Emergency. 2017; 5 (1): e3 OR I G I N A L RE S E A RC H Epidemiology and Related Risk Factors of Preterm Labor as an Obstetrics Emergency Ali asghar Halimi asl1∗, Saeed Safari2, Mohsen Parvareshi Hamrah2 1. Department of Pediatrics, Shohadaye Tajrish Hospital, Shahid Beheshti University of Medical Sciences, Tehran, Iran. 2. Department of Emergency, Shohadaye Tajrish Hospital, Shahid Beheshti University of Medical Sciences, Tehran, Iran. Received: November 2015; Accepted: January 2016; Published online: 8 January 2017 Abstract: Introduction: Preterm birth is still a major health problem throughout the world, which results in 75% of neona- tal mortality. Preterm labor not only inflicts financial and emotional distress, it may also lead to permanent dis- ability. The present study was conducted to determine therelated risk factors andpreventive measuresof preterm labor. Methods: This retrospective cross-sectional study assessed all preterm labors, as well as an equal number of term labors, during seven years, at an educational hospital. Probable risk factors of preterm labor were col- lected using medical profiles of participants by the aid of a pre-designed checklist. Significant related factors of preterm laborwere used for multivariate logistic regression analysis with SPSS 21.0. Results: 810 cases with the mean age of 28.33 ± 6.1 years were evaluated (48.7% preterm). Multipartite; fetal anomaly; prenatal care; smok- ing; not consuming folic acid and iron supplements; in vitro fertilization; history of infertility, caesarian section, trauma, systemic disease, and hypertension; amniotic fluid leak; rupture of membranes; cephalic presentation; vaginal bleeding; placenta decolman; oligohydramnios; pre-eclampsia; chorioamnionitis; uterine abnormali- ties; cervical insufficiency; intercourse during the previous week; short time since last delivery; and mother’s weight significantly correlated with preterm labor. Conclusion: Based on the results of the present study, in- tercourse during the previous week, multipartite, short time from last delivery, preeclampsia, fetal anomaly, rupture of membranes, hypertension, and amniotic fluid leak, respectively, were risk factors for preterm labor. On the other hand, iron consumption, cephalic presentation, systematic disease, history of caesarian section, prenatal care, and mother’s weight could be considered as protective factors. Keywords: Premature birth; infant, premature; obstetric labor, premature; fetal membranes, premature rupture; emergen- cies © Copyright (2017) Shahid Beheshti University of Medical Sciences Cite this article as: Halimi asl AA, Safari S, Parvareshi Hamrah M. Epidemiology and Related Risk Factors of Preterm Labor as an Obstetrics Emergency. 2017; 5(1): e3. 1. Introduction P reterm labor is an obstetrics emergency and a threat to population health. 75% of infant mortality is related to preterm labor (1, 2). Preterm labor not only inflicts financial and emotional distress on the family, it may also lead to permanent disability (physical or neural damages) in infants. Approximately one-third of preterm labor survivors suffer from severe long-term neurological disabilities, such as cerebral palsy or mental retardation (3). Furthermore, preterm infants carry increased risk of a range of neurodevel- ∗Corresponding Author: Ali asghar Halimi asl; Pediatrics Department, Shoha- daye Tajrish Hospital, Shardari Street, Tajrish Square, Tehran, Iran. Tel: 00989121592797, Email: aliasgharhalimiasl@yahoo.com. opmental impairments and disabilities including behavioral problems, school learning difficulties, chronic lung disease, retinopathy of prematurity, hearing impairment, and lower growth attainment (4). Over the last two