- Research article
- Open Access
- Open Peer Review
Development and initial testing of a GDM information website for multi-ethnic women with GDM
© Carolan-Olah et al. 2015
- Received: 22 October 2014
- Accepted: 28 May 2015
- Published: 5 July 2015
Gestational diabetes mellitus (GDM) affects approximately 5–15 % of pregnant women in Australia. Highest rates are seen among women who are obese, from specific ethnic backgrounds and low socio-economic circumstance. These features also impact on uptake of self-management recommendations. GDM that is not well managed can give rise to serious pregnancy complications. The aim of this project was to develop and test an intervention to improve knowledge of GDM and GDM self-management principles.
A web-based intervention, consisting of resources aimed at a low level of literacy, was developed and tested among multi-ethnic women at a metropolitan hospital in Melbourne Australia. A basic one-group pre-test/post-test design was used to explore the impact of the intervention on knowledge, in 3 domains: (1) Knowledge of GDM; (2) food values, and;(3) GDM self-management principles. Questionnaire data was analysed using Statistical Package for the Social Sciences (SPSS), version 21.0. Fisher’s exact test was used to test for an improvement in each knowledge scale.
Twenty-one women with GDM, from multi-ethnic backgrounds, participated in the testing of the intervention. Results indicated that the intervention was effective at improving knowledge scores and this effect was greatest in the first domain, knowledge of GDM. Although some improvement of knowledge scores occurred in the other two domains, food values and self-management principles, these improvements were less than expected. This finding may relate to a number of misunderstandings in the interpretation of the web resource and survey questions. These issues will need to be resolved prior to proceeding to a clinical trial.
Initial results from this study look promising and suggest that with some improvements, the intervention could prove a useful adjunct support for women with GDM from multi-ethnic and low socio-economic backgrounds. Conducting a randomised controlled trial is feasible in the future and will provide a useful means of examining efficacy of the intervention.
- Gestational diabetes
In Australia, Gestational Diabetes Mellitus (GDM) affects approximately 5 % of pregnant women overall  and figures are considerably higher among women from specific ethnic backgrounds, such as Asian and South Asian. In such groups, GDM rates may be 2–3 times higher than national rates [2, 3]. These high rates are a concern as GDM is linked to a number of adverse outcomes for mothers and infants. Mothers are more likely to experience: induction of labour; pre-term birth, caesarean section, hypertension and extended hospital stay . Infants of mothers with GDM are predisposed to hypoglycaemia , higher rates of stillbirth, macrosomia and birth injury , low apgar scores, admission to special care nursery, and longer hospital stays [1, 4]. Careful management of GDM reduces these risks [4, 6].
Self-care is the most usual approach to GDM management and women are taught to: monitor their blood glucose levels; adjust their dietary intake to GDM recommendations, and; increase physical activity, in a bid to maintain blood glucose levels within normal limits. These changes can be very difficult and, for some women quite extensive, due to previous dietary and exercise habits. For these reasons, many women struggle to adhere to GDM recommendations [7–10], particularly as changes must be adopted immediately [8, 11]. Additionally, in order to successfully self-manage the condition, women need to understand GDM, the importance of self-management , what constitutes a healthy diet, the impact of different foods on blood glucose levels, and the amount and type of exercise to undertake . Emotional support is critical to motivation and a number of studies indicate that such support contributes positively to GDM skills development [7, 10]. Conversely, a number of factors are identified as likely to impact negatively on the adoption of health recommendations. These factors include: low educational attainment , limited health literacy , and low levels of English language proficiency . Each of these features increase the likelihood that women will experience significant difficulty self-managing their GDM.
Overall, there is a need for GDM interventions that target low income, ethnically diverse and low literacy groups, as these groups are at high risk of developing GDM. However, despite this clear need, such programs are rare, and only two published studies were identified that reported on interventions to improve levels of knowledge and GDM outcomes among low socio-economic and minority groups [15, 16]. In the first instance, Hoppichler and Lechleitner  tested an intervention, which involved repeated intensive dietary counselling, among locally born women with GDM, compared to low literate migrant Turkish women, also with GDM, in Austria. Secondly, Mendelson et al.,  used a similar approach for low income Mexican-American women with GDM, in California, USA. Both studies considered their interventions successful and also emphasised the importance of ensuring acceptability of educational resources [15, 16]. Furthermore, the literature suggests that in order for GDM interventions to be effective in low income groups, resources need to be pitched at a low level of health literacy  and experts in the field recommend using strategies such as pictorial representation of important information and repetition of simple instructions . The provision of culturally sensitive resources is also recognised as important and as likely to improve acceptability and uptake of the intervention [15, 19].
