<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE root>
<article xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:ali="http://www.niso.org/schemas/ali/1.0/" article-type="research-article" dtd-version="1.2" xml:lang="en"><front><journal-meta><journal-id journal-id-type="publisher-id">Ekologiya cheloveka (Human Ecology)</journal-id><journal-title-group><journal-title xml:lang="en">Ekologiya cheloveka (Human Ecology)</journal-title><trans-title-group xml:lang="ru"><trans-title>Экология человека</trans-title></trans-title-group></journal-title-group><issn publication-format="print">1728-0869</issn><issn publication-format="electronic">2949-1444</issn><publisher><publisher-name xml:lang="en">Eco-Vector</publisher-name></publisher></journal-meta><article-meta><article-id pub-id-type="publisher-id">629001</article-id><article-id pub-id-type="doi">10.17816/humeco629001</article-id><article-categories><subj-group subj-group-type="toc-heading" xml:lang="en"><subject>ORIGINAL STUDY ARTICLES</subject></subj-group><subj-group subj-group-type="toc-heading" xml:lang="ru"><subject>ОРИГИНАЛЬНЫЕ ИССЛЕДОВАНИЯ</subject></subj-group><subj-group subj-group-type="article-type"><subject>Research Article</subject></subj-group></article-categories><title-group><article-title xml:lang="en">Maternal correlates of spontaneous preterm birth in Kazakhstan: a matched case-control study</article-title><trans-title-group xml:lang="ru"><trans-title>Факторы риска спонтанных преждевременных родов в Казахстане: исследование случай-контроль методом подобранных пар</trans-title></trans-title-group></title-group><contrib-group><contrib contrib-type="author"><contrib-id contrib-id-type="orcid">https://orcid.org/0000-0002-8884-6523</contrib-id><contrib-id contrib-id-type="scopus">56892790400</contrib-id><name-alternatives><name xml:lang="en"><surname>Oralkhan</surname><given-names>Zhibek</given-names></name><name xml:lang="ru"><surname>Оралхан</surname><given-names>Жибек</given-names></name></name-alternatives><address><country country="KZ">Kazakhstan</country></address><bio xml:lang="en"><p>MD</p></bio><email>september_becca@hotmail.com</email><xref ref-type="aff" rid="aff1"/></contrib><contrib contrib-type="author"><contrib-id contrib-id-type="orcid">https://orcid.org/0000-0001-8643-0703</contrib-id><name-alternatives><name xml:lang="en"><surname>Sarsenova</surname><given-names>Lazzat</given-names></name><name xml:lang="ru"><surname>Сарсенова</surname><given-names>Лаззат</given-names></name></name-alternatives><address><country country="KZ">Kazakhstan</country></address><bio><p>PhD</p></bio><email>lazzat.sarsenova@kaznu.kz</email><xref ref-type="aff" rid="aff1"/></contrib><contrib contrib-type="author"><contrib-id contrib-id-type="orcid">https://orcid.org/0000-0002-7439-5573</contrib-id><name-alternatives><name xml:lang="en"><surname>Kopbayeva</surname><given-names>Maira</given-names></name><name xml:lang="ru"><surname>Копбаева</surname><given-names>Маира</given-names></name></name-alternatives><address><country country="KZ">Kazakhstan</country></address><bio xml:lang="en"><p>MD, PhD, Professor</p></bio><bio xml:lang="ru"><p>PhD, профессор</p></bio><email>m_kopbay@mail.ru</email><xref ref-type="aff" rid="aff2"/></contrib><contrib contrib-type="author"><contrib-id contrib-id-type="orcid">https://orcid.org/0000-0002-2338-8816</contrib-id><name-alternatives><name xml:lang="en"><surname>Tastambek</surname><given-names>Kuanysh</given-names></name><name xml:lang="ru"><surname>Тастамбек</surname><given-names>Куануш</given-names></name></name-alternatives><address><country country="KZ">Kazakhstan</country></address><bio xml:lang="en"><p>PhD</p></bio><email>tastambeku@gmail.com</email><xref ref-type="aff" rid="aff1"/></contrib><contrib contrib-type="author"><contrib-id contrib-id-type="orcid">https://orcid.org/0000-0002-5464-0498</contrib-id><contrib-id contrib-id-type="spin">5118-0081</contrib-id><name-alternatives><name xml:lang="en"><surname>Grjibovski</surname><given-names>Andrej M.