Syphilis is a systemic disease caused by the spirochete Treponema pallidum.1 Syphilis can be transmitted vertically from mother to child. The most common mode of vertical transmission is through the placenta; however, transmission can occur during delivery if maternal genital lesions are present.2 In pregnant women, syphilis can lead to spontaneous abortion, stillbirth, prematurity, and a wide spectrum of clinical manifestations in live-born infants.2–4 US surveillance data demonstrates that congenital syphilis cases are increasing. The 2013 rate of congenital syphilis (9.1 cases per 100,000 live births) marked the first increase in congenital syphilis since 2008 and during 2013–2014, the rate continued to increase. There were 458 cases of congenital syphilis reported in 2014 compared with 359 in 2013.5,6
Prenatal syphilis screening is an important step in preventing congenital syphilis infection. The Centers for Disease Control and Prevention, American College of Obstetricians and Gynecologists, and the US Preventive Services Task Force recommend all pregnant women, regardless of risk, be screened early in pregnancy for syphilis.7–9 Most states mandate syphilis screening at the first prenatal visit for all women. Third trimester screening, once at 28 to 32 weeks gestation and again at delivery is recommended for women at high risk of infection.9
We conducted an analysis of over 300,000 commercially insured pregnant women to determine syphilis screening rates at different prenatal stages and if this varied by state prevalence of congenital syphilis. In addition, we sought to assess adverse birth outcomes among pregnant women with and without a prenatal syphilis test at least 1 month before delivery.
We performed a descriptive analysis using administrative data from 2013 in the Truven Health MarketScan databases. This large commercial claims database includes approximately 50 million enrollees in more than 100 US health plans.10 MarketScan includes both enrollees who receive insurance through their employers and individuals who purchase their own commercial insurance. The billing claims data were submitted electronically to Truven once they were nearly 100% complete, and Truven then performs several validation steps. This study was determined to be exempt from the Centers for Disease Control and Prevention institutional review board because MarketScan data does not contain personally identifying information.
We used procedural and diagnostic codes to identify women aged 15–44 years with a live birth in 2013 who were continuously enrolled in health plans at least 210 days before the date of delivery. A previous study has used the enrollment 210 days before the date of delivery rather than the enrollment 280 days during the entire pregnancy to include more pregnant women who had adequate prenatal care to assess prenatal health care services.11 We identified pregnant women and their delivery dates using Current Procedural Terminology (CPT) and International Classification of Disease, 9th Revision, Clinical Modification codes(ICD-9).11,12 Screening among pregnant women was assessed at a number of timepoints1: first trimester, 0–12 weeks gestation2; third trimester, 28–40 weeks gestation; and3 week of delivery. We also assessed syphilis screening at 0–27 weeks, 0–40 weeks (before delivery) and at least once during pregnancy (any stage). We used CPT codes to identify testing for syphilis during the prenatal period and defined prenatal laboratory tests as those completed 293 days before and on the date of delivery. This period encompassed the average 40-week gestational period of a term pregnancy but also included laboratory tests that were completed up to 42 weeks of gestation to include late-term pregnancies. The date of the first prenatal visit was defined as the earliest date that the pregnant woman had a claim for prenatal visit. Syphilis tests provided during the pregnancy or on the day of delivery were identified by the CPT codes for: syphilis (80055, 86592, 86593, 86781, or 86780).