decades, preterm birth rate has remained unchanged or even risen in most countries, despite the increased understanding of possible risk factors and their pathological mechanisms (5-7). Al- though neonatal mortality rate has fallen globally between 1990 and 2009 (8), the absolute number and rate of preterm births has increased during this period. Preterm birth was the second leading cause of death in children under 5 years old (9). In 2013, preterm birth rate in Germany, Brazilan- dUnited States were 8.7%, 10.7 and 12%, respectively (10, 11). The vast majority (85%) of global preterm births occur in Asia and Africa, where health systems are weak and inade- This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: www.jemerg.com aliasgharhalimiasl@yahoo.com AA. Halimi Asl et al. 2 quate (12, 13). In Iran incidence of preterm labor was 7.2% in Tehran, 5.5% in Shiraz, and 8.4% in Khorramabad (14-16). Al- though in most cases preterm births occur idiopathically, fe- tal, uterine, and placental factors as well as maternal chronic diseases, can affect preterm birth (17). In the USA, 70% of preterm births were idiopathic and the rest were due to pre- eclampsia (50%), fetal distress (25%) and abruption (25%) (18). In another study, preterm multifetal pregnancies and hypertension were introduced as the major factors affecting preterm birth (19). In order to determine the incidence and etiologic factors of preterm labor, the present study was con- ducted on newborns at the obstetrics emergency department of Shohadaye Tajrish Hospital with a view to identifying pre- ventive measures. 2. Methods 2.1. Study design and setting This retrospective cross-sectional study assessed all preterm labors during seven years, from March 2008 until March 2015, at Shohadaye Tajrish Hospital, Tehran, Iran, by normal vaginal delivery or cesarean section, using census method. An equal number of term labors were selected by simple ran- dom sampling as the control group. The study protocol was approved by the Ethical Committee of Shahid Beheshti Uni- versity of Medical Sciences. The researchers adhered to the principles of Helsinki Declaration, as well as confidentiality of patient data and patient rights. 2.2. Data gathering Probable risk factors of preterm labor such as: mother’s age, weight, body mass index, and job; type of delivery (natural or caesarian section), baby’s sex and weight; apgar score at 1 and 5 minutes; multi-partite; fetal abnormalities;prenatal care; smoking, alcohol, and opium abuse; history of folic acid, metformin, and iron consumption; history of in vitro fertilization, infertility, abortion, preterm delivery, trauma, vaginal bleeding, intra uterine fetal death (IUFD), dental in- fection, respiratory infection, and caesarian section; amni- otic fluid leak; rupture of membranes; cephalic presentation; vaginal infection; placenta decolman; placenta praevia; poly- hydramnios; oligohydramnios; urinary tract infection; sys- temic disease; anemia; hypertension; preeclampsia; eclamp- sia; chorioamnionitis; uterine abnormalities, cervical insuf- ficiency; placental insufficiency; polycystic ovary; history of intercourse during the previous week; and timefrom last de- livery were collected using medical profiles of participants by the aid of a pre-designed checklist. Incomplete patient files were excluded. Short time from last delivery was considered to be 1 year. 2.3. Statistical analysis The data were analyzed with SPSS software version 21.0. Qualitative data were reported as mean ± standard devia- tion and quantitative ones as frequency and percentage. Fre- quency of all risk factors were compared between the two groups (preterm and term) using chi square and Fisher’s ex- act tests. Multivariate logistic regression analysis was applied to independent statistically significant factors for developing a predictive model and odds ratio (OR) of each risk factor was calculated. P value under 0.05 was considered significant. 