</given-names></name><name xml:lang="ru"><surname>Гржибовский</surname><given-names>Андрей Мечиславович</given-names></name></name-alternatives><address><country country="KZ">Kazakhstan</country></address><bio><p>MD, MPhil, PhD</p></bio><email>a.grjibovski@yandex.ru</email><xref ref-type="aff" rid="aff1"/><xref ref-type="aff" rid="aff3"/><xref ref-type="aff" rid="aff4"/><xref ref-type="aff" rid="aff5"/><xref ref-type="aff" rid="aff2"/></contrib><contrib contrib-type="author"><contrib-id contrib-id-type="orcid">https://orcid.org/0000-0002-5735-9538</contrib-id><name-alternatives><name xml:lang="en"><surname>Berdalinova</surname><given-names>Akzhenis</given-names></name><name xml:lang="ru"><surname>Бердалинова</surname><given-names>Акженис</given-names></name></name-alternatives><address><country country="KZ">Kazakhstan</country></address><email>berdalinova77@mail.ru</email><xref ref-type="aff" rid="aff1"/><xref ref-type="aff" rid="aff3"/></contrib><contrib contrib-type="author"><contrib-id contrib-id-type="orcid">https://orcid.org/0000-0003-1151-5651</contrib-id><name-alternatives><name xml:lang="en"><surname>Balmagambetova</surname><given-names>Aru</given-names></name><name xml:lang="ru"><surname>Балмагамбетова</surname><given-names>Ару</given-names></name></name-alternatives><address><country country="KZ">Kazakhstan</country></address><bio xml:lang="en"><p>PhD</p></bio><bio xml:lang="ru"><p>MD, PhD</p></bio><email>aru.b.84@mail.ru</email><xref ref-type="aff" rid="aff3"/></contrib><contrib contrib-type="author"><contrib-id contrib-id-type="orcid">https://orcid.org/0000-0002-2166-3095</contrib-id><name-alternatives><name xml:lang="en"><surname>Zhurabekova</surname><given-names>Gulmira</given-names></name><name xml:lang="ru"><surname>Журабекова</surname><given-names>Гульмира</given-names></name></name-alternatives><address><country country="KZ">Kazakhstan</country></address><bio xml:lang="en"><p>MD, PhD, Associated Professor</p></bio><bio xml:lang="ru"><p>доцент</p></bio><email>zhurabekova.gulmira@kaznu.kz</email><xref ref-type="aff" rid="aff1"/><xref ref-type="aff" rid="aff3"/></contrib></contrib-group><aff-alternatives id="aff1"><aff><institution xml:lang="en">Al-Farabi Kazakh National University</institution></aff><aff><institution xml:lang="ru">Казахский национальный университет имени аль-Фараби</institution></aff></aff-alternatives><aff-alternatives id="aff2"><aff><institution xml:lang="en">Asfendiyarov Kazakh National Medical University</institution></aff><aff><institution xml:lang="ru">Казахский национальный медицинский университет имени Асфендиярова</institution></aff></aff-alternatives><aff-alternatives id="aff3"><aff><institution xml:lang="en">West Kazakhstan Marat Ospanov State Medical University</institution></aff><aff><institution xml:lang="ru">Западно-Казахстанский государственный медицинский университет имени Марата Оспанова</institution></aff></aff-alternatives><aff-alternatives id="aff4"><aff><institution xml:lang="en">Northern State Medical University</institution></aff><aff><institution xml:lang="ru">Северный государственный медицинский университет</institution></aff></aff-alternatives><aff-alternatives id="aff5"><aff><institution xml:lang="en">Northern (Arctic) Federal