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The Real World of STD Prevention

Declining Chlamydia and Gonorrhea Diagnoses Among Pregnant Women in South Carolina, 2008 to 2018

Lazenby, Gweneth B. MD, MSCR; Savage, Ashlyn H. MD, MSCR; Horner, Gwynneth MD; Richmond, Joshua BS; Peterman, Thomas A. MD, MSc

Author Information
Sexually Transmitted Diseases: March 2021 - Volume 48 - Issue 3 - p 141-144
doi: 10.1097/OLQ.0000000000001297
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Chlamydia trachomatis and Neisseria gonorrhoeae are the most common reportable sexually transmitted infections (STIs) in the United States.1 Chlamydial and gonococcal infections are often asymptomatic, but if left untreated, they can progress to pelvic inflammatory disease, which is associated with infertility and ectopic pregnancy.2,3 Both chlamydia and gonorrhea are associated with an increased risk of pregnancy complications and congenital infection.4 Reported cases of chlamydia in the United States have increased nearly every year since it first became reportable, but trends in prevalence remain elusive because only positive laboratory test results are reported.1 Without negative laboratory test results for comparison, it is unclear if changes in reported cases represent changes in testing or changes in prevalence among those tested. Accurate trend information would be helpful in evaluating the impact of national control efforts. Trends in nationally representative samples of women in the United States have suggested that prevalence is declining or remaining stable despite increases in reported cases.5 However, these estimates are imprecise because of the small number of women included in these studies.

Trends in sentinel populations can help interpret trends in national case report data. Good sentinel populations are those where infection is likely to be found, testing is not based on symptoms, and a large and consistent fraction of the population is tested.6 The National Job Training Program serves as a source for sentinel screening for chlamydia and gonorrhea.7,8 Since 2010, in that population, chlamydia positivity increased slightly among young White women and remained stable among young Black women, whereas gonorrhea positivity increased slightly in all subgroups of young women.8,9 We believe pregnant women are an excellent sentinel population to study trends in STIs because nearly all are screened for disease regardless of the presence or absence of symptoms. Pregnant women have been used as a sentinel population for other infections, including HIV and hepatitis C.6,10

Chlamydia and gonorrhea screening is recommended for all pregnant women younger than 25 years and for older women who are at increased risk.11,12 More than 50% of pregnant women are younger than 30 years13; thus, they are at higher risk for these infections than the general population. One study assessed infections among pregnant women who were tested by a commercial laboratory from 2005 to 2008.14 That study found that 59% of women who had a maternal serum screen were also tested for chlamydia and gonorrhea, and 3.6% of them had chlamydia and 0.6% had gonorrhea. However, the catchment area for a large diagnostic laboratory changes over time, which may influence trends. In a Southern academic medical center with an urban population demographically similar to ours, 97% of pregnant women were screened for chlamydia and gonorrhea and 11.6% were positive for either.15 Neither of these studies evaluated trends in disease over time.

The 2002 Centers for Disease Control and Prevention sexually transmitted disease treatment guidelines recommended universal chlamydia screening during pregnancy.16 We believe that most if not all women receiving prenatal care at our center have been screened at least once for chlamydia infection during pregnancy in accordance with this Centers for Disease Control and Prevention recommendation. A combination nucleic acid amplification test for chlamydia and gonorrhea was made available at the Medical University of South Carolina (MUSC) in 2003. Approximately 4% to 6% of all women tested at the MUSC have screened positive for chlamydia.17,18 Our specific aim was to assess trends in diagnoses of chlamydia and gonorrhea among pregnant women who received prenatal care and delivered at the MUSC.


Study Design

This retrospective observational study was approved for exempt status by the MUSC's institutional review board (PRO No. 96127). Data were collected from the Perinatal Information System (PINS), a validated internal database of all mother-baby pairs delivering at the MUSC.19 Perinatal Information System variables were abstracted and keyed into the database by trained research staff. We obtained data for all deliveries of at least 1 infant >18 weeks of gestation occurring from January 1, 2008, to December 31, 2018. Women who had more than 1 delivery during the study period were included for each delivery. The PINS database abstraction obtains the outcomes of chlamydial and gonococcal infection from the medical record labor and delivery admission history and physical and discharge summary. A single positive result was counted for each woman during the pregnancy of record. Typically, screening occurred at the first prenatal visit. Repeat tests of cure and evaluation of new infections were not included in our calculations. During the study period, all chlamydia and gonorrhea screening was performed using combined nucleic acid amplification tests (Hologic, Marlborough, MA).

Data Collection and Variables

Variables collected from PINS were as follows: delivery year, maternal age, race/ethnicity, insurer, and chlamydial and gonococcal diagnoses during prenatal care and/or delivery. Maternal race/ethnicity was classified within PINS as Asian, Black, Hispanic, Native American, not specified, and White. Because of relatively low numbers, we created a composite “other race” that included Asian, Native American, and not otherwise specified groups. Insurers were grouped as commercial, Medicaid, and self-pay/indigent.