With this information in mind, the website intervention, reported in this paper, aimed to address such issues as cultural sensitivity, low health literacy and low levels of English proficiency, in the belief that women with GDM need resources that they understand and that are culturally relevant to them. The intervention was developed for use in a low socio-economic area of Melbourne , where women incur a higher GDM incidence than that recorded nationally . In this area, there are high levels of obesity , and as many as one third of the population speak a language other than English at home . In this paper, development and initial testing of the intervention, is discussed. The intervention was planned to serve as an adjunct to routine educational sessions by the dietician and diabetes educator. The team also aimed to test ease of use, relevance and acceptability of the website for the target group of women, and to consider the feasibility of proceeding to a clinical trial.
One of the difficulties with GDM is a tendency for women to underestimate the seriousness of the condition, based on it’s transient quality and we aimed to address this difficulty by re-iteration of the impact, for the baby, of unmanaged GDM. We choose this approach, as in our earlier study, we found that ‘thinking about the baby’ was a powerful motivator for women to manage their GDM .
The overall challenge was to convey the urgency of behavioural change without unnecessarily alarming the women.
A basic pre-test/post-test survey questionnaire design was used to measure differences, if any, in knowledge of GDM, food values and GDM self-management principles before and after the intervention. This particular approach was chosen as it is considered suitable for measuring changes in behaviours or attitudes  and it has been successfully used in a number of nursing and health related studies [31, 32]. Additionally, we intended this testing of the intervention as a means of identifying any weaknesses in the design, and any deficits in general user-friendliness and acceptability for the target group of women. For these reasons, we included three additional questions in the post-test questionnaire, where participants were asked to give feedback on the intervention, in terms of (1) ease of use; (2) value of the information on the website; and (3) any changes or inclusions they would recommend.
Description of intervention
Recruitment and data collection
Diagnosis of GDM
More than 18 years of age
Conversational English, as this initial website is in English
Ethics approval was granted by the Western Health (Sunshine Hospital) low risk ethics panel (HREC/11/WH/81). Women were given a verbal description of the intervention and advised that participation was voluntary. Interested women were invited to go through the website using the touchscreen or computer in the clinic waiting room. Those who agreed to participate, provided written consent. Participants filled in a pre-test questionnaire (approximately 5 min), perused the website while waiting for their clinic appointments, and filled in the post-test questionnaire (approximately 5 min) at their next appointment one week later. A research assistant was available to assist the women to navigate the website and to read out the questionnaire and record the participant’s responses, if the participant wished. Five participants requested this level of assistance.
A cross table was created comparing the improvement in each of the three scores (GDM, Food, Self-management) against the participant’s level of education (Table 2). Fisher’s Exact test was used to test for an association between each scale’s improvement and the education variable as this test is suitable for small data sets . The P-values for these tests are provided below each sub-table.
Country of birth
Years of education
<6 (did not complete primary school)
11 years or fewer – did not completed high school
12 years or more –completed high school
Knowledge scores by education level
11 years or fewer - Not completed high school
More than 12 years - Completed high school
GDM score change from pre to post*
Improved or stayed at 100 %
Stayed the same if below 100 %, or worsened
Food score change from pre to post**
Improved or stayed at 100 %
Stayed the same if below 100 %, or worsened
Self-management score change from pre to post***
Improved or stayed at 100 %
Stayed the same if below 100 %, or worsened
Knowledge scores composite
Percentage of sample who improved
95 % Confidence interval
or stayed at 100 % correct post-intervention
(44.0 %, 89.7 %)
(26.0 %, 74.0 %)
(16.3 %, 61.6 %)
Ease of use
Easy to use
Not very useful
This paper reports on the development and initial testing of a new intervention, which aims to support women, from multi-ethnic and low health literacy backgrounds, to self-manage their GDM. This intervention has been developed in English initially and there are plans to later amend the program for the Vietnamese community, who have low levels of English language fluency. The aim of this stage of the project was to test the acceptability, ease of use, and usefulness of the intervention for the target population. We also aimed to identify any issues with the website and content and to ascertain both the improvements necessary and the feasibility of proceeding to a clinical trial. Overall, the findings suggest that women found the intervention useful and easy to use. The testing also revealed a number of areas that were effective at promoting greater knowledge scores and a further number of areas that required some improvement. Both of these findings are discussed below.