Congenital syphilis was defined as a newborn diagnosed with ICD-9 code of 090. Stillbirth was defined as a birth outcome with ICD-9 code of 779.9, V27.1, V27.4, or V27.7. We used the 2013 Sexually Transmitted Diseases Surveillance report to categorize states as low, medium, and high congenital syphilis burden states. States with high congenital syphilis rates (> Healthy People goal of 9.1 congenital syphilis (CS) cases per 100,000 live births) in 2013: Arkansas, Arizona, California, Florida, Georgia, Illinois, Louisiana, Maryland, Ohio, and Texas. States with medium congenital syphilis rates (state had at least one CS, but the number CS cases per 100,000 births ≤ Healthy People goal of 9.1) in 2013: Alabama, Arkansas, Delaware, Kentucky, Massachusetts, Michigan, Missouri, North Carolina, New Mexico, Nevada, New York, Pennsylvania, South Carolina, Tennessee, and Virginia. States with low congenital syphilis rates (zero cases of CS) in 2013: Colorado, Connecticut, Hawaii, Iowa, Idaho, Indiana, Kansas, Maine, Minnesota, Mississippi, Montana, Nebraska, New Hampshire, New Jersey, North Dakota, Oklahoma, Oregon, Rhode Island, South Dakota, Utah, Vermont, Washington, West Virginia, Wisconsin, and Wyoming. All analyses were conducted using SAS 9.3. We did not report p values on statistical comparisons of estimates due to the large sample sizes, according to the recent American Statistical Association statement on statistical significance and p value.13
A total of 338,854 commercially insured pregnant women with a birth in 2013 were included in this analysis; 288,324 (85%) had a syphilis test performed at least once during the prenatal period (Table 1). Pregnant women in the South were more likely to receive a prenatal syphilis test compared with women in all other regions, particularly the Northeast (87 % vs 79%). Syphilis testing rates were approximately 80% during the first trimester, 20% in the third trimester, and 8% in the week of delivery (Table 2). Compared with women in states with low congenital syphilis rates, women in states with high congenital syphilis rates were more likely to receive a syphilis test in the third trimester (25% vs 14.7%) and the week of delivery (14% vs 2.6%). Congenital syphilis was a rare occurrence in this population; 6 CS cases occurred among pregnant women who had prenatal syphilis testing at least 1 month before delivery, and 1 CS case occurred among pregnant women who were not tested at least 1 month before delivery. The stillbirth rate was higher among women without prenatal testing one month before delivery (0.66%) compared to women with a syphilis test 1 month before delivery (0.45%).
Prenatal syphilis screening is a key step in identifying women with syphilis to initiate timely treatment and prevent adverse pregnancy outcomes and transmission of syphilis infection to neonates. Our study found that in a commercially insured population, only 85% received at least 1 syphilis test during the prenatal period.
Syphilis screening during the third trimester was low; third trimester screening was considerably higher in high congenital syphilis states compared with low congenital syphilis states. States with a heavy burden of infectious syphilis in women tend to require more prenatal testing, and 12 states have laws that require third-trimester testing for all or high-risk women.14 Unfortunately, 1 in 4 states with high rates of syphilis do not mandate third-trimester screening.15 Low syphilis testing during the third trimester or on the date of delivery among all pregnant women, especially among pregnant women residing in states with high or medium congenital syphilis rates, leaves a critical gap in the prevention of congenital syphilis infection. Reasons for lower rates of screening in the third trimester may include patient refusal or provider apathy due to assumed rarity of syphilis infection in their community.16 Interventions should be developed to increase prenatal syphilis testing as recommended. One study found that almost 90% of obstetric medical providers reported third-trimester syphilis screening after a local board order issued to increase prenatal syphilis screening.17 This public health guidance is an intervention that could be considered in other local communities and states with high congenital syphilis rates. Although a recent study found that nationally, universal third trimester screening was not cost-effective, individual high-risk communities should evaluate the syphilis incidence in their population and implement a program of routine syphilis rescreening.15
The frequency of fetal loss or stillbirth is estimated to be 21% higher among women with syphilis compared to women without syphilis.18 In our study, the stillbirth rate was higher among women without prenatal testing one month before delivery compared with women with a late prenatal syphilis test, the cause of stillbirth was not captured in this study.