3. Results: 810 cases with the mean age of 28.33 ± 6.1 (14 -64) years were evaluated (48.7% preterm). Table 1 depicts baseline charac- teristics of the studied patients. Among the studied risk fac- tors, multipartite (p < 0.001), fetal anomaly (p = 0.022), prena- tal care (p = 0.005), smoking (p = 0.004), not consuming folic acid (p = 0.004), not consuming iron supplements (p < 0.001), in vitro fertilization (p = 0.014), history of infertility (p = 0.005), amniotic fluid leak (p < 0.001), rupture of membranes (p < 0.001), history of caesarian section (p < 0.001), cephalic presentation (p < 0.001), history of trauma (p = 0.015), vagi- nal bleeding (p < 0.001), placenta decolman (p = 0.003), oligohydramnios (p < 0.001), history of systemic disease (p < 0.001), history of hypertension (p = 0.006), pre-eclampsia (p = 0.001), chorioamnionitis (p = 0.003), uterine abnormalities (p = 0.034), cervical insufficiency (p = 0.001), intercourse during the previous week (p < 0.001), short time since last delivery (p = 0.040), and mother’s weight (p = 0.012) significantly cor- related with higher risk of preterm labor. Table 3 shows the results of multivariate logistic regression analysis.Intercourse during the previous week (OR: 23.1), multipartite (OR: 21.8), short time from last delivery (OR: 4.8), pre-eclampsia (OR:4.7 ), fetal anomaly (OR:3.6), rupture of membranes (OR:3.5), hypertension (OR:3.3), and amniotic fluid leak (OR:2.1), re- spectively, were risk factors andiron consumption (OR:0.3), cephalic presentation (OR:0.4), systematic disease (OR:0.6), history of caesarian section (OR: 0.6), prenatal care (OR:0.6), and mother’s weight (OR:0.98), respectively, were preventive factors of preterm labor. 4. Discussion Based on the findings of the present study, indepen- dent related factors ofpreterm labor were multipartite, fetal anomaly, prenatal care, smoking, not consuming folic acid, not consuming iron supplements, in vitro fertilization, his- tory of infertility, amniotic fluid leak, rupture of membranes, history of caesarian section, cephalic presentation, history of trauma, vaginal bleeding, placenta decolman, oligohy- dramnios, history of systemic disease, history of hyperten- This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: www.jemerg.com 3 Emergency. 2017; 5 (1): e3 Table 1: Baseline characteristics of studied patients based on age of delivery Variable Term Preterm P value Age (year) 28.25 ± 5.9 28.37 ± 6.34 0.766 Weight (Kg) 76.38 ± 13.11 73.78 ± 14.19 0.012 Job Home keeper 319 (46.9) 361 (53.1) 0.626 Employee 7 (50) 7 (50) Type of delivery Natural 302 (54) 257 (46) 0.002 Caesarian section 101 (42.8) 135 (57.2) Baby’s Sex Boy 205 (46.8) 233 (53.2) 0.065 Girl 195 (55.1) 159 (44.9) Baby’s weight (gram) 3184 ± 542 2080 ± 1012 < 0.001 Apgar (1t h minute) 7.1 ± 2.3 5.7 ± 3.0 0.076 Apgar (5t h minute) 8.9 ± 0.6 7.9 ± 2.4 < 0.001 Data are presented as mean ± standard deviation or number (%). sion, preeclampsia, chorioamnionitis, uterine abnormalities, cervical insufficiency, intercourse during the previous week, short time since last delivery, and mother’s weight. Inter- course during the previous week, multipartite, short time from last delivery, preeclampsia, fetal anomaly, rupture of membranes, hypertension, and amniotic fluid leak, respec- tively, were risk factors for preterm labor. On the other hand, iron consumption, cephalic presentation, systematic dis- ease, history of caesarian section, prenatal care, and mother’s weight could be considered