Statistical Analysis

All data analyses were completed using SAS 9.4 (SAS, Cary, NC). Cochrane-Armitage trend tests were used to assess changes in chlamydial and gonococcal diagnoses by delivery year. The percent of women from each racial/ethnic group with a diagnosis of chlamydia or gonorrhea was calculated using the number of women with a reported diagnosis among the specified racial/ethnic group for the year of delivery divided by the number of women from the racial/ethnic group delivering during the same year. To assess changes in our delivery population, we performed trend analyses of race, insurer groups, and age by delivery year. A subanalysis was performed to evaluate chlamydia diagnosis trends by race and age subgroups.


During the 11-year study period, 24,807 deliveries of infants >18 weeks of gestation occurred. Either chlamydia or gonorrhea was diagnosed for 5.7% (n = 1419) of women, chlamydia alone for 5.0% (n = 1248), gonorrhea alone for 1.2% (n = 303), and both for 0.5% (n = 132; Table 1). The median age of women in the study was 28 years (interquartile range, 23–32 years). Insurance coverage differed according to race/ethnicity: White (69% commercial, 30% Medicaid), Black (65% Medicaid and 34% commercial), Hispanic (47% self-pay, 45% Medicaid, and 8% commercial), and other (64% commercial, 24% Medicaid, and 12% self-pay). Data were rarely missing: insurer (n = 1). All other variables were available for analysis.

TABLE 1 - Maternal Characteristics of Study Participants
Total, n (Column %) Diagnosis of Chlamydia
(Row %)
Diagnosis of Gonorrhea
(Row %)
Pregnant women 24,807 (100) (5.0) (1.2)
Age, y
 <25 7818 (31.5) (11.3) (2.8)
 ≥25 16,989 (68.5) (2.2) (0.5)
 Medicaid 11,425 (46.1) (7.9) (2.1)
 Commercial 11,125 (44.8) (2.1) (0.5)
 Self-pay 2257 (9.1) (5.0) (0.4)
 Black 9954 (40.1) (9.3) (2.5)
 White 10,229 (41.2) (1.7) (0.4)
 Hispanic 4408 (16.3) (3.2) (0.2)
 Other* 576 (2.3) (1.7) (0.3)
Delivery period
 2008 2452 (9.9) (9.5) (2.5)
 2009 2130 (8.6) (10.1) (2.7)
 2010 2157 (8.7) (6.9) (1.3)
 2011 1914 (7.7) (5.8) (1.1)
 2012 1868 (7.5) (4.0) (0.6)
 2013 2089 (8.4) (2.8) (0.6)
 2014 2340 (9.4) (3.1) (0.7)
 2015 2372 (9.6) (3.8) (0.8)
 2016 2417 (9.7) (2.7) (0.8)
 2017 2538 (10.2) (3.6) (1.2)
 2018 2530 (10.2) (3.4) (1.1)
*Other race includes Asian, American Indian, and not otherwise specified.

The percent of women with diagnoses of chlamydia and gonorrhea decreased from the beginning to the end of the study period (9.6%–3.4% and 2.5%–1.1% respectively; P < 0.001 for both trend analyses). Chlamydia diagnoses decreased most dramatically, but diagnoses of both infections decreased from 2008 to 2013 and then remained relatively stable. Black women had decreases in both chlamydia diagnoses (17.4%–6.9%) and gonorrhea diagnoses (5.8%–2.1%) from the beginning to the end of the study period (P < 0.0001 for both; Figs. 1, 2). A significant decrease in chlamydia diagnoses was also seen during this time for White (2.5%–1.1%) and Hispanic (6.3%–3.2%) women (P < 0.0001 and P = 0.007, respectively). White and Hispanic women had relatively few gonococcal diagnoses throughout the study period, and neither group had statistically significant changes over time.

Figure 1:
Trends in chlamydia diagnosis by race and ethnicity. For each year of the study, the percent of women from each racial and ethnic group diagnosed with chlamydia during pregnancy. Cochrane-Armitage trend test statistic for each group: Black, P < 0.0001; White, P < 0.0001; Hispanic, P = 0.007; and other, P = 0.54.
Figure 2:
Trends in gonorrhea diagnosis by race and ethnicity. For each year of the study, the percent of women from each racial and ethnic group diagnosed with gonorrhea during pregnancy. Cochrane-Armitage trend test statistic for each group: Black, P < 0.0001; White, P = 0.62; Hispanic, P = 0.71; and other, P = 0.73.

