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Contents: Original Research

Lack of Availability of Antenatal Vaccination Information on Obstetric Care Practice Web Sites

Chamberlain, Allison T. PhD; Koram, Allison L. MPH; Whitney, Ellen A.S. MPH; Berkelman, Ruth L. MD; Omer, Saad B. MBBS, PhD

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doi: 10.1097/AOG.0000000000001183
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Pregnant women and their infants are at increased risk of developing complications from both influenza and pertussis.1–4 The Centers for Disease Control and Prevention and the American College of Obstetricians and Gynecologists (the College) recommend that pregnant women receive influenza and tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis (Tdap) vaccines during pregnancy.5–8 Although these vaccines help protect the pregnant woman, they also protect the infant through passive transfer of maternally derived antibodies across the placenta to the fetus.9 This protection conferred before birth is believed to be especially important in protecting immunologically naïve infants during their first few months of life, when they are most vulnerable to severe complications from these diseases.10–12

Despite recommendations to receive influenza and Tdap vaccines during pregnancy, antenatal vaccination rates against these two diseases remain low.13,14 Research exploring reasons why pregnant women do not get vaccinated have found that lack of awareness and knowledge about antenatal vaccination are among the key barriers.15–17 With the Internet now being a popular source of health-related information, especially among pregnant women, organizations such as the National Foundation for Infectious Diseases and the College have created web sites dedicated specifically to provision of evidence-based information about antenatal vaccination against influenza and pertussis.18–21 Although these web sites provide abundant resources on antenatal vaccination, women may lack familiarity with these organizations and the information they provide.19

Aside from the role the Internet can play in providing information about vaccination, one of the strongest predictors of antenatal vaccine receipt is a health care provider's recommendation.22,23 Finding ways to couple the influence of a health care provider's recommendation with evidence-based information on the Internet may serve to educate expectant mothers and prevent acquisition of misinformation. One potential avenue through which to accomplish this could be through obstetric providers' web sites. The objective of this study is to examine the availability of antenatal vaccination information on obstetric practice web sites in the United States.24–26


For this cross-sectional study, we assembled our sample of obstetric practice web sites in the United States from a random sample of obstetric care providers obtained from is a publicly available database of health care providers in the United States and can be sorted by medical specialty, health care provider location, and patient ratings. For this analysis, we used because of its comprehensiveness and accessibility.27,28 Because this study did not involve interaction with human subjects or collect any private information about individuals, this study was not reviewed by an institutional review board.

Because the physician search features within require a user to limit one's search by state, we compiled a thorough list of all obstetric care providers in the United States by generating comprehensive lists within each state. To obtain these state-specific lists, our search criteria included state, specialty (obstetrics and gynecology), and condition treated (pregnancy). Each state-specific list was then sorted alphabetically by last name and numbered sequentially. No efforts were made to assess patient satisfaction with health care providers or of preference for certain health care providers over others.

For our sample size, we decided to review 1,000 practice web sites, a number conventional for national surveys and polls.29 To generate a random and nationally representative sample, the number of practice web sites selected per state was determined according to each state's proportion of the total number of obstetric care providers listed on as of August 18, 2014. After the numbers needed per state were determined, we used SAS 9.3 to generate lists of random numbers for each state. Each list contained a total count of random numbers that was three times greater than the target sample size to accommodate practices not meeting our inclusion criteria. We used each state's random number list to select health care providers from the numbered state-specific lists of health care providers from We then used the Google search engine to search for each health care provider and identify their practice web site(s). Each practice web site was then screened for inclusion according to the criteria outlined subsequently; practice web sites were screened until the total number of unique obstetric practice web sites needed per state was reached.

Obstetric practice web sites were excluded from the final sample if 1) the primary practice location of the health care provider selected from was not in the target state; 2) there was no practice web site associated with the selected health care provider; 3) the practice did not provide prenatal care as determined from information provided on the practice web site; 4) the practice appeared to be permanently closed; or 5) the practice had an apparent military affiliation. Obstetric practice web sites were also excluded if they had previously been included in the sample.

Obstetric practice web site data were collected between September 25, 2014, and November 12, 2014. This timeframe was selected to align with the period during which seasonal influenza vaccination was likely promoted for the 2014–2015 influenza season. From each practice web site, data were collected on practice location(s), affiliation with a hospital-based or multispecialty practice, number of physicians (ie, medical doctors and doctors of osteopathic medicine), staff composition (ie, presence of certified midwives and nurse practitioners), availability of information on antenatal vaccinations (influenza, Tdap, other), human papillomavirus infection vaccinations, childhood vaccination, and other preventive prenatal health information, including safe foods to eat during pregnancy, safe medications to take during pregnancy, and safe exercises during pregnancy. Apparent posting date of antenatal vaccination information was obtained by examining web site copyright dates, dates of last update, language used to describe the antenatal vaccination recommendations, or all of these. Antenatal vaccination information was considered up to date if either the post date or language used to describe the vaccine recommendations aligned with the 2012 change in antenatal Tdap recommendations to vaccinate women during every pregnancy.7 The presence of an obstetrics-related blog or advertisement of a practice-sponsored Facebook page was also recorded. If present, the content of these social media platforms was examined back to September 2013 for the presence of information related to antenatal vaccination.