University</institution></aff><aff><institution xml:lang="ru">Северный (Арктический) федеральный университет</institution></aff></aff-alternatives><pub-date date-type="preprint" iso-8601-date="2024-06-13" publication-format="electronic"><day>13</day><month>06</month><year>2024</year></pub-date><pub-date date-type="pub" iso-8601-date="2023-12-28" publication-format="electronic"><day>28</day><month>12</month><year>2023</year></pub-date><volume>30</volume><issue>12</issue><issue-title xml:lang="en"/><issue-title xml:lang="ru"/><fpage>901</fpage><lpage>908</lpage><history><date date-type="received" iso-8601-date="2024-03-12"><day>12</day><month>03</month><year>2024</year></date><date date-type="accepted" iso-8601-date="2024-04-18"><day>18</day><month>04</month><year>2024</year></date></history><permissions><copyright-statement xml:lang="en">Copyright ©; 2023, Eco-Vector</copyright-statement><copyright-statement xml:lang="ru">Copyright ©; 2023, Эко-Вектор</copyright-statement><copyright-year>2023</copyright-year><copyright-holder xml:lang="en">Eco-Vector</copyright-holder><copyright-holder xml:lang="ru">Эко-Вектор</copyright-holder><ali:free_to_read xmlns:ali="http://www.niso.org/schemas/ali/1.0/"/><license><ali:license_ref xmlns:ali="http://www.niso.org/schemas/ali/1.0/">https://creativecommons.org/licenses/by-nc-nd/4.0</ali:license_ref></license></permissions><self-uri xlink:href="https://hum-ecol.ru/1728-0869/article/view/629001">https://hum-ecol.ru/1728-0869/article/view/629001</self-uri><abstract xml:lang="en"><p><bold><italic>BACKGROUND</italic></bold><bold><italic>: </italic></bold>Preterm birth (PTB) continues to be a persistent health issue that significantly impacts neonatal morbidity and mortality worldwide. In Kazakhstan, the prevalence of PTB is 7% making a substantial contribution to adverse health outcomes among infants. However, there is a lack of comprehensive research on the factors contributing to PTB in Kazakhstan.</p> <p><bold><italic>AIM</italic></bold><bold><italic>: </italic></bold>To study maternal factors associated with spontaneous PTB among Kazakh women.</p> <p><bold><italic>MATERIAL</italic></bold><bold><italic> </italic></bold><bold><italic>AND</italic></bold><bold><italic> </italic></bold><bold><italic>METHODS</italic></bold><bold><italic>: </italic></bold>A case control study was conducted in three major reproductive hospitals in Atyrau, Aktobe and Kyzylorda from October 2022 to January 2023. The sample consisted of 90 cases with singleton live spontaneous PTB and 180 controls with spontaneous full-term delivery. Bivariate associations between categorical variables were assessed by chi-squared tests. Independent variables with <italic>p</italic> &lt;0.1 in the bivariate analysis were entered into a conditional logistic regression model. Odds ratios (OR) with 95% confidence intervals (CI) were calculated.</p> <p><bold><italic>RESULTS</italic></bold><bold><italic>: </italic></bold>Maternal education, periodontitis, body mass index and a history of PTB in previous pregnancies were associated with PTB in bivariate analysis. In multivariable models, only prior PTB (OR=38.10; 95% CI: 8.34–142.00) and periodontal disease (OR=2.09; 95% CI: 1.15–3.80) were associated with an increased risk of extremely and very preterm births while higher education (OR=0.44; 95% CI: 0.19–0.98) and a history of PTB (OR=27.20; 95% CI: 5.38–137.00) were associated with moderate to late PTB.