In the first instance, the intervention proved effective at increasing women’s knowledge scores. The largest improvement occurred in domain 1: Knowledge of GDM and over 70 % of women improved their knowledge scores or stayed at 100 % post-intervention. This is an important effect as knowledge acquisition is established as a necessary first step in understanding and motivation for behavioural change . Moreover, a number of prior studies indicate that women with GDM often complain that the information they receive is insufficient, incomplete or does not meet their needs [11, 33, 40]. Participants in these studies indicate that their efforts to self-manage their GDM are often frustrated by a lack of such knowledge [10, 11]. Feedback in this study suggests that our intervention assists by providing material that participants consider useful and accessible.
In the second domain, knowledge of food, there was a modest improvement in knowledge scores, although the improvement was less than anticipated. This finding may in part be explained by two factors. Firstly, a number of women answered question 2 (Fig. 2, food value of butter) incorrectly, and the percentage getting the question wrong increased considerably in the post-test, which had a negative impact on overall improvement scores. This finding may relate to the fact that many women in the area do not use butter for cooking or food preparation, and therefore may be unfamiliar with this food. However, this explanation does not explain why scores disimproved so markedly from pre-test to post-test. For the future, we plan to simplify and change this question to butter/oil/ghee, which is more in line with local cooking practices. Secondly, a further explanation of repeated incorrect answers about food values may reflect entrenched cultural beliefs about food, and this is something that requires further exploration. In particular, a qualitative exploration of food beliefs and taboos is planned among pregnant women, from specific ethnicities, in our area.
The smallest improvement was recorded in the third domain, knowledge of self-management, where little more than one third of women improved their knowledge scores or remained at 100 %. This finding is in part explained by the misinterpretation of question 3 (Fig. 2), where many women got the answer correct in the first instance and then incorrect in the post-test. Based on this feedback, we plan to amend the text about exercise both in the intervention and in the questionnaire. Participants also got some questions, with more than one correct answer, partially correct, by identifying one variable rather than all correct variables. As these questions required identification of all correct variables to score, this partial knowledge was not recorded. Question 4 (Fig. 2) provides a good example and many women identified one or two healthy snacks but not all four. Nonetheless, these questions provide valuable feedback and allow identification of areas where the required knowledge uptake is insufficient. For example, for question 4, most participants recognise an apple and yoghurt as appropriate snacks, while many do not recognise nuts or crackers and cheese as appropriate. To address this deficit, we may need to further clarify the section, in the intervention, outlining snacks and perhaps add some additional ethnic specific snacks to the questionnaire.
Greater improvement of scores were seen among women with lower rather than higher educational levels. It is not immediately clear what this finding means, however, one possible explanation is that women of lower educational levels may be the most likely to benefit from this intervention, as they are the most likely to have low levels of health literacy . They may also have limited access or ability to decipher health information . Thus, the intervention may offer more support for learning for women with lower educational levels compared to higher levels.
In the literature, fostering knowledge and beliefs, is seen as a necessary first step to health related behavioural change  and self-management skill development . This approach is also considered to be in line with adult learning theory , where the individual is empowered and motivated by understanding the importance of change . Similarly, a number of studies have found that women are highly motivated to adopt healthy behaviours, in pregnancy to protect the unborn baby . This effect may be even stronger during GDM self-management, if women fully understand the implications of GDM for the child’s future health [8, 45]. Additionally, knowledge of food values, and the basic constituents of a healthy diet, have been positively associated with good nutritional practices, such as eating sufficient fruit and vegetables [46, 47]. Worsley suggests that education may play a part in effecting such behavioural change by encouraging a different set of beliefs about food (, p. 583).
However, caution is also advised and a number of studies suggest that knowledge of prudent health behaviours alone, is not sufficient to bring about behavioural change [9, 46, 48]. These studies recognise that dietary changes are difficult and impacted by many factors such as food preferences, cravings and social eating  and socio-economic circumstance, food habits and food availability .