Web sites or practice-sponsored blogs or Facebook pages explicitly providing information about antenatal influenza or pertussis vaccines were considered as providing information on antenatal vaccination. Information embedded within the text of the web site, provided within downloadable pregnancy-related documents (eg, prenatal checklists, pregnancy resource packets), or included as a link(s) to external sources (eg, Centers for Disease Control and Prevention, the College, the National Foundation for Infectious Diseases) was reviewed. If antenatal vaccination information was provided in any of these formats, the practice web site was considered as posting information on antenatal vaccination.

Frequencies and bivariate associations were calculated using SAS 9.3. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to determine associations between provision of information about antenatal vaccination and other practice characteristics. χ2 tests were used to determine the significance of bivariate associations. P values ≤.05 were considered statistically significant.


On August 18, 2014, there were 53,261 obstetric care providers listed in the United States on Of this total, 1,493 (2.8%) obstetric care providers were then entered into Internet search engines to identify their practice web sites (Fig. 1). Four hundred ninety (32.8%) providers were excluded from the study for not meeting eligibility criteria. Of those excluded, 203 were excluded for not having a practice web site, suggesting that approximately 86% of obstetric providers (1,290/1,493) are associated with practices that host web sites. The final sample used for analysis included 1,003 (67.2%) practice web sites.

Fig. 1
Fig. 1:
Screening and inclusion of obstetric care providers' web sites. *Obstetric providers listed on as of August 18, 2014.Chamberlain. Antenatal Vaccines and Obstetric Care Web Sites. Obstet Gynecol 2016.

Practice web sites contained varying amounts of information on prenatal preventive health activities. Of the 1,003 web sites included in the analysis, 229 (22.8%) web sites posted information pertaining to antenatal vaccinations compared with 409 (40.8%; P<.001), 370 (36.9%; P<.001), and 386 (38.5%; P<.001) that posted information on safe foods, safe medications, and safe exercises, respectively, during pregnancy (Table 1). Four hundred sixty-five web sites (46.4%) posted no information on any of these prenatal health topics.

Table 1
Table 1:
Practice Characteristics and Content of Publicly Available Information on Obstetric Care Practice Web Sites

Overall, 129 web sites (12.9%) mentioned both antenatal influenza and antenatal Tdap vaccination with 105 (10.5%) providing up-to-date information (Table 2). Seventy-eight (7.8%) web sites mentioned only antenatal influenza vaccination and another 14 (1.4%) mentioned only Tdap. Additionally, 26 (2.6%) web sites mentioned other antenatal vaccinations including hepatitis A, hepatitis B, and travel vaccines. All practices mentioning influenza, Tdap, or both vaccines promoted immunization during pregnancy; only one practice web site (<0.01%) suggested to avoid immunizations during pregnancy, but no additional information was provided on what immunizations to avoid.

Table 2
Table 2:
Proportions of Web Sites Providing Information on Antenatal Influenza, Tetanus, Diphtheria, and Acellular Pertussis Vaccination, or Both

Based on updated vaccine language and copyright dates, 152 (66.4%) web sites providing any antenatal vaccination information presented up-to-date information. Of the 538 web sites posting at least some information on antenatal vaccinations, safe foods, safe medications, or safe exercise during pregnancy, 19.5% posted up-to-date information on both antenatal influenza and Tdap vaccination (Table 2).

Practices with more than five physicians were significantly more likely to provide antenatal vaccination information on their web sites than practices with less than five physicians (27.4% compared with 18.0%; OR 1.72, 95% CI 1.27–2.32) (Table 3). Web sites advertising the presence of nurse practitioners were significantly more likely to provide information on antenatal vaccination (28.8% compared with 19.0%; OR 1.72, 95% CI 1.28–2.31), whereas web sites associated with hospital-based or multispecialty practices were significantly less likely to include information on antenatal vaccinations compared with nonhospital-based practices (10.6% compared with 27.0%; OR 0.34, 95% CI 0.21–0.54). Provision of information on childhood vaccines was significantly associated with providing information on antenatal vaccinations. Additionally, information on safe foods, safe medications, and safe exercise during pregnancy were all significantly associated with provision of information about antenatal vaccinations. Practices that posted information on antenatal influenza vaccination were significantly more likely to also post information on antenatal Tdap vaccination (OR 92.36, 95% CI 50.76–168.05, P<.001).

