Repeat prenatal syphilis screening increased after universal testing law

Repeat prenatal syphilis screening increased among pregnant Medicaid enrollees in Michigan following implementation of a 2018 law requiring universal opt-out testing in the first and third trimesters, according to a study published in Pregnancy. The analysis found substantial gains in early third-trimester screening between 2017 and 2023, although improvements were less pronounced in counties with the highest syphilis burden.¹

Background

Congenital syphilis is a preventable but potentially devastating condition caused by vertical transmission of Treponema pallidum during pregnancy. Untreated infection can result in miscarriage, stillbirth, neonatal death, or severe long-term morbidity, including hepatosplenomegaly, anemia, bone abnormalities, seizures, and neurodevelopmental delay. Nearly all cases can be prevented with timely maternal diagnosis and adequate treatment initiated at least 30 days before delivery.

In Michigan, rates of primary and secondary syphilis among women increased more than fourfold from 2017 to 2023, rising from 0.7 to 3.6 per 100,000 population. During the same period, the reported rate of congenital syphilis increased from 9.0 to 53.8 per 100,000 live births. Similar increases were observed nationally, with primary and secondary syphilis among women rising from 2.3 to 8.1 and congenital syphilis increasing from 24.4 to 105.8.

To strengthen prevention efforts, Michigan enacted legislation in December 2018 requiring universal opt-out syphilis testing of pregnant women in both the first and third trimesters, with additional screening at delivery if prenatal testing was missed. State guidance specifies third-trimester screening at 28–32 weeks’ gestation.

Because Medicaid pays for approximately 2 of every 5 births in Michigan and women with Medicaid-funded deliveries have a higher risk of syphilis diagnosis at delivery, the Medicaid population provides a stable sentinel group for evaluating screening trends over time.

The researchers analyzed de-identified health claims data from women enrolled in Michigan Medicaid who delivered an infant between 2017 and 2023. Timing of syphilis screening was estimated by subtracting the screening date from the delivery date.

They calculated the percentage of pregnant women who were:

• ever screened during pregnancy (280–0 days preceding delivery),
• screened during the first or second trimesters (280–94 days preceding delivery),
• screened in the early third trimester (93–30 days preceding delivery),
• screened in both early pregnancy and the early third trimester, and
• screened less than 30 days before delivery.

Screening patterns in 2017 were compared with those in 2023, 5 years after the legislation took effect. Absolute percentage changes were examined overall and by demographic characteristics, including residence in counties with elevated syphilis rates.

Key findings

Across the seven-year study period, 211,289 deliveries were evaluated. Approximately half of the women were Non-Hispanic White, half were younger than 27 years, and three-quarters lived in counties with elevated syphilis rates.

Screening for syphilis at least once during pregnancy was common, averaging 92.0%, and remained stable before and after the legislation (−1.8%). Screening during the first or second trimester was also common at 82.3% and showed a modest decline (−4.0%). Screening performed only within 30 days of delivery was infrequent at 8.9% and increased slightly (+1.8%).

In contrast, screening during the early third trimester increased substantially after the law took effect, rising from 37.1% in 2017 to 53.7% in 2023. Screening both in the first or second trimester and again in the early third trimester also increased, from 30.1% to 45.0%.

Improvements in repeat screening were smaller in counties with higher syphilis burden compared with lower-burden areas. Patterns were otherwise similar across age and race or ethnicity subgroups.

Implications

The findings suggest that legislation mandating universal first- and third-trimester syphilis testing was associated with meaningful increases in repeat prenatal screening, particularly in the early third trimester. However, persistent gaps in high-burden counties indicate that additional strategies are needed to ensure consistent implementation where the risk of congenital syphilis is greatest.

The authors emphasize the importance of continued efforts to raise awareness among providers and patients about the necessity and value of repeat syphilis testing during pregnancy to further strengthen congenital syphilis prevention.

Reference:

Diesel, J.C. and Macomber, K. (2026), Modest improvement in universal prenatal syphilis screening 5 years after legislation enacted. Pregnancy. doi.org/10.1002/pmf2.70219