as protective factors. Preterm labor, as mentioned before, is a major obstetric and pedi- atric challenge because it is a common, persistent, and often devastating condition with considerable medical, economic, emotional, and social impact (20). It is thought to be a syn- drome initiated by multiple mechanisms, consisting of in- fection or inflammation, uteroplacental ischaemia or haem- orrhage, uterine overdistension, stress, and other immuno- logically mediated processes. However, adefined mecha- nism cannot be established in most cases (21). Despite ad- vancesin understanding risk factors and mechanisms related to preterm labor, the preterm labor rate has risen in most industrialized countries. In the USA, preterm labor rate in- creased from 9.5% in 1981 to 12.7% in 2005 (22, 23). In the present study, low maternal weight has increased the risk of preterm labor, while in retrospective studies, this factor weakly correlated with preterm birth (24-26). Although most of the term births were via natural delivery and most of the preterm laborsvia caesarian delivery, no significant relation- ship was found. The mean age of mothers with preterm la- borin this study, were the same as mothers with term infants, while the incidence of prematurity in different studies was greater in old mothers (27, 28). Several studies have demon- strated that adequate utilization of pre-natal care is accom- panied with improved birth weights and lower risk of preterm birth. On the other hand, inadequate pre-natal care is often referred to as a risk factor for poor pregnancy outcomes. In our study, women who had nowell-designed pre-natal care program, were atrisk for preterm labor (29, 30). Infections and vaginosis are well-known risk factors for preterm birth. In a study, presence of bacterial vaginosis at 28 weeks ges- tation was associated with an increased risk of spontaneous preterm birth (31). Nevertheless, these factors were not as- sociated with preterm birth in our study. Antibiotic ther- apy could either eliminate infections or modify their effects on pregnancy outcome (32-34). Smoking has been linked to preterm labor, and in this study this factor hadan asso- ciation with it (35, 36). Although sexual activity, particu- larly intercourse, during pregnancy has been connected to preterm labor, because of direct effects of semen on initiating preterm labor or alteration of vaginal pH, there is evidence that shows sexual activity during pregnancy is not associ- ated with preterm birth. In this study, intercourse during the previous week affected preterm birth (37). High levels of al- cohol consumption during pregnancy have obvious adverse effects on fetal development, but in this project there is no consistency between use of alcohol and chance of preterm birth (38). Various studies have suggested lower rates of preterm birth in women taking dietary supplements (39). Di- etary supplements taken before, but not after conception, were linked with a reduced rate of preterm birth; however, a placebo-controlled trial of vitamin supplementsin women before conception and 2 months after pregnancy, reported no effect on preterm birth rate (40, 41). Our results showed that folic acid and iron consumption significantly decrease the rate of preterm birth. Preterm rupture of fetal mem- branes leads to 30% of preterm births in industrialized coun- tries. Management, consists of maternal and fetal surveil- lance for labor, infection, and abruption, and administration This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: www.jemerg.com AA. Halimi Asl et al. 4 Table 2: Comparison of studied risk factors of preterm delivery between term and pre term pregnancy Risk factor Term n (%) Preterm n (%) P value