Our study has several limitations. First, prenatal screening rates may have been underestimated because of inaccurate or incomplete administrative coding. Second, our findings may not be generalizable because MarketScan databases are a convenience sample of women with commercial insurance and may not be representative of all US women. Third, a small number of women in MarketScan may have changed insurance carriers after the first trimester, and any prenatal screening during that period would not have been captured. Fourth, although many CS cases might be concentrated in certain areas in a given state, we were not able to explore geographic areas smaller than the state level in this analysis, Finally, CS cases used in this study were based on ICD-9 diagnosis that might not be confirmed CS cases.
In summary, pregnant women in this population had suboptimal rates of syphilis screening during the prenatal period. Congenital syphilis was a relatively rare event but stillbirths did occur in this population. All women in our study had commercial insurance and received prenatal care; however, third trimester syphilis screening was low. Identification of barriers to screening including health provider, patient and policy-level factors is needed to assist development of structural interventions that improve screening and reduce adverse pregnancy outcomes due to syphilis.
1. Holmes K. Sexually Transmitted Diseases. 2008;4th Edition.
2. Wolff T, Shelton E, Sessions C, et al. Screening for syphilis infection in pregnant women: evidence for the U.S. Preventive Services Task Force reaffirmation recommendation statement. Ann Intern Med 2009; 150:710–716.
3. Chakraborty R, Luck S. Syphilis is on the increase: the implications for child health. Arch Dis Child 2008; 93:105–109.
4. Fowler CI, Gavin NI, Adams EK, et al. Racial and ethnic disparities in prenatal syphilis screening among women with Medicaid-covered deliveries in Florida. Matern Child Health J 2008; 12:378–393.
5. Centers for Disease Control and Prevention. Sexually Transmitted Disease Surveillance 2014. Atlanta: U.S. Department of Health and Human Services; 2015.
6. CDC. Increase in Incidence of Congenital Syphilis—United States, 2012–2014. MMWR Morb Mortal Wkly Rep 2015; 64:1241–1245.
7. Guidelines for perinatal care, 7th ed. Washington, DC: American College of Obstetricians and Gynecologists and American Academy of Pediatrics; 2012.
8. Meyers D, Wolff T, Gregory K, et al. USPSTF recommendations for STI screening. Am Fam Physician 2008; 77:819–824.
9. Workowski KA, Bolan GA. Centers for Disease C, Prevention. Sexually transmitted diseases treatment guidelines, 2015. MMWR Recomm Rep 2015; 64(RR-03):1–137.
10. Hawkes S, Matin N, Broutet N, et al. Effectiveness of interventions to improve screening for syphilis in pregnancy: a systematic review and meta-analysis. Lancet Infect Dis 2011; 6:684–691.
11. Ross CE, Tao G, Patton M, et al. Screening for human immunodeficiency virus and other sexually transmitted diseases among U.S. women with prenatal care. Obstet Gynecol 2015; 125:1211–1216.
12. Tao G, Patterson E, Lee LM, et al. Estimating prenatal syphilis and HIV screening rates for commercially insured women. Am J Prev Med 2005; 28:175–181.
13. The ASA's Statement on p-Values: Context, Process, and Purpose. The American Statistician, 70, p.129-.
14. Hollier LM, Hill J, Sheffield JS, et al. State laws regarding prenatal syphilis screening in the United States. Am J Obstet Gynecol 2003; 189:1178–1183.
15. Albright CM, Emerson JB, Werner EF, et al. Third-trimester prenatal syphilis screening: a cost-effectiveness analysis. Obstet Gynecol 2015; 126:479–485.
16. Edwards RK, Bennett M, Langstraat C, et al. Assessment of the value of rescreening for syphilis in the third trimester of pregnancy. Infect Dis Obstet Gynecol 2006;2006:56504.
17. Collier MG, Taylor MM, Winscott MM, et al. Assessing compliance with a county board order for third trimester syphilis screening in Maricopa County, Arizona. Sex Reprod Healthc 2011; 2:125–128.
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18. Gomez GB, Kamb ML, Newman LM, et al. Untreated maternal syphilis and adverse outcomes of pregnancy: a systematic review and meta-analysis. Bull World Health Organ 2013; 91:217–226.