Table 3
Table 3:
Associations Between Practice Characteristics and Other Web Site Content on Presence of Antenatal Vaccination Information on Obstetric Care Practice Web Sites Offering Any Antenatal Vaccine Information


From a national random sample of 1,003 obstetric practice web sites in the United States, we found that less than one fourth of web sites provide information on antenatal vaccinations. Even fewer (10.5%) provide up-to-date information on both influenza and Tdap vaccination during pregnancy. These percentages are significantly lower than the approximately 40% of obstetric practice web sites that provide information on topics such as safe foods, medications, and exercise during pregnancy. With antenatal vaccination becoming an increasingly important part of prenatal care, these findings suggest substantial room for expansion on the part of obstetric practices to consider using their web sites as sources of reliable, evidence-based information on antenatal vaccination.

In nearly every study exploring facilitators to antenatal vaccine receipt, a health care provider's recommendation is associated with actual receipt or willingness to vaccinate.22,23,30,31 These findings suggest that women are strongly influenced by their obstetric care providers regarding decisions about antenatal vaccination. Additionally, pregnant women routinely seek health and vaccine-related information on the Internet,25,32 sometimes to fill knowledge gaps still remaining after prenatal care visits.25,32,33 In one study conducted in 2014 among 200 primagravida women, the most commonly cited source of information about childhood vaccines was an Internet search engine.34 Given that antenatal vaccination is recommended for some infections and Internet searches on vaccination can generate considerable amounts of nonevidence-based information, obstetric providers should view their practice web site as a tool to guide their patients to reputable information they endorse.

With close to 40% of the web sites reviewed for this study providing information on prenatal health topics such as safe foods, medications, and exercise, some obstetric health providers already use their web sites to provide information on activities that prevent adverse health outcomes for mothers and infants. Understanding the variability in posting on these preventive health topics compared with vaccination is worth exploring. Reasons could be simple (eg, had not yet considered adding vaccination content) to more complex reasons potentially related to concerns about vaccine safety, financial investments needed to initiate a vaccine program, and perceptions that vaccination is not within the traditional purview of an obstetrician's role.31,35–38 Determining the extent to which these more substantive reasons contribute to the low prevalence of mentioning antenatal vaccination on their web sites is important. Equally important, however, is improving health care providers' awareness of their influence on pregnant women's decisions to vaccinate and the key role their web sites could play in educating and empowering their pregnant patients.

Although posting on other preventive prenatal care topics was more prevalent than posting on antenatal vaccination, it is worth noting that 46% of web sites did not post any information on these topics. Combining this percentage with the approximately 15% of health care providers excluded from the study for not appearing to have a practice web site, more than 60% of obstetric care providers in the United States may be missing a key way to educate their patients about important prenatal health topics of which vaccination is just one.

As may be expected, we found that posting on other preventive prenatal health topics was positively associated with posting on antenatal vaccination. However, practices with less than five physicians and practices affiliated with larger health networks such as hospitals or multispecialty clinics were less likely than other practices to post on antenatal vaccination. This lack of vaccine information may reflect their inability to either afford staff time to update their web sites (smaller practices) or control the content on their web sites (practices whose web sites are controlled primarily through a larger health care organization). Whatever the reasons, it remains important for practices to consider the implications of not posting on a topic such as vaccination. When ample information is available on other preventive health topics but not on antenatal vaccination, the absence of the information may generate concern, prompting women to turn elsewhere (likely on the Internet) for potentially less reliable information. For health care providers looking to add content about antenatal vaccination to their web sites, Table 4 provides a list of reputable web sites dedicated to the topic.

Table 4
Table 4:
Selected Online Resources for Evidence-Based Antenatal Vaccination Information

This study has some important limitations. First, this study was based entirely on information publicly available on the obstetric practice web sites at one point. Some obstetric practices may have updated their web sites after we examined them, and these changes would not have been captured in our data collection. We made no attempts to contact the practices to verify information posted on their web sites. We did, however, specifically examine all of the practice web sites during the Fall 2014 influenza vaccination period in an effort to capture vaccination data during the time in which promotion of seasonal influenza vaccination should have been highest. Additionally, by Fall 2014, the updated recommendation to vaccinate pregnant women with Tdap during every pregnancy had been in place for 2 years, providing ample time for practitioners to be aware of their role in facilitating routine antenatal Tdap vaccination.

A key strength of this study is the nationally representative nature of the sample. As a result of the comprehensiveness and widespread accessibility of, every physician listed on the web site had the potential to be selected and their web site examined for potential inclusion in the study sample. This suggests that our study estimates the general prevalence of antenatal vaccination information provided on obstetric practice web sites.

With a health care provider's recommendation being such an influential factor in acceptance of antenatal vaccination, obstetric providers should begin to view their practice web sites as direct extensions of their ability to influence patients. With such a complex and important topic as vaccination, women should be able to readily access the information their trusted health care providers endorse. By providing access to evidence-based information about antenatal vaccination on their practice web sites, obstetric providers can direct patients to the most salient and reliable information available. This education can facilitate discussions, yielding more informed conversations during clinic visits and help prevent the acquisition of misinformation available through less trusted Internet outlets.


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© 2016 by The American College of Obstetricians and Gynecologists. Published by Wolters Kluwer Health, Inc. All rights reserved.