Multipartite Yes 3 (6.7) 42 (93.3) < 0.001 No 403 (53) 357 (47) Fetal anomaly Yes 8 (29.6) 19 (70.4) 0.022 No 398 (51.2) 380 (48.8) Prenatal care Yes 159 (56.8) 121 (43.2) 0.005 No 247 (47) 278 (53) Smoking Yes 0 (0) 8 (100) 0.004 No 406 (50.9) 391 (49.1) Alcohol usage Yes 0 (0) 1 (100) 0.496 No 406 (50.5) 398 (49.9) Opium usage Yes 4 (28.6) 10 (71.4) 0.083 No 402 (50.8) 389 (49.2) Folic acidconsumption Yes 149 (57.3) 111 (42.7) 0.004 No 257 (47.2) 288 (52.8) Metforminconsumption Yes 5 (62.5) 3 (37.5) 0.372 No 401 (50.3) 396 (49.7) Iron consumption Yes 371 (55.1) 302 (44.9) < 0.001 No 35 (26.5) 97 (73.5) In vitro fertilization Yes 6 (26.1) 17 (73.9) 0.014 No 400 (51.2) 382 (48.8) History of infertility Yes 26 (35.6) 47 (64.4) 0.005 No 380 (51.9) 352 (48.1) History of abortion Yes 71 (51.1) 68 (48.9) 0.471 No 335 (20.3) 331 (49.7) History of preterm delivery Yes 8 (36.4) 14 (63.6) 0.131 No 398 (50.8) 385 (49.2) History of IUFD Yes 8 (36.4) 14 (63.6) 0.131 No 398 (50.8) 385 (49.2) Amniotic fluid leak Yes 79 (33.3) 158 (66.7) <0.001 No 327 (57.6) 241 (42.4) Rupture of membranes Yes 30 (22.9) 101 (77.1) < 0.001 No 376 (55.8) 298 (44.2) History of caesarian section Yes 142 (65.1) 76 (34.9) < 0.001 No 264 (45) 323 (55) Cephalic presentation Yes 343 (56.6) 263 (43.3) < 0.001 No 63 (31.7) 136 (68.3) History of trauma Yes 3 (20.3) 12 (80) 0.015 No 403 (51) 387 (49) IUFD: Intrauterine fetal death. Continued on next page This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: www.jemerg.com 5 Emergency. 2017; 5 (1): e3 Table 2: Comparison of studied risk factors of preterm delivery between term and pre term pregnancy Risk factor Term n (%) Preterm n (%) P value History of surgery Yes 34 (54) 29 (46) 0.326 No 372 (50.1) 370 (49.9) Vaginal bleeding Yes 6 (18.8) 26 (81.3) < 0.001 No 400 (51.7) 373 (48.3) Vaginal infection Yes 5 (35.7) 9 (64.3) 0.200 No 401 (50.7) 390 (49.3) Placenta decolman Yes 3 (16.7) 15 (83.3) 0.003 No 403 (51.2) 384 (48.8) Placenta praevia Yes 4 (40) 6 (60) 0.365 No 402 (50.6) 393 (49.4) Polyhydramnios Yes 3 (37.5) 5 (62.5) 0.353 No 403 (50.6) 394 (49.4) Oligohydramnios Yes 12 (25) 36 (75) < 0.001 No 394 (52) 363 (48) Urinary tract infection Yes 65 (56.5) 50 (43.5) 0.095 No 341 (49.4) 349 (50.6) Systemic disease Yes 133 (60.2) 88 (39.8) < 0.001 No 273 (46.7) 311 (53.3) Anemia Yes 31 (51.7) 29 (48.3) 0.475 No 375 (50.3) 370 (49.7) History of hypertension Yes 58 (40.6) 85 (59.4) 0.006 No 348 (52.6) 314 (47.4) Preeclampsia Yes 13 (27.7) 34 (72.3) 0.001 No 393 (51.8) 385 (48.2) Eclampsia Yes 1 (20) 4 (80) 0.181 No 405 (50.6) 395 (49.4) Chorioamnionitis Yes 1 (8.3) 11 (91.7) 0.003 No 405 (51.1) 388 (48.9) Uterine abnormalities Yes 6 (28.6) 15 (71.4) 0.034 No 400 (51) 384 (49) Cervical insufficiency Yes 0 (0) 10 (100) 0.001 No 406 (51.1) 389 (48.9) Placental insufficiency Yes 0 (90) 3 (10) 0.121 No 406 (50.6) 396 (49.4) Polycystic ovary Yes 1 (33.3) 2 (66.7) 0.493 No 405 (50.5) 397 (49.5) Body mass index Yes 12 (63.2) 7 (36.8) 0.187 No 394 (50.1) 392 (49.9) Intercourse during the previous week Yes 1 (6.3) 15 (93.8) < 0.001 No 405 (51.3) 384 (48.7) Continued on next page This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: www.jemerg.com AA. Halimi Asl et al. 6 Table 2: Comparison of studied risk factors of preterm delivery between term and pre term pregnancy Risk factor Term n (%) Preterm n (%) P value Short time since last delivery Yes 7 (30.4) 16 (69.6) 0.040 No 399 (51) 383 (49) History of dental infection Yes 1 (14.3) 6 (85.7) 0.59 No 405 (50.8) 393 (49.2) History of respiratory infection Yes 2 (50) 2 (500) 0.681 No 404 (50.4) 397 (49.6) IUFD: intrauterine fetal death. Table 3: The results of multivariate logistic regression analysis Variable Odds ratio (95% CI*) P value Intercourse during the previous week 23.1 (2.7-194.2) 0.004 Multipartite 21.8 (4.8-97.9) <0.001 Short time from last delivery 4.8 (1.4-16.2) 0.012 Preeclampsia 4.7 (1.9-11.6) 0.001 Fetal anomaly 3.6 (1.1-11.2) 0.024 Rupture of membranes 3.5 (2-6.2) <0.001 Hypertension 3.3 (1.9-5.5) <0.001 Amniotic fluid leak 2.1 (1.4-3.4) 0.001 Mother’s Weight 0.98 (0.96-0.99) 0.005 Prenatal care 0.6 (0.04-0.09) 0.036 History of caesarian section 0.6 (0.4-0.9) 0.020 Systematic Disease 0.6 (0.4-0.9) 0.010 Cephalic presentation 0.4 (0.2-0.6) <0.001 Iron consumption 0.3 (0.2-0.6) <0.001 CI∗: confidence interval. of corticosteroids or antibiotics (42, 43). Ruptures of the fetal membranes are remarkably seen in preterm birth. The avail- ability of medical reproductive techniques has increased the number of multiple pregnancies. In addition, multiple preg- nancies resulting from reproductive medical treatments are more common in women of advanced maternal age (44). The preterm birth rate for multiple pregnancies stands at 40-60% (45). Multipartite and in vitro fertilization directly correlated with preterm birth. In our study, pre-eclampsia was 72.3% in preterm labor and 27.7% in term labors. In our study, history of chronic hypertension was seen in 59.4% of mothers with preterm labor and 40.6% in mothers with term labor. In other studies the most common maternal disease was hyperten- sion (16). Using the results of this study and similar onesto eliminate the risk factors and reinforcethe protective factors would be helpful in decreasing the rate of preterm labor and its human and social burden. Yet, for accurately determin- ing these factors, studies with better design, such as cohort studies, with proper follow-up period and large study pop- ulation, are needed. Since the studied hospital is a referral center for these patients, it represents the general population of the country to a great extent. Still, the final decision re- garding factors definitely affecting pre-term labor should be made after further studies. 5. Conclusion Based on the results of the present study, intercourse during the previous week, multipartite, short time from last delivery, preeclampsia, fetal anomaly, rupture of membranes, hyper- tension, and amniotic fluid leak, respectively, were risk fac- tors for preterm labor. On the other hand, iron consumption, cephalic presentation, systematic disease, history of caesar- ian section, prenatal care, and mother’s weight could be con- sidered as protective factors. 6. Appendix 6.1. Acknowledgements We would like to thank Dr. M Afrakhte, specialist of peri- natology, medical staff of emergency department, and the manager of medical recordsunit of Shohadaye Tajrish Hos- pital who provided help for this study. This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: www.jemerg.com 7 Emergency. 2017; 5 (1): e3 6.2. Authors Contributions All authors passed four criteria for authorship contribution based on recommendations of the International Committee of Medical Journal Editors. 6.3. Funding Support None 6.4. Conflict of Interest None References 1. Kliegman RM, Behrman R, Jenson H. Stanton B. Nel- son textbook of pediatrics. Germany: Elsevier Health Sci- ences; 2007. 2. Cunningham F, Leveno K, Bloom S, Hauth J, Rouse D. Spong CY Williams Obstetrics. USA: The McGraw-Hill Companies, Inc. Medical Publishing Division; 2010. 3. Lawn JE, Cousens S, Zupan J, Team LNSS. 4 mil- lion neonatal deaths: when Where Why The Lancet. 2005;365(9462):891-900. 4. Saigal S, Doyle LW. An overview of mortality and sequelae of preterm birth from infancy to adulthood. The Lancet. 2008;371(9608):261-9. 