Editing Preterm birth (section)

====Factors during pregnancy====
Medications during pregnancy, living conditions, air pollution, smoking, illicit drugs or alcohol, infection, or physical trauma may also cause a preterm birth.

Air pollution: Living in an area with a high concentration of air pollution is a major risk factor for preterm labor, including living near major roadways or highways where vehicle emissions are high from traffic congestion or are a route for diesel trucks that tend to emit more pollution.<ref>{{Cite journal| vauthors = Currie J |date=October 2009|title=Traffic Congestion and Infant Health: Evidence from E-ZPass|url=https://www.nber.org/papers/w15413.pdf|journal=National Bureau of Economic Research}}</ref><ref>{{Cite news|url=https://www.cbc.ca/news/technology/air-pollution-study-1.5339472|title=Harmful air pollution 'definitely too high for the public' near city roads, study suggests| vauthors = Chung E |date=30 October 2019|publisher=CBC News|access-date=2 November 2019}}</ref><ref name="Kor2017" />

The use of [[fertility medication]] that stimulates the ovary to release multiple eggs and of [[In vitro fertilisation|IVF]] with [[embryo transfer]] of multiple embryos has been implicated as a risk factor for preterm birth. Often labor has to be induced for medical reasons; such conditions include [[high blood pressure]],<ref name="Goldenberg1998">{{cite journal | vauthors = Goldenberg RL, Iams JD, Mercer BM, Meis PJ, Moawad AH, Copper RL, Das A, Thom E, Johnson F, McNellis D, Miodovnik M, Van Dorsten JP, Caritis SN, Thurnau GR, Bottoms SF | display-authors = 6 | title = The preterm prediction study: the value of new vs standard risk factors in predicting early and all spontaneous preterm births. NICHD MFMU Network | journal = American Journal of Public Health | volume = 88 | issue = 2 | pages = 233–238 | date = February 1998 | pmid = 9491013 | pmc = 1508185 | doi = 10.2105/AJPH.88.2.233 }}</ref> [[pre-eclampsia]],<ref name="Banhidy2007">
{{cite journal | vauthors = Bánhidy F, Acs N, Puhó EH, Czeizel AE | title = Pregnancy complications and birth outcomes of pregnant women with urinary tract infections and related drug treatments | journal = Scandinavian Journal of Infectious Diseases | volume = 39 | issue = 5 | pages = 390–397 | year = 2007 | pmid = 17464860 | doi = 10.1080/00365540601087566 | s2cid = 5159387 }}</ref> maternal diabetes,<ref name="Rosenberg2005">{{cite journal | vauthors = Rosenberg TJ, Garbers S, Lipkind H, Chiasson MA | title = Maternal obesity and diabetes as risk factors for adverse pregnancy outcomes: differences among 4 racial/ethnic groups | journal = American Journal of Public Health | volume = 95 | issue = 9 | pages = 1545–1551 | date = September 2005 | pmid = 16118366 | pmc = 1449396 | doi = 10.2105/AJPH.2005.065680 }}</ref> asthma, thyroid disease, and heart disease.

Certain medical conditions in the pregnant mother may also increase the risk of preterm birth. Some women have anatomical problems that prevent the baby from being carried to term. These include a weak or short [[cervix]] (the strongest predictor of premature birth).<ref>
{{cite journal | vauthors = To MS, Skentou CA, Royston P, Yu CK, Nicolaides KH | title = Prediction of patient-specific risk of early preterm delivery using maternal history and sonographic measurement of cervical length: a population-based prospective study | journal = Ultrasound in Obstetrics & Gynecology | volume = 27 | issue = 4 | pages = 362–367 | date = April 2006 | pmid = 16565989 | doi = 10.1002/uog.2773 | s2cid = 24970386 | doi-access = free }}</ref><ref name="Fonseca2007">
{{cite journal | vauthors = Fonseca EB, Celik E, Parra M, Singh M, Nicolaides KH | title = Progesterone and the risk of preterm birth among women with a short cervix | journal = The New England Journal of Medicine | volume = 357 | issue = 5 | pages = 462–469 | date = August 2007 | pmid = 17671254 | doi = 10.1056/NEJMoa067815 | s2cid = 14884358 | doi-access = free }}</ref><ref name="Romero2007">
{{cite journal | vauthors = Romero R | title = Prevention of spontaneous preterm birth: the role of sonographic cervical length in identifying patients who may benefit from progesterone treatment | journal = Ultrasound in Obstetrics & Gynecology | volume = 30 | issue = 5 | pages = 675–686 | date = October 2007 | pmid = 17899585 | doi = 10.1002/uog.5174 | s2cid = 46366053 | doi-access = free }}</ref><ref name=Goldenberg1998/> Women with vaginal bleeding during pregnancy are at higher risk for preterm birth. While bleeding in the third trimester may be a sign of [[placenta previa]] or [[placental abruption]]—conditions that occur frequently preterm—even earlier bleeding that is not caused by these conditions is linked to a higher preterm birth rate.<ref>
{{cite journal | vauthors = Krupa FG, Faltin D, Cecatti JG, Surita FG, Souza JP | title = Predictors of preterm birth | journal = International Journal of Gynaecology and Obstetrics | volume = 94 | issue = 1 | pages = 5–11 | date = July 2006 | pmid = 16730012 | doi = 10.1016/j.ijgo.2006.03.022 | s2cid = 41368575 }}</ref> Women with abnormal amounts of [[amniotic fluid]], whether too much ([[polyhydramnios]]) or too little ([[oligohydramnios]]), are also at risk.<ref name=Goldenberg2008/> [[Anxiety]] and [[Major depressive disorder|depression]] have been linked as risk factors for preterm birth.<ref name="Goldenberg2008" /><ref name="Dole2003">
{{cite journal | vauthors = Dole N, Savitz DA, Hertz-Picciotto I, Siega-Riz AM, McMahon MJ, Buekens P | title = Maternal stress and preterm birth | journal = American Journal of Epidemiology | volume = 157 | issue = 1 | pages = 14–24 | date = January 2003 | pmid = 12505886 | doi = 10.1093/aje/kwf176 | url = http://171.66.121.65/cgi/reprint/157/1/14 | url-status = dead | s2cid = 44325654 | doi-access = free | archive-url = https://web.archive.org/web/20071008202838/http://171.66.121.65/cgi/reprint/157/1/14 | archive-date = 8 October 2007 | url-access = subscription }}</ref>