Strengths and limitations
The aim of this basic one-group pre-test/post-test study was to explore the impact of the newly developed intervention on knowledge scores in three domains: Knowledge of GDM; food values, and GDM self-management principles. The study has been successful in that it has provided useful feedback that will enable the researchers to improve the intervention. In particular, we plan to clarify the content, amend inconsistencies and ambiguities and add additional information where indicated. These efforts will lead to an improvement of the intervention and a tailoring of the intervention to the needs of the target population. Nonetheless, although the study has achieved the stated aims, some limitations are also present and the small sample size has limited the value of statistical evaluation. For example, p values are very large and although differences in knowledge scores are evident, a larger sample size is required in order to be confident that the associations observed are not just chance. Similarly, there were more women who improved in the 11 years or fewer education group compared to more than 12 years and the meaning of this finding might also be clearer in a larger sample. Finally, only women who spoke conversational English were eligible to participate in this initial testing of the intervention, and this is a limitation that we aim to address in the next phase of the project.
Implications for practice
The development and testing of the intervention described here has a number of important implications for practice. In the first instance, the demographic profile of GDM, with increased risk factors for multi-ethnic, low socio-economic and poorly educated women, highlights the need for culturally acceptable educational resources pitched at a low level of literacy. Addressing this need is very important as rates of GDM are continuing to increase dramatically in these groups with potentially devastating consequences for mothers and infants and multi-generational effects for families.
In conclusion, the intervention was effective at improving knowledge scores for women with GDM in the three tested domains: Knowledge of GDM; knowledge of food; and, knowledge of GDM self-management principles, and also that the intervention is a useful adjunct to the routine education sessions women with GDM attend, in our area. Testing has revealed a number of issues, such as ambiguity of information around physical exercise in GDM and some foods. These issues require attention prior to proceeding to a trial.
Many thanks to dietetics team at Western Health, Sunshine Hospital for their assistance, recommendations and advice during the development of dietary resources. Thanks also to the participants who were involved in testing the intervention. This study was made possible through funding from the Ian Potter Foundation, Melbourne, grant reference 201200017.
- Australian Institute of Health and Welfare (AIHW). Diabetes in pregnancy: its impact on Australian women and their babies. Canberra: AIHW; 2010.Google Scholar
- Carolan M. Gestational diabetes mellitus among women born in South East Asia: A review of the evidence. Midwifery. 2013;29(9):1019–26.View ArticlePubMedGoogle Scholar
- Carolan M, Davey MA, Biro MA, Kealy M. Maternal age, ethnicity and gestational diabetes mellitus. Midwifery. 2012;28(6):778–83.View ArticlePubMedGoogle Scholar
- Cheung NW. The management of gestational diabetes. Vasc Health Risk Manag. 2009;5:153–64.View ArticlePubMedPubMed CentralGoogle Scholar
- Yogev Y, Visser GHA. Obesity, gestational diabetes and pregnancy outcome. Semin Fetal Neonatal Med. 2009;14(2):77–84.View ArticlePubMedGoogle Scholar
