Editing Preterm birth (section)

===Reducing existing risks===
Women are identified to be at increased risk for preterm birth on the basis of their past obstetrical history or the presence of known risk factors. Preconception intervention can be helpful in selected patients in a number of ways. Patients with certain uterine anomalies may have a surgical correction (i.e. removal of a [[uterine septum]]), and those with certain medical problems can be helped by optimizing medical therapies prior to conception, be it for asthma, diabetes, hypertension, and others.

====Multiple pregnancies====
In [[multiple pregnancy|multiple pregnancies]], which often result from use of [[assisted reproductive technology]], there is a high risk of preterm birth. [[Selective reduction]] is used to reduce the number of fetuses to two or three.<ref name=ACOG2017>{{cite web |title=Opinion Number 719: Multifetal Pregnancy Reduction |url=https://www.acog.org/Clinical-Guidance-and-Publications/Committee-Opinions/Committee-on-Ethics/Multifetal-Pregnancy-Reduction |publisher=American College of Obstetricians and Gynecologists' Committee on Ethics. |date=September 2017 |access-date=26 October 2018 |archive-date=4 April 2019 |archive-url=https://web.archive.org/web/20190404072926/https://www.acog.org/Clinical-Guidance-and-Publications/Committee-Opinions/Committee-on-Ethics/Multifetal-Pregnancy-Reduction |url-status=dead }}</ref><ref name=Zipori2017>{{cite journal | vauthors = Zipori Y, Haas J, Berger H, Barzilay E | title = Multifetal pregnancy reduction of triplets to twins compared with non-reduced triplets: a meta-analysis | journal = Reproductive Biomedicine Online | volume = 35 | issue = 3 | pages = 296–304 | date = September 2017 | pmid = 28625760 | doi = 10.1016/j.rbmo.2017.05.012 | doi-access = free }}</ref><ref name=Evans2014>{{cite journal | vauthors = Evans MI, Andriole S, Britt DW | title = Fetal reduction: 25 years' experience | journal = Fetal Diagnosis and Therapy | volume = 35 | issue = 2 | pages = 69–82 | year = 2014 | pmid = 24525884 | doi = 10.1159/000357974 | doi-access = free }}</ref>

====Reducing indicated preterm birth====
A number of agents have been studied for the secondary prevention of indicated preterm birth. Trials using low-dose [[aspirin]], [[fish oil]], vitamin C and E, and calcium to reduce preeclampsia demonstrated some reduction in preterm birth only when low-dose aspirin was used.<ref name=Iams2008/> Even if agents such as calcium or [[antioxidant]]s were able to reduce preeclampsia, a resulting decrease in preterm birth was not observed.<ref name=Iams2008/>

====Reducing spontaneous preterm birth====
Reduction in activity by the mother—pelvic rest, limited work, bed rest—may be recommended although there is no evidence it is useful with some concerns it is harmful.<ref>{{cite journal | vauthors = McCall CA, Grimes DA, Lyerly AD | title = "Therapeutic" bed rest in pregnancy: unethical and unsupported by data | journal = Obstetrics and Gynecology | volume = 121 | issue = 6 | pages = 1305–1308 | date = June 2013 | pmid = 23812466 | doi = 10.1097/aog.0b013e318293f12f | s2cid = 9069311 }}</ref> Increasing medical care by more frequent visits and more education has not been shown to reduce preterm birth rates.<ref name="East2019"/> Use of nutritional supplements such as omega-3 [[polyunsaturated fatty acid]]s is based on the observation that populations who have a high intake of such agents are at low risk for preterm birth, presumably as these agents inhibit production of proinflammatory cytokines. A randomized trial showed a significant decline in preterm birth rates,<ref>
{{cite journal | vauthors = Olsen SF, Secher NJ, Tabor A, Weber T, Walker JJ, Gluud C | title = Randomised clinical trials of fish oil supplementation in high risk pregnancies. Fish Oil Trials In Pregnancy (FOTIP) Team | journal = BJOG | volume = 107 | issue = 3 | pages = 382–395 | date = March 2000 | pmid = 10740336 | doi = 10.1111/j.1471-0528.2000.tb13235.x | s2cid = 30837582 | doi-access = free }}</ref> and further studies are in the making.

=====Antibiotics=====

While antibiotics can get rid of bacterial vaginosis in pregnancy, this does not appear to change the risk of preterm birth.<ref>{{cite journal | vauthors = Brocklehurst P, Gordon A, Heatley E, Milan SJ | title = Antibiotics for treating bacterial vaginosis in pregnancy | journal = The Cochrane Database of Systematic Reviews | volume = 1 | issue = 1 | pages = CD000262 | date = January 2013 | pmid = 23440777 | pmc = 4164464 | doi = 10.1002/14651858.CD000262.pub4 }}</ref> It has been suggested that chronic chorioamnionitis is not sufficiently treated by antibiotics alone (and therefore they cannot ameliorate the need for preterm delivery in this condition).<ref name=Iams2008/>