</p> <p><bold><italic>CONCLUSION</italic></bold><bold><italic>: </italic></bold>Our results are in line with the international evidence on prior PTB being the most important determinant of PTB in the index pregnancy. Moreover, our findings on the associations with periodontal disease underline the importance of a targeted, individualized and interdisciplinary antenatal care to the reduction in the prevalence of PTB.</p></abstract><trans-abstract xml:lang="ru"><p><bold>Обоснование. </bold>Преждевременные роды (ПР) остаются актуальной проблемой здравоохранения, оказывающей значительное влияние на неонатальную заболеваемость и смертность во всем мире. В Казахстане распространённость ПР составляет 7%, что вносит существенный вклад в неблагоприятные исходы в младенческом периоде. Тем не менее в Казахстане отсутствуют комплексные исследования факторов риска ПР.</p> <p><bold>Цель.</bold> Изучить факторы риска спонтанных ПР у казахских женщин.</p> <p><bold>Материал и методы.</bold> Исследование методом случай-контроль проводили в трёх крупных учреждениях родовспоможения в городов Атырау, Актобе и Кызылорда с октября 2022 по январь 2023 г. Выборка состояла из 90 женщин со спонтанными ПР и 180 — со срочными родами. В исследование включали только одноплодные беременности. Бивариантные связи между категориальными переменными оценивали с помощью критерия хи-квадрат Пирсона. Независимые переменные, связанные с исходом на уровне значимости менее 0,1 в бивариантном анализе были введены в условную логистическую регрессионную модель. Силу связи определяли с помощью отношения шансов (ОШ) с 95% доверительными интервалами (ДИ).</p> <p><bold>Результаты.</bold> Образование матери, пародонтит, индекс массы тела и наличие ПР в анамнезе были значимо связаны с ПР при проведении бивариантного анализа. В многомерных моделях только ПР в анамнезе (ОШ=38,10; 95% ДИ: 8,34–142,00) и заболевания пародонта (ОШ=2,09; 95% ДИ: 1,15–3,80) были связаны с повышенным риском ПР в срок до 32 недель. Более высокий уровень образования (ОШ=0,44; 95% ДИ: 0,19–0,98) и наличие ПР в анамнезе (ОР=27,20; 95% ДИ: 5,38–137,00) были связаны с ПР в срок от 32 до 36 недель.</p> <p><bold>Заключение.</bold> Результаты исследования не противоречат международным данным о том, что ПР в анамнезе являются наиболее сильным прогностическим фактором для ПР. Кроме того, полученные данные о сильной связи с заболеваниями пародонта подчёркивают важность целенаправленной, индивидуализированной и междисциплинарной дородовой помощи для снижения распространенности ПР.</p></trans-abstract><kwd-group xml:lang="en"><kwd>preterm birth</kwd><kwd>risk factors</kwd><kwd>pregnancy</kwd><kwd>periodontal disease</kwd><kwd>Kazakhstan</kwd></kwd-group><kwd-group xml:lang="ru"><kwd>преждевременные роды</kwd><kwd>факторы риска</kwd><kwd>беременность</kwd><kwd>заболевания пародонта</kwd><kwd>Казахстан</kwd></kwd-group><funding-group><award-group><funding-source><institution-wrap><institution xml:lang="en">Science Committee of the Republic of Kazakhstan (Grant)</institution></institution-wrap><institution-wrap><institution xml:lang="ru">Комитет по науке Республики Казахстан (грант)</institution></institution-wrap></funding-source><award-id>AP14869249</award-id></award-group><award-group><funding-source><institution-wrap><institution xml:lang="en">Ministry of Science and Higher Education of the Republic of Kazakhstan (Grant)</institution></institution-wrap><institution-wrap><institution xml:lang="ru">Министерство науки и высшего образования Республики Казахстан (грант)</institution></institution-wrap></funding-source><award-id>AP14972889</award-id></award-group></funding-group></article-meta></front><body></body><back><ref-list><ref id="B1"><label>1.