5. Blencowe H, Cousens S, Oestergaard MZ, Chou D, Moller A-B, Narwal R, et al. National, regional, and worldwide estimates of preterm birth rates in the year 2010 with time trends since 1990 for selected coun- tries: a systematic analysis and implications. The Lancet. 2012;379(9832):2162-72. 6. Langhoff-Roos J, Kesmodel U, Jacobsson B, Rasmussen S, Vogel I. Spontaneous preterm delivery in primiparous women at low risk in Denmark: population based study. Bmj. 2006;332(7547):937-9. 7. Norman JE, Morris C, Chalmers J. The effect of chang- ing patterns of obstetric care in Scotland (1980-2004) on rates of preterm birth and its neonatal consequences: perinatal database study. PLoS medicine. 2009;6(9):1009. 8. Oestergaard MZ, Inoue M, Yoshida S, Mahanani WR, Gore FM, Cousens S, et al. Neonatal mortality levels for 193 countries in 2009 with trends since 1990: a system- atic analysis of progress, projections, and priorities. PLoS Med. 2011;8(8):e1001080. 9. Organization WH. Born too soon: the global action re- port on preterm birth. 2012. 10. Zeitlin J, Szamotulska K, Drewniak N, Mohangoo A, Chalmers J, Sakkeus L, et al. Preterm birth time trends in Europe: a study of 19 countries. BJOG: An International Journal of Obstetrics, Gynaecology. 2013;120(11):1356- 65. 11. Martin JA, Hamilton BE, Ventura SJ, Osterman MJ, Wil- son EC, Mathews T. Births: final data for 2010. National vital statistics reports. 2012;61(1):1-72. 12. Beck S, Wojdyla D, Say L, Betran AP, Merialdi M, Requejo JH, et al. The worldwide incidence of preterm birth: a sys- tematic review of maternal mortality and morbidity. Bul- letin of the World Health Organization. 2010;88(1):31-8. 13. Lawn JE, Gravett MG, Nunes TM, Rubens CE, Stanton C. Global report on preterm birth and stillbirth (1 of 7): definitions, description of the burden and opportu- nities to improve data. BMC pregnancy and childbirth. 2010;10(Suppl 1):S1. 14. Afrakhteh M, Ebrahimi S, VALAEI N. PREVALENCE OF PRETERM DELIVERY AND ITS RELATED FACTORS IN FEMALES REFERRING TO SHOHADA TAJRISH HOSPI- TAL, 1995-99. 2002. 15. Pourarian S, Vafafar A, Zareh Z. The incidence of prema- turity in the Hospital of Shiraz university of medical sci- ences and health services, 1999. Razi Journal of Medical Sciences. 2002;9(28):19-25. 16. MOHSENZADEH A, SAKET S, KARIMI A. Prevalence of preterm neonates and risk factors. 2011. 17. Gomella T. Polycythemia and hyperviscocity. Dalam: Gomella TL, Cunningham MD, Eyal FG, Zenk KE, penyunting. Neonatology: management, procedures, on call problems, diseases and drugs. Edisi ke-5. NewYork: McGraw-Hill; 2004. 18. Meis PJ, Goldenberg RL, Mercer BM, Iams JD, Moawad AH, Miodovnik M, et al. The preterm prediction study: risk factors for indicated preterm births. American jour- nal of obstetrics and gynecology. 1998;178(3):562-7. 19. Burke C, Morrison JJ. Perinatal factors and preterm deliv- ery in an Irish obstetric population. Journal of perinatal medicine. 2000;28(1):49-53. 20. McCormick MC. The contribution of low birth weight to infant mortality and childhood morbidity. New England journal of medicine. 1985;312(2):82-90. 21. Romero R, Espinoza J, Kusanovic JP, Gotsch F, Has- san S, Erez O, et al. The preterm parturition syndrome. BJOG: An International Journal of Obstetrics, Gynaecol- ogy. 2006;113(s3):17-42. 22. Hamilton BE, Martin JA, Ventura SJ. Births: prelim- inary data for 2005. National vital statistics reports. 2006;55(11):1-18. 23. Goldenberg RL, Rouse DJ. Prevention of premature birth. New England Journal of Medicine. 1998;339(5):313-20. 24. Kramer MS. Determinants of low birth weight: method- ological assessment and meta-analysis. Bulletin of the World Health Organization. 1987;65(5):663. 