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Disparities in Universal Prenatal Screening for Group B Streptococcus --- North Carolina, 2002--2003
Group B streptococcus (GBS) is a leading cause of neonatal morbidity and mortality in the United States (1). Intrapartum antibiotics administered to women at risk for transmitting GBS to their newborns are effective in preventing perinatal GBS infection (2). In 2002, CDC, the American Academy of Pediatrics, and the American College of Obstetricians and Gynecologists recommended universal prenatal screening for vaginal and rectal GBS colonization at 35--37 weeks' gestation (3--5). To examine prenatal GBS screening among pregnant women in North Carolina, CDC analyzed 2002 and 2003 data from the North Carolina Pregnancy Risk Assessment Monitoring System (PRAMS). The proportions of women reporting prenatal screening for GBS were similar in 2002 and 2003 (70% and 74%, respectively); however, for both years, women of Hispanic ethnicity and women who received prenatal care at a hospital or health department clinic were less likely to report prenatal screening for GBS. These findings underscore the need to increase GBS-related education and prevention activities targeted to these populations.
North Carolina PRAMS is a population-based, random, stratified, monthly mail/telephone survey of women who have recently delivered a liveborn infant. Each month, approximately 200 questionnaires are mailed to women chosen at random from birth-certificate files. After three mailings, attempts are made to contact nonresponders by telephone. Mothers of low-birthweight babies (<2,500 g) are oversampled to ensure adequate coverage. Self-reported survey data are linked to selected birth-certificate data and weighted for sample design, nonresponse, and noncoverage to create the annual PRAMS data sets. These weights make the data representative of all North Carolina women with a liveborn delivery. Because data from 2002 and 2003 were similar for key analysis variables, results are reported for combined data.
This analysis focused on a PRAMS question related to GBS screening that was added to the North Carolina PRAMS survey in 2002. Mothers were asked, "At any time during your most recent pregnancy, did you get tested for the bacteria Group B Strep (or Beta Strep)?" Response categories included "no," "yes," and "I don't know." Because women who responded "I don't know" differed in several demographic characteristics from women who responded "no," these two groups were evaluated separately, with women who responded "yes" as the referent group. Point estimates and confidence intervals were calculated. Predictors of prenatal GBS screening were identified by univariate analysis. All variables associated with GBS screening with p- values <0.2 were evaluated by multivariable analysis by using backwards stepwise logistic regression and controlling for gestational age at delivery. The final multivariable models included main effects (e.g., race, ethnicity, and primary source of prenatal care) that were significant at p<0.05. Two multivariable logistic regression models were constructed: 1) comparing women who were screened for GBS with those who were not screened and excluding those who did not know their screening status and 2) comparing women screened for GBS with those who did not know their screening status and excluding those who were not screened.
During 2002--2003, a total of 235,599 live births occurred in North Carolina; 4,128 women were included in the PRAMS sample, and 3,027 responded (the overall response rate was approximately 73%). Twelve percent of mothers were Hispanic, 52% had a high school education or less, and 48% had Medicaid payment of delivery. Sixty-eight percent of respondents received prenatal care primarily from a private physician or health maintenance organization; 28% received care primarily from a hospital or health department clinic. Less than 1% received no prenatal care.
In 2002 and 2003, 70% and 74% of women, respectively, were screened for GBS; 11% and 8%, respectively, were not screened for GBS; and 19% and 18%, respectively, did not know their screening status. For both years combined, 82% reported that a health-care provider discussed GBS with them, and 82% were tested for human immunodeficiency virus (HIV) during pregnancy.
Among women who knew their GBS screening status, univariate factors significantly associated with lack of GBS screening included age <24 years, high school education or less, Hispanic ethnicity, being unmarried, delivery paid by Medicaid, receipt of prenatal care primarily at a hospital or health department clinic, no insurance before pregnancy, and lack of prenatal testing for HIV (Table 1). In multivariable analysis, Hispanic ethnicity, receipt of prenatal care primarily at a hospital clinic or health department, and lack of prenatal HIV testing were significantly associated with lack of prenatal GBS screening (Table 1).
Univariate factors significantly associated with lack of knowledge of GBS screening status were similar to those associated with lack of GBS screening, with the addition of black race, other race (i.e., other than white or black), unintended pregnancy, and receipt of Women, Infants, and Children (WIC) benefits during pregnancy (Table 2). In multivariable analysis, black race, other race, Hispanic ethnicity, receipt of prenatal care primarily at a hospital or health department clinic, lack of prenatal HIV testing, and Medicaid payment of delivery were all significantly associated with lack of knowledge of GBS screening status (Table 2).
Reported by: M Avery, MA, North Carolina State Center for Health Statistics. HW Brown, S Schrag, D Phil, Div of Bacterial and Mycotic Diseases, National Center for Infectious Diseases, CDC.