</label><mixed-citation>Romero R, Espinoza J, Mazor M, Chaiworapongsa T. The preterm parturition syndrome. In: Critchley H, Bennett P, Thornton S, eds. Preterm Birth. London: RCOG Press; 2004. P. 28–60.</mixed-citation></ref><ref id="B2"><label>2.</label><mixed-citation>Goldenberg RL, Culhane JF, Iams JD, Romero R. Epidemiology and causes of preterm birth. Lancet. 2008;371(9606):75–84. doi: 10.1016/S0140-6736(08)60074-4</mixed-citation></ref><ref id="B3"><label>3.</label><mixed-citation>Vogel JP, Chawanpaiboon S, Moller AB, et al. The global epidemiology of preterm birth. Best Pract Res Clin Obstet Gynaecol. 2018;52:3–12. doi: 10.1016/j.bpobgyn.2018.04.003. Chawanpaiboon S, Vogel JP, Moller AB, et al. Global, regional, and national estimates of levels of preterm birth in 2014: a systematic review and modelling analysis. Lancet Glob Health. 2019;7(1):e37–e46. doi: 10.1016/S2214-109X(18)30451-0</mixed-citation></ref><ref id="B4"><label>4.</label><mixed-citation>Behrman RE, Butler AS, Institute of Medicine (US) Committee on Understanding Premature Birth and Assuring Healthy Outcomes, eds. Preterm Birth: Causes, Consequences, and Prevention. Washington (DC): National Academies Press (US); 2007. doi: 10.17226/11622</mixed-citation></ref><ref id="B5"><label>5.</label><mixed-citation>National Guideline Alliance (UK). Developmental follow-up of children and young people born preterm. London: National Institute for Health and Care Excellence (NICE); August 2017.</mixed-citation></ref><ref id="B6"><label>6.</label><mixed-citation>Tingleff T, Vikanes A, Räisänen S, et al. Risk of preterm birth in relation to history of preterm birth: a population-based registry study of 213 335 women in Norway. BJOG. 2022;129(6):900–907. doi: 10.1111/1471-0528.17013</mixed-citation></ref><ref id="B7"><label>7.</label><mixed-citation>Wahabi HA. Socio-economic risk factors of spontaneous preterm birth among Saudi women: A case-control study. Int J Women's Health Reproduct Sci. 2019;7(3):276–280. doi: 10.15296/ijwhr.2019.46</mixed-citation></ref><ref id="B8"><label>8.</label><mixed-citation>Garcia-Subirats I, Pérez G, Rodríguez-Sanz M, et al. Neighborhood inequalities in adverse pregnancy outcomes in an urban setting in Spain: a multilevel approach. J Urban Health. 2012;89(3):447–463. doi: 10.1007/s11524-011-9648-4</mixed-citation></ref><ref id="B9"><label>9.</label><mixed-citation>Wood S, McNeil D, Yee W, et al. Neighbourhood socio-economic status and spontaneous premature birth in Alberta. Can J Public Heal. 2014;105(5):e383–e388. doi: 10.17269/cjph.105.4370</mixed-citation></ref><ref id="B10"><label>10.</label><mixed-citation>Ye CX, Chen SB, Wang TT, et al. Risk factors for preterm birth: a prospective cohort study. Zhongguo Dang Dai Er Ke Za Zhi. 2021;23(12):1242-1249. doi: 10.7499/j.issn.1008-8830.2108015</mixed-citation></ref><ref id="B11"><label>11.</label><mixed-citation>Son M, Miller ES. Predicting preterm birth: Cervical length and fetal fibronectin. Semin Perinatol. 2017;41(8):445–451. doi: 10.1053/j.semperi.2017.08.002</mixed-citation></ref><ref id="B12"><label>12.</label><mixed-citation>Oralkhan Z, Walia GS, Zhurabekova G, et al. The impact of periodontitis on the risk of preterm birth: Systematic review and meta-analysis. J Clin Med Kaz. 2023;20(3):56–62. doi: 10.23950/jcmk/13322</mixed-citation></ref><ref id="B13"><label>13.</label><mixed-citation>Koullali B, van Zijl MD, Kazemier BM, et al. The association between parity and spontaneous preterm birth: a population based study. BMC Pregnancy Childbirth. 2020;20(1):233. doi: 10.1186/s12884-020-02940-w</mixed-citation></ref><ref id="B14"><label>14.