The population delivering at the MUSC changed between 2008 and 2018. With regard to race and ethnicity, the percent of women who were White increased from 27.5% to 50.2% (P < 0.0001) and Hispanic women decreased from 30.3% to 9.2% (P < 0.0001), but the percent remained about the same for Black women (39.7% and 37.5%) and women of other races/ethnicities (2.5% and 2.5%). The percent of women with commercial insurance increased from 24.8% to 50.9% (P < 0.0001). The percent of women without insurance coverage (self-pay or indigent) decreased from 32.5% to 0.5% (P < 0.0001). The percent of women with Medicaid was relatively unchanged (42.8% and 48.7%). The percent of women 25 years or older increased over time from 53.9% to 78.3% (P < 0.0001). The trends observed for these variables were not linear in shape, but the trajectories described by the change in percentages from the 2008 to 2018 represent a significant downward or upward direction.

We performed subgroup analyses to identify trends in chlamydia diagnoses by race (Black and non-Black) and age (<25 and ≥25 years). Black women in both age groups and non-Black women 25 years or older had statistically significant decreases in diagnoses of chlamydia over time (Fig. 3). The largest decrease in chlamydia diagnoses was among Black women younger than 25 years (n = 4197; 25.4%–14.7%; P < 0.0001). Non-Black women younger than 25 years (n = 3621) also had fewer diagnoses of chlamydia over time (6.5%–4.6%), but the trend was not statistically significant (P = 0.54).

Figure 3:
Trends in chlamydia diagnosis by race and age subgroups. For each year of the study, the percent of women from each race and age subgroup diagnosed with chlamydia during pregnancy. Cochrane-Armitage trend test statistic for each group: Black women <25 (n = 4197), P < 0.0001; Black women ≥25 (n = 5757), P < 0.0001; non-Black women <25 (n = 3621), P < 0.59; and non-Black women ≥25 (n = 11,232), P < 0.0001.


In a population of pregnant women delivering at our urban, academic medical center in the Southeast, we determined that diagnoses of chlamydia and gonorrhea decreased until 2013 and then stabilized. The highest percentages of women diagnosed with either chlamydia or gonorrhea were among young Black women. The percent of women diagnosed with chlamydia decreased significantly over time in most age/race subgroups except for non-Black women younger than 25 years. Diagnoses of gonorrhea during pregnancy were relatively rare except among Black women. Similar to chlamydia, the percent of Black women diagnosed with gonorrhea decreased during the study period. Because the number of deliveries to Black women per year of the study was relatively stable at our urban academic center, we are uncertain why the percent diagnosed with chlamydia and gonorrhea decreased over time. We hypothesize that women younger than 25 years may have experienced increased screening and successful treatment before pregnancy in accordance with national guidelines, thus reducing cases among these vulnerable women.20 Our findings in this sentinel population suggest that the true prevalence of these infections in the population decreased or stabilized, whereas the number of nationally reported positive test results increased.

Our findings offer the advantages of a large sample size and having a denominator—the total number of pregnant women who delivered at our center—that allowed us to calculate the percent with a diagnosis. Similar to Goggins et al.,15 we suspect nearly all pregnant women delivering at our academic center are screened for these infections at least once during pregnancy using accurate diagnostic tests. Our data were collected for 11 years, which provides adequate time for demonstrating trends in disease. Our findings are also strengthened by the stability in delivery numbers of young Black women, who were found to account for most of these diagnoses in pregnancy. The observed percentages of pregnant women diagnosed with chlamydia or gonorrhea in our study, especially among young Black women, were similar to those reported by another academic medical center in the Southeast and in statewide data.15,21 The 2019 South Carolina Department of Health surveillance report of HIV/AIDS and STIs reports that Black women experienced a less significant decline in diagnoses of chlamydia from 2008 to 2018 statewide than we observed among pregnant women at our center.21 Our findings of decreasing diagnoses among pregnant women over time may suggest that the observed increase in nationally reported cases for chlamydia and gonorrhea may reflect increased screening, as suggested by Datta et al.5 However, more sentinel surveillance is needed to support this conclusion.

Our study has several limitations. First, these data reflect trends in a single center in one state in the Southeast and may not be generalizable to the US population. Our retrospective study used data previously abstracted during chart review by trained researchers. Most women were screened for chlamydia and gonorrhea during pregnancy, but we are unable to verify that all were tested because we could not link the PINS data to the electronic laboratory records, and we could not capture the results of screening tests outside the PINS database.

National surveillance has consistently demonstrated increased rates of reported chlamydial and gonococcal cases over the last 5 years, but case report data are limited by the lack of denominators (negative test results). Case reports inform public health officials and health care providers about the potential for STIs among their patient populations. State and federal funding agencies focus on screening, treatment, and prevention strategies based on these data. For our growing and changing US population, collection and reporting of STI rates may need to go beyond case reports to accurately determine trends. Taking into account negative test results and reason for testing might be helpful. Monitoring prevalence in sentinel populations such as pregnant women could be useful.


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