- Glastras S, Fulcher G. Guidelines for the management of gestational diabetes in pregnancy. Clin Pract. 2012;9(2):161–70.View ArticleGoogle Scholar
- Persson M, Winkvist A, Mogren I. 'From stun to gradual balance'- women's experiences of living with gestational diabetes mellitus. Scand J Caring Sci. 2010;24(3):454–62.View ArticlePubMedGoogle Scholar
- Carolan M. Women's experiences of gestational diabetes self-management: A qualitative study. Midwifery. 2013;29(6):637–45.View ArticlePubMedGoogle Scholar
- Hui AL, Sevenhuysen G, Harvey D, Salamon E. Food choice decision-making by women with gestational diabetes. Can J Diabetes. 2014;38(1):26–31.View ArticlePubMedGoogle Scholar
- Carolan M, Gill GK, Steele C. Women's experiences of factors that facilitate or inhibit gestational diabetes self-management. BMC Pregnancy Childbirth. 2012;12:99.View ArticlePubMedPubMed CentralGoogle Scholar
- Evans MK, O'Brien B. Gestational diabetes: the meaning of an at-risk pregnancy. Qual Health Res. 2005;15(1):66–81.View ArticlePubMedGoogle Scholar
- Chung JH, Voss KJ, Caughey AB, Wing DA, Henderson EJ, Major CA. Role of patient education level in predicting macrosomia among women with gestational diabetes mellitus. J Perinatol. 2006;26(6):328–32.View ArticlePubMedGoogle Scholar
- Zanchetta MS, Poureslami IM. Health literacy within the reality of immigrants’ culture and language. Can J Public Health. 2006;97 Suppl 2:S26–30.PubMedGoogle Scholar
- Pope C. Addressing limited English proficiency and disparities for hispanic postpartum women. J Obstet Gynecol Neonatal Nurs. 2005;34(4):512–20.View ArticlePubMedGoogle Scholar
- Mendelson S, McNeese-Smith D, Koniak-Griffin D, Nyamathi A, Lu MC. A community-based parish nurse intervention program for Mexican American women with gestational diabetes. JOGNN/NAACOG. 2008;37(4):415–25.Google Scholar
- Hoppichler F, Lechleitner M. Counseling programs and the outcome of gestational diabetes in Austrian and Mediterranean Turkish women. Patient Educ Couns. 2001;45(4):271–4.View ArticlePubMedGoogle Scholar
- Rosal MC, Goins KV, Carbone ET, Cortes DE. Views and preferences of low-literate hispanics regarding diabetes education: Results of formative research. Health Educ Behav. 2004;31(3):388–405.View ArticlePubMedGoogle Scholar
- Negarandeh R, Mahmoodi H, Noktehdan H, Heshmat R, Shakibazadeh E. Teach back and pictorial image educational strategies on knowledge about diabetes and medication/dietary adherence among low health literate patients with type 2 diabetes. Prim Care Diabetes. 2013;7(2):111–8.View ArticlePubMedGoogle Scholar
- Rosal MC, Ockene IS, Restrepo A, White MJ, Borg A, Olendzki B, et al. Randomized trial of a literacy-sensitive, culturally tailored diabetes self-management intervention for low-income Latinos: Latinos en control. Diabetes Care. 2011;34(4):838–44.View ArticlePubMedPubMed CentralGoogle Scholar
- ABS: Australian Bureau of Statistics. 2033.0.55.001 - Census of Population and Housing: Socio-Economic Indexes for Areas (SEIFA). Canberra: Australian Bureau of Statistics; 2006.Google Scholar
- Department of Human Services. Well being and lifestyle - the evidence 2006, North West Region. Melbourne, Victoria: Department of Human Services; 2008.Google Scholar
- INWMML. Inner North West Melbourne Medicare Local. Inner North West Melbourne Medicare Local Whole of Region Needs Assessment. 2012.Google Scholar
- Department of Human Services. Western Metropolitan Region Health and Social Wellbeing Profile. Public Health and Strategic Melbourne 2002 [cited 2013 25 February 2013]; Available from: http://www.health.vic.gov.au/archive/archive2014/nphp/publications/phpractice/phpractice_project/findingsandrecs.pdf.