</label><mixed-citation>McDonald SD, Han Z, Mulla S, Beyene J. Overweight and obesity in mothers and risk of preterm birth and low birth weight infants: Systematic review and meta-analyses. BMJ. 2010;341:c3428. doi: 10.1136/bmj.c3428</mixed-citation></ref><ref id="B15"><label>15.</label><mixed-citation>Berger H, Melamed N, Davis BM, et al. Impact of diabetes, obesity and hypertension on preterm birth: Population-based study. PLoS One. 2020;15(3):e0228743. doi: 10.1371/journal.pone.0228743</mixed-citation></ref><ref id="B16"><label>16.</label><mixed-citation>Rasmussen S, Ebbing C, Irgens LM. Predicting preeclampsia from a history of preterm birth. PLoS One. 2017;12(7):e0181016. doi: 10.1371/journal.pone.0181016</mixed-citation></ref><ref id="B17"><label>17.</label><mixed-citation>Bhattacharjee E, Thiruvengadam R, Ayushi, et al. Genetic variants associated with spontaneous preterm birth in women from India: a prospective cohort study. Lancet Reg Health Southeast Asia. 2023;14:100190. doi: 10.1016/j.lansea.2023.100190</mixed-citation></ref><ref id="B18"><label>18.</label><mixed-citation>Medley N, Vogel N, Care A, Alfirevic Z. Interventions during pregnancy to prevent preterm birth: an overview of Cochrane systematic reviews. Cochrane Database Syst Rev. 2018;11(11):CD012505. doi: 10.1002/14651858.CD012505.pub2</mixed-citation></ref><ref id="B19"><label>19.</label><mixed-citation>Multiple Indicator Cluster Survey (MICS) in the Republic of Kazakhstan 2010–2011. Monitoring the Situation of Children and Women; Statistics Committee of the Ministry of National Economy of the Republic of Kazakhstan: Astana, 2012.</mixed-citation></ref><ref id="B20"><label>20.</label><mixed-citation>Lopez NJ, Smith PC, Gutierrez J. Periodontal therapy may reduce the risk of preterm low birth weight in women with periodontal disease: a randomized controlled trial. J Periodontol. 2002;73(8):911–924. doi: 10.1902/jop.2002.73.8.911</mixed-citation></ref><ref id="B21"><label>21.</label><mixed-citation>Caracho RA, Foratori-Junior GA, Fusco NDS, et al. Systemic conditions and oral health-related quality of life of pregnant women of normal weight and who are overweight. Int Dent J. 2020;70(4):287–295. doi: 10.1111/idj.12547</mixed-citation></ref><ref id="B22"><label>22.</label><mixed-citation>Woday A, Muluneh MD, Sherif S. Determinants of preterm birth among mothers who gave birth at public hospitals in the Amhara region, Ethiopia: A case-control study. PLoS One. 019;14(11):e0225060. doi: 10.1371/journal.pone.0225060</mixed-citation></ref><ref id="B23"><label>23.</label><mixed-citation>Soneji S, Beltrán-Sánchez H. Association of maternal cigarette smoking and smoking cessation with preterm birth. JAMA Netw Open. 2019;2(4):e192514. doi: 10.1001/jamanetworkopen.2019.2514</mixed-citation></ref><ref id="B24"><label>24.</label><mixed-citation>Granés L, Torà-Rocamora I, Palacio M, et al. Maternal educational level and preterm birth: Exploring inequalities in a hospital-based cohort study. PLoS One. 2023;18(4):e0283901. doi: 10.1371/journal.pone.0283901</mixed-citation></ref><ref id="B25"><label>25.</label><mixed-citation>Schmidt Morgen C, Bjørk C, Andersen PK, et al. Socioeconomic position and the risk of preterm birth — a study within the Danish National Birth Cohort. Int J Epidemiol. 2008;37(5):1109–1120. doi: 10.1093/ije/dyn112</mixed-citation></ref><ref id="B26"><label>26.</label><mixed-citation>Fuchs F, Monet B, Ducruet T, et al. Effect of maternal age on the risk of preterm birth: A large cohort study. PLoS One. 2018;13(1):e0191002. doi: 10.1371/journal.pone.0191002</mixed-citation></ref><ref id="B27"><label>27.