The use of [[tobacco]], [[cocaine]], and excessive [[alcohol (drug)|alcohol]] during pregnancy increases the chance of preterm delivery. [[Tobacco smoking|Tobacco]] is the most commonly used drug during pregnancy and contributes significantly to low birth weight delivery.<ref>
{{cite journal | vauthors = Parazzini F, Chatenoud L, Surace M, Tozzi L, Salerio B, Bettoni G, Benzi G | title = Moderate alcohol drinking and risk of preterm birth | journal = European Journal of Clinical Nutrition | volume = 57 | issue = 10 | pages = 1345–1349 | date = October 2003 | pmid = 14506499 | doi = 10.1038/sj.ejcn.1601690 | s2cid = 27688375 | doi-access = free }}</ref> Babies with [[birth defect]]s are at higher risk of being born preterm.<ref>
{{cite journal | vauthors = Dolan SM, Gross SJ, Merkatz IR, Faber V, Sullivan LM, Malone FD, Porter TF, Nyberg DA, Comstock CH, Hankins GD, Eddleman K, Dugoff L, Craigo SD, Timor-Tritsch I, Carr SR, Wolfe HM, Bianchi DW, D'Alton ME | display-authors = 6 | title = The contribution of birth defects to preterm birth and low birth weight | journal = Obstetrics and Gynecology | volume = 110 | issue = 2 Pt 1 | pages = 318–324 | date = August 2007 | pmid = 17666606 | doi = 10.1097/01.AOG.0000275264.78506.63 | s2cid = 32544532 }}</ref>

[[Passive smoking]] and/or smoking before the pregnancy influences the probability of a preterm birth. The [[World Health Organization]] published an international study in March 2014.<ref>[[The Lancet]] 28. März 2014: [http://www.thelancet.com/journals/lancet/article/PIIS0140-6736%2814%2960082-9/abstract Effect of smoke-free legislation on perinatal and child health: a systematic review and meta-analysis]. This study is registered with PROSPERO, number CRD42013003522</ref>

Presence of [[anti-thyroid antibodies]] is associated with an increased risk preterm birth with an [[odds ratio]] of 1.9 and 95% [[confidence interval]] of 1.1–3.5.<ref>{{cite journal | vauthors = van den Boogaard E, Vissenberg R, Land JA, van Wely M, van der Post JA, Goddijn M, Bisschop PH | title = Significance of (sub)clinical thyroid dysfunction and thyroid autoimmunity before conception and in early pregnancy: a systematic review | journal = Human Reproduction Update | volume = 17 | issue = 5 | pages = 605–619 | year = 2011 | pmid = 21622978 | doi = 10.1093/humupd/dmr024 | doi-access = free }}</ref>

Intimate violence against the mother is another risk factor for preterm birth.<ref>{{cite journal | vauthors = Boy A, Salihu HM | title = Intimate partner violence and birth outcomes: a systematic review | journal = International Journal of Fertility and Women's Medicine | volume = 49 | issue = 4 | pages = 159–164 | year = 2004 | pmid = 15481481 }}</ref>

Physical trauma may case a preterm birth. The Nigerian cultural method of abdominal massage has been shown to result in 19% preterm birth among women in [[Nigeria]], plus many other adverse outcomes for the mother and baby.<ref>
{{cite journal | vauthors = Ugboma HA, Akani CI | title = Abdominal massage: another cause of maternal mortality | journal = Nigerian Journal of Medicine | volume = 13 | issue = 3 | pages = 259–262 | year = 2004 | pmid = 15532228 }}</ref> This ought not be confused with massage therapy conducted by a fully trained and certified/licensed massage therapist or by significant others trained to provide massage during pregnancy, which—in a study involving pregnant females with prenatal depression—has been shown to have numerous positive results during pregnancy, including the reduction of preterm birth, less depression, lower cortisol, and reduced anxiety.<ref>{{cite journal | vauthors = Field T, Deeds O, Diego M, Hernandez-Reif M, Gauler A, Sullivan S, Wilson D, Nearing G | display-authors = 6 | title = Benefits of combining massage therapy with group interpersonal psychotherapy in prenatally depressed women | journal = Journal of Bodywork and Movement Therapies | volume = 13 | issue = 4 | pages = 297–303 | date = October 2009 | pmid = 19761951 | pmc = 2785018 | doi = 10.1016/j.jbmt.2008.10.002 }}</ref> In healthy women, however, no effects have been demonstrated in a controlled study.