- Homko CJ, Sivan E, Reece EA. The impact of self-monitoring of blood glucose on self-efficacy and pregnancy outcomes in women with diet-controlled gestational diabetes. Diabetes Educat. 2002;28(3):435–43.View ArticleGoogle Scholar
- Murphy A, Guilar A, Donat D. Nutrition education for women with newly diagnosed gestational diabetes mellitus: small-group vs. individual counselling. Can J Diabetes. 2004;28(2):147–51.Google Scholar
- Speck M. Best practice in professional development for sustained educational change. Spring: ERS Spectrum; 1996. p. 33–41.Google Scholar
- Knowles MS. Andragogy, not pedagogy. Adult Leader. 1968;16(10):350–2. 10.Google Scholar
- Leventhal H, Meyer D, Nerenz D. The common-sense representation of illness danger. Contributions to medical psychology. 2nd ed. New York: Pergamon; 1980.Google Scholar
- Hagger MS, Orbell S. A meta-analytic review of the common-sense model of illness representations. Psychol Health. 2003;18(2):141–84.View ArticleGoogle Scholar
- Polit DF, Beck CT. Nursing Research: Generating and Assessing Evidence for Nursing Practice. 9th ed. Philadelphia: Wolters Kluwer/ Lippincott; 2012.Google Scholar
- Wallström A, Frisman GH. Facilitating early recovery of bowel motility after colorectal surgery: A systematic review. J Clin Nurs. 2014;23(1–2):24–44.View ArticlePubMedGoogle Scholar
- Wilkinson A, Whitehead L, Ritchie L. Factors influencing the ability to self-manage diabetes for adults living with type 1 or 2 diabetes. Int J Nurs Stud. 2014;51(1):111–22.View ArticlePubMedGoogle Scholar
- Carolan M, Steele C, Margetts H. Knowledge of gestational diabetes among a multi-ethnic cohort in Australia. Midwifery. 2010;26(6):579–88.View ArticlePubMedGoogle Scholar
- Dunn SM, Bryson JM, Hoskins PL, Alford JB, Handelsman DJ, Turtle JR. Development of the diabetes knowledge (DKN) scales: forms DKNA, DKNB, and DKNC. Diabetes Care. 1984;7(1):36–41.View ArticlePubMedGoogle Scholar
- Gastrich MD, Peck S, Janevic T, Bachmann G, Lotwala N, Siyam A. Gestational diabetes mellitus: An educational opportunity. J Diabetes Nurs. 2013;17(6):220–4.Google Scholar
- Nicolas-Rocca TS, Schooley B, Joo SJ. Design and development of a patient-centered e-health system to improve patient understanding at discharge. Comm Assoc Inform Syst. 2014;34(1):453–76.Google Scholar
- Yin HS, Gupta RS, Tomopoulos S, Wolf MS, Mendelsohn AL, Antler L. Readability, suitability, and characteristics of asthma action plans: Examination of factors that may impair understanding. Pediatrics. 2013;131(1):e116–26.View ArticlePubMedGoogle Scholar
- Preacher KJ, Briggs, NE. Calculation for Fisher's Exact Test: An interactive calculation tool for Fisher's exact probability test for 2 × 2 tables. Available from: http://www.quantpsy.org/fisher/fisher.htm. 2001.
- Porcheret M, Main C, Croft P, McKinley R, Hassell A, Dziedzic K. Development of a behaviour change intervention: A case study on the practical application of theory. Implement Sci. 2014;9(1):42.Google Scholar
- Heuberger R. Increasing empathy, knowledge, and skills regarding gestational diabetes. Top Clin Nutr. 2010;25(3):250–5.View ArticleGoogle Scholar
- Nutbeam D. Health literacy as a public health goal: a challenge for contemporary health education and communication strategies into the 21st century. Health Promot Int. 2000;15(3):259–67.View ArticleGoogle Scholar
- Morahan-Martin JM. How internet users find, evaluate, and Use online health information: a cross-cultural review. CyberPsychology and Behavior. 2004;7(5):497–510.View ArticlePubMedGoogle Scholar
- Ryan P. Integrated theory of health behavior change: background and intervention development. Clinical nurse specialist CNS. 2009;23(3):161–70. quiz 71–72.View ArticlePubMedPubMed CentralGoogle Scholar
- Bassett-Gunter RL, Levy-Milne R, Naylor PJ, Symons Downs D, Benoit C, Warburton DER. Oh baby! Motivation for healthy eating during parenthood transitions: A longitudinal examination with a theory of planned behavior perspective. Int J Behav Nutr Phys Act. 2013;10:88.View ArticlePubMedPubMed CentralGoogle Scholar
- Nielsen KK, Kapur A, Damm P, de Courten M, Bygbjerg IC. From screening to postpartum follow-up - the determinants and barriers for gestational diabetes mellitus (GDM) services, a systematic review. BMC Pregnancy and Childbirth. 2014;14(1).Google Scholar
- Worsley A. Nutrition knowledge and food consumption: can nutrition knowledge change food behaviour? Asia Pac J Clin Nutr. 2002;11 Suppl 3:S579–85.View ArticlePubMedGoogle Scholar
- Wardle J, Parmenter K, Waller J. Nutrition knowledge and food intake. Appetite. 2002;34:269–75.View ArticleGoogle Scholar
- Rutherford L, Reid S. Knowledge, attitudes and motivations to health: A module of the Scottish Health Survey 2008–2011. Edinburgh: NHS Health Scotland; 2013.Google Scholar
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.