</label><mixed-citation>Ananth CV, Peltier MR, Getahun D, et al. Primiparity: an “intermediate” risk group for spontaneous and medically indicated preterm birth. J Matern Fetal Neonatal Med. 2007;20(8):605–611. doi: 10.1080/14767050701451386</mixed-citation></ref><ref id="B28"><label>28.</label><mixed-citation>Himalatha VT, Manigandan T, Sarumathi T, et al. Dental considerations in pregnancy-a critical review on the oral care. J Clin Diagn Res. 2013;7(5):948–953. doi: 10.7860/JCDR/2013/5405.2986</mixed-citation></ref><ref id="B29"><label>29.</label><mixed-citation>Ramos-E-Silva M, Martins NR, Kroumpouzos G. Oral and vulvovaginal changes in pregnancy. Clin Dermatol. 2016;34(3):353-358. doi: 10.1016/j.clindermatol.2016.02.007</mixed-citation></ref><ref id="B30"><label>30.</label><mixed-citation>Wu M, Chen S-W, Jiang S-Y. Relationship between gingival inflammation and pregnancy. Mediators Inflammation. 2015;2015:623427. doi: 10.1155/2015/623427</mixed-citation></ref><ref id="B31"><label>31.</label><mixed-citation>Fakheran O, Saied-Moallemi Z, Khademi A, Sahebkar A. Oral health-related quality of life during pregnancy: a systematic review. Curr Pharm Des. 2020;26(32):4014–4021. doi: 10.2174/1381612826666200523171639</mixed-citation></ref><ref id="B32"><label>32.</label><mixed-citation>Bobetsis YA, Graziani F, Gürsoy M, Madianos PN. Periodontal disease and adverse pregnancy outcomes. Periodontol 2000. 2020;83(1):154–174. doi: 10.1111/prd.12294</mixed-citation></ref><ref id="B33"><label>33.</label><mixed-citation>Melve KK, Skjaerven R, Gjessing HK, Oyen N. Recurrence of gestational age in sibships: implications for perinatal mortality. Am J Epidemiol. 1999;150(7):756–762. doi: 10.1093/oxfordjournals.aje.a010078</mixed-citation></ref><ref id="B34"><label>34.</label><mixed-citation>Phillips C, Velji Z, Hanly C, Metcalfe A. Risk of recurrent spontaneous preterm birth: a systematic review and meta-analysis. BMJ Open. 2017;7(6):e015402. doi: 10.1136/bmjopen-2016-015402</mixed-citation></ref><ref id="B35"><label>35.</label><mixed-citation>Mazaki-Tovi S, Romero R, Kusanovic JP, et al. Recurrent preterm birth. Semin Perinatol. 2007;31(3):142–158. doi: 10.1053/j.semperi.2007.04.001</mixed-citation></ref><ref id="B36"><label>36.</label><mixed-citation>Adams MM, Elam-Evans LD, Wilson HG, Gilbertz DA. Rates of and factors associated with recurrence of preterm delivery. JAMA. 2000;283(12):1591–1596. doi: 10.1001/jama.283.12.1591</mixed-citation></ref><ref id="B37"><label>37.</label><mixed-citation>Ananth CV, Getahun D, Peltier MR, et al. Recurrence of spontaneous versus medically indicated preterm birth. Am J Obstet Gynecol. 2006;195(3):643–650. doi: 10.1016/j.ajog.2006.05.022</mixed-citation></ref><ref id="B38"><label>38.</label><mixed-citation>Mercer BM, Goldenberg RL, Moawad AH, et al. The Preterm Prediction Study: effect of gestational age and cause of preterm birth on subsequent obstetric outcome. Am J Obstet Gynecol. 1999;181(5 Pt 1):1216–1221. doi: 10.1016/s0002-9378(99)70111-0</mixed-citation></ref><ref id="B39"><label>39.</label><mixed-citation>Langhoff-Roos J, Krebs L, Klungsoyr K, et al. The Nordic medical birth registers — a potential goldmine for clinical research. Acta Obstet Gynecol Scand. 2014;93(2):132–137. doi: 10.1111/aogs.12302</mixed-citation></ref><ref id="B40"><label>40.</label><mixed-citation>Imankulova B, Aimagambetova G, Saiddildina L, Ukybassova T. Pregnancy outcomes complicated by preterm premature rupture of membranes: retrospective review of cases in three institutions in Kazakhstan. Cent Asian J Glob Health. 2014;3(Suppl):222. doi: 10.5195/cajgh.2014.222</mixed-citation></ref></ref-list></back></article>