The first consensus guidelines for prevention of neonatal GBS disease in the United States were released in 1996 (6). On the basis of available evidence, these guidelines recommended two strategies as equally acceptable: 1) late prenatal culture-based screening for GBS or 2) prophylactic administration of intrapartum antibiotics to women with defined risk factors for GBS, in lieu of screening. New evidence that prenatal culture-based screening is >50% more effective than the risk-based approach (7) led to revised guidelines recommending GBS screening for all pregnant women. These guidelines were released by CDC in July 2002, endorsed by the American Academy of Pediatrics in October 2002, and issued by the American College of Obstetricians and Gynecologists in December 2002 (3--5). The data presented in this report are from 2002, the year the guidelines were issued, and from 2003, the year after the transition. During 2002--2003, the majority (72%) of pregnant women in North Carolina were screened for GBS. GBS screening rates before 2002 in North Carolina are unknown, but the national average GBS screening rate before 2002 was approximately 50% (7), suggesting that the rate of GBS screening in North Carolina might have increased. However, the goal of universal prenatal GBS screening has not yet been attained in North Carolina.
Although the overall reported GBS screening rate among North Carolina PRAMS participants was high during 2002--2003, reported screening rates were substantially below average among Hispanic women, women who received prenatal care primarily from hospital or health department clinics, and women who did not receive other recommended prenatal interventions (e.g., HIV testing). PRAMS data cannot be used to determine whether GBS screening rates are truly lower at hospital and health department clinics, or whether women who seek care in those settings are less likely to report screening. Targeted efforts to promote universal prenatal GBS screening among obstetric health-care providers who serve these populations might be effective in reducing screening disparities in North Carolina.
Nineteen percent of mothers in North Carolina did not know whether they had been screened for GBS during pregnancy, indicating missed opportunities for communication of GBS prevention messages. This finding might be partially explained by language barriers. In addition, providers might not discuss GBS screening with their patients unless they test positive. Overall, approximately half of Hispanic women did not know their GBS screening status, underscoring the need to develop and implement effective educational messages for this population. A national marketing survey of women in 1999 and 2002 indicated that women of black, Asian/Pacific Islander, or other race, women who had attained a high school education or less, and women with low household income had lower awareness of perinatal GBS than other women; overall, 66% of pregnant women had heard of GBS (8). In North Carolina, the same groups at risk for lack of GBS screening were also at risk for not knowing their screening status, as were black women, women of other race, and women whose deliveries were paid for by Medicaid. Women made aware of perinatal GBS disease might be more likely to request prenatal screening and to communicate their screening status to labor and delivery staff, decreasing missed opportunities for prevention. Health-communications messages targeting pregnant women can supplement those targeted to health-care providers, contributing to the overall goal of preventing perinatal GBS disease.
The findings in this report are subject to at least four limitations. First, because PRAMS data are collected by self-reported survey, GBS screening status could not be confirmed. Second, some health-care providers might have discussed GBS with patients without using the language, "Group B Strep or Beta Strep," used in the PRAMS question. Third, because North Carolina is the only state that collected data regarding GBS screening in 2002 and 2003 and attained a PRAMS response rate >70%, these findings cannot be generalized to other areas of the country. Finally, because data about GBS screening were not collected by any state participating in PRAMS before 2002, no baseline PRAMS data are available with which to compare screening rates after the updated guidelines were issued.
In 2003, the year after universal prenatal GBS screening was recommended, the incidence of invasive perinatal GBS disease in the United States declined 34% (9). For continued progress in reducing perinatal GBS disease, prenatal care providers and health educators must reduce disparities in prenatal GBS screening and awareness among minority populations. Three GBS questions are available to all PRAMS-participating states in the standard (optional) component of PRAMS. These questions are 1) "Have you ever heard of the bacteria Group B Strep (Beta Strep) that mothers can pass to their newborns during birth?" 2) "During any of your prenatal care visits, did a doctor, nurse, or other health care worker talk with you about the bacteria Group B Strep (Beta Strep)?" 3) "At any time during your most recent pregnancy, did you get tested for the bacteria Group B Strep (Beta Strep)?" (10). For the Phase Five version of PRAMS, from which data will be available in 2006, 11 states have incorporated questions about GBS; all states are urged to consider adding the questions to their PRAMS surveys.
Information about perinatal GBS disease and resources to promote prevention are available from the CDC GBS website (http://www.cdc.gov/groupbstrep). A consumer education brochure is available in English and Spanish from the website or by mail, Respiratory Diseases Branch, Mailstop C-23, CDC, Atlanta, GA, 30333, or fax, 404-639-3970.
The findings in this report are based, in part, on contributions by P Buescher, Z Gizlice, North Carolina State Center for Health Statistics. C Whitney, MD, Div of Bacterial and Mycotic Diseases, National Center for Infectious Diseases, CDC.
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Date last reviewed: 7/20/2005