations of this study are based upon the fact that the investigators were only searching for studies related to the recommendations in the United States. Therefore, the review does not include studies addressing the effectiveness of screening or early prenatal care in low- or middle-income countries, because the studies were less applicable in the United States. Additionally, the investigators did not address the efficacy of alternative antibiotic treatments for syphilis in pregnant women, such as ceftriaxone.

The findings of the literature review reinforce the recommendations of the US Preventative Services Task Force. Syphilis screening in pregnant women is associated with reduced incidence of congenital syphilis and available evidence supports the need for reflexive testing for positive results.