=====Progestogens=====

[[Progestogen]]s—often given in the form of vaginal<ref>{{cite web |date=July 2017|title=Progesterone: Use in the second and third trimester of pregnancy for the prevention of preterm birth|url=https://ranzcog.edu.au/RANZCOG_SITE/media/RANZCOG-MEDIA/Women%27s%20Health/Statement%20and%20guidelines/Clinical-Obstetrics/Progesterone-use-in-the-second-and-third-trimester-(C-Obs-29b)-Review-July-2017.pdf?ext=.pdf|access-date=2021-01-29|website=The Royal Australian and New Zealand College of Obstetricians and Gynaecologists}}</ref> [[progesterone (medication)|progesterone]] or [[hydroxyprogesterone caproate]]—relax the uterine musculature, maintain cervical length, and possess anti-inflammatory properties; all of which invoke physiological and anatomical changes considered to be beneficial in reducing preterm birth. Two meta-analyses demonstrated a reduction in the risk of preterm birth in women with recurrent preterm birth by 40–55%.<ref>{{cite journal | vauthors = Dodd JM, Jones L, Flenady V, Cincotta R, Crowther CA | title = Prenatal administration of progesterone for preventing preterm birth in women considered to be at risk of preterm birth | journal = The Cochrane Database of Systematic Reviews | volume = 2015 | issue = 7 | pages = CD004947 | date = July 2013 | pmid = 23903965 | doi = 10.1002/14651858.CD004947.pub3 | s2cid = 43862120 | pmc = 11035916 }}</ref><ref>
{{cite journal | vauthors = Mackenzie R, Walker M, Armson A, Hannah ME | title = Progesterone for the prevention of preterm birth among women at increased risk: a systematic review and meta-analysis of randomized controlled trials | journal = American Journal of Obstetrics and Gynecology | volume = 194 | issue = 5 | pages = 1234–1242 | date = May 2006 | pmid = 16647905 | doi = 10.1016/j.ajog.2005.06.049 }}</ref>

Progestogen supplementation also reduces the frequency of preterm birth in pregnancies where there is a short cervix.<ref name="Iams2014">{{cite journal | vauthors = Iams JD | title = Clinical practice. Prevention of preterm parturition | journal = The New England Journal of Medicine | volume = 370 | issue = 3 | pages = 254–261 | date = January 2014 | pmid = 24428470 | doi = 10.1056/NEJMcp1103640 | s2cid = 29480873 }}</ref> A short cervix is one that is less than 25mm, as detected during a transvaginal cervical length assessment in the midtrimester.<ref>{{cite journal | vauthors = Romero R, Nicolaides KH, Conde-Agudelo A, O'Brien JM, Cetingoz E, Da Fonseca E, Creasy GW, Hassan SS | display-authors = 6 | title = Vaginal progesterone decreases preterm birth ≤ 34 weeks of gestation in women with a singleton pregnancy and a short cervix: an updated meta-analysis including data from the OPPTIMUM study | journal = Ultrasound in Obstetrics & Gynecology | volume = 48 | issue = 3 | pages = 308–317 | date = September 2016 | pmid = 27444208 | pmc = 5053235 | doi = 10.1002/uog.15953 }}</ref> However, progestogens are not effective in all populations, as a study involving twin gestations failed to see any benefit.<ref>{{cite journal |vauthors=Caritis S, Rouse D |year=2006 |title=A randomized controlled trial of 17-hydroxyprogesterone caproate (17-OHPC) for the prevention of preterm birth in twins |journal=[[American Journal of Obstetrics & Gynecology]] |volume=195 |issue=6 |pages=S2 |doi=10.1016/j.ajog.2006.10.003 |url=https://zenodo.org/record/1258694 |doi-access=free }}</ref> Despite extensive research related to progestogen effectiveness, uncertainties remain concerning types of progesterone and routes of administration.<ref>{{cite journal | vauthors = Stewart LA, Simmonds M, Duley L, Dietz KC, Harden M, Hodkinson A, Llewellyn A, Sharif S, Walker R, Wright K | display-authors = 6 | title = Evaluating progestogens for prevention of preterm birth international collaborative (EPPPIC) individual participant data (IPD) meta-analysis: protocol | journal = Systematic Reviews | volume = 6 | issue = 1 | pages = 235 | date = November 2017 | pmid = 29183399 | pmc = 5706301 | doi = 10.1186/s13643-017-0600-x | doi-access = free }}</ref>

=====Cervical cerclage=====

In preparation for [[childbirth]], the woman's [[cervix]] shortens. Preterm cervical shortening is linked to preterm birth and can be detected by ultrasonography. [[Cervical cerclage]] is a surgical intervention that places a suture around the cervix to prevent its shortening and widening. Numerous studies have been performed to assess the value of cervical cerclage and the procedure appears helpful primarily for women with a short cervix and a history of preterm birth.<ref name=Iams2014/><ref>
{{cite journal | vauthors = Berghella V, Odibo AO, To MS, Rust OA, Althuisius SM | title = Cerclage for short cervix on ultrasonography: meta-analysis of trials using individual patient-level data | journal = Obstetrics and Gynecology | volume = 106 | issue = 1 | pages = 181–189 | date = July 2005 | pmid = 15994635 | doi = 10.1097/01.AOG.0000168435.17200.53 | s2cid = 22742373 }}</ref> Instead of a prophylactic cerclage, women at risk can be monitored during pregnancy by sonography, and when shortening of the cervix is observed, the cerclage can be performed.<ref name=Iams2008/>