25. HEDIGER ML, SCHOLL TO, BELSKY DH, ANCES IG, SALMON RW. Patterns of weight gain in adolescent preg- nancy: effects on birth weight and preterm delivery. Ob- This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: www.jemerg.com AA. Halimi Asl et al. 8 stetrics, Gynecology. 1989;74(1):6-12. 26. Carmichael S, Abrams B, Selvin S. The pattern of maternal weight gain in women with good preg- nancy outcomes. American Journal of Public Health. 1997;87(12):1984-8. 27. Ebrahimi S, Haghbin S, PoorMahmoodi A. Incidence and etiologic factors of prematurity. 2000. 28. Heaman M, Kingston D, Chalmers B, Sauve R, Lee L, Young D. Risk Factors for Preterm Birth and Smal- lâĂŘforâĂŘgestationalâĂŘage Births among Cana- dian Women. Paediatric and perinatal epidemiology. 2013;27(1):54-61. 29. Care P. Medicaid Recipients and Uninsured Women Ob- tain Insufficient Care. Government Accounting Office (GAO), Washington DC. 1987. 30. Sokol RJ, Woolf RB, Rosen MG, Weingarden K. Risk, antepartum care, and outcome: impact of a mater- nity and infant care project. Obstetrics, Gynecology. 1980;56(2):150-6. 31. Meis PJ, Goldenberg RL, Mercer B, Moawad A, Das A, Mc- Nellis D, et al. The preterm prediction study: significance of vaginal infections. American journal of obstetrics and gynecology. 1995;173(4):1231-5. 32. Paige DM, Augustyn M, Adih WK, Witter F, Chang J. Bacterial vaginosis and preterm birth: a comprehen- sive review of the literature. Journal of Nurse-Midwifery. 1998;43(2):83-9. 33. Romero R, Mazor M. Infection and preterm labor. Clini- cal obstetrics and gynecology. 1988;31(3):553-84. 34. Holst E, Goffeng AR, Andersch B. Bacterial vaginosis and vaginal microorganisms in idiopathic premature labor and association with pregnancy outcome. Journal of clin- ical microbiology. 1994;32(1):176-86. 35. Keirse M. An evaluation of formal risk scoring for preterm birth. American journal of perinatology. 1989;6(2):226- 33. 36. Shiono PH, Klebanoff MA, Rhoads GG. Smoking and drinking during pregnancy: their effects on preterm birth. Jama. 1986;255(1):82-4. 37. Klebanoff MA, Graubard BI, Kessel SS, Berendes HW. Low birth weight across generations. Jama. 1984;252(17):2423-7. 38. Spohr H-L, Willms J, Steinhausen H-C. Prenatal alcohol exposure and long-term developmental consequences. The Lancet. 1993;341(8850):907-10. 39. Vahratian A, Siega-Riz AM, Savitz DA, Thorp JM. Multivi- tamin use and the risk of preterm birth. American journal of epidemiology. 2004;160(9):886-92. 40. Czeizel A, Dudas I, Metneki J. Pregnancy outcomes in a randomised controlled trial of periconceptional multivi- tamin supplementation. Archives of gynecology and ob- stetrics. 1994;255(3):131-9. 41. Obstetricians ACo, Gynecologists. The importance of preconception care in the continuum of womenâĂŹs healthcare. Committee Opinion No. 313. Obstet Gynecol. 2005;106(3):665-6. 42. Roberts D, Dalziel S. Antenatal corticosteroids for ac- celerating fetal lung maturation for women at risk of preterm birth (Review). Cochrane Database Syst Rev. 2006;19:CD004454. 43. Wapner RJ, Sorokin Y, Thom EA, Johnson F, Dudley DJ, Spong CY, et al. Single versus weekly courses of an- tenatal corticosteroids: evaluation of safety and effi- cacy. American journal of obstetrics and gynecology. 2006;195(3):633-42. 44. McClamrock HD, Jones HW, Adashi EY. Ovarian stimula- tion and intrauterine insemination at the quarter centen- nial: implications for the multiple births epidemic. Fer- tility and sterility. 2012;97(4):802-9. 45. Ferraretti A, Goossens V, De Mouzon J, Bhattacharya S, Castilla J, Korsak V, et al. Assisted reproductive technology in Europe, 2008: results generated from European registers by ESHRE. Human reproduction. 2012;27(9):2571-84. This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: www.jemerg.com Introduction Methods Results: Discussion Conclusion Appendix References