Editing Recurrent miscarriage (section)

=== Lifestyle factors ===

While lifestyle factors have been associated with increased risk for miscarriage in general, and are usually not listed as specific causes for RPL. These include cigarette smoking, caffeine intake, alcohol use, BMI, and stress.<ref name="ACOG2001">{{cite journal |year=2001 |title=Management of Early Pregnancy Loss |journal=ACOG Practice Bulletin |publisher=[[American College of Obstetricians and Gynecologists]] |volume=24 |issue=February}}</ref><ref name="Fertility and Sterility_2012_2" />

* '''Smoking:''' There is limited research that directly looks at the association of cigarette smoking and RPL. Recently, a systematic review that looked at studies evaluating the link between RPL and smoking was unable to find a significant difference in risk of recurrent pregnancy loss between people that smoke and non-smokers.<ref name="Ng_2021_2">{{cite journal | vauthors = Ng KY, Cherian G, Kermack AJ, Bailey S, Macklon N, Sunkara SK, Cheong Y | title = Systematic review and meta-analysis of female lifestyle factors and risk of recurrent pregnancy loss | journal = Scientific Reports | volume = 11 | issue = 1 | pages = 7081 | date = March 2021 | pmid = 33782474 | pmc = 8007745 | doi = 10.1038/s41598-021-86445-2 | bibcode = 2021NatSR..11.7081N }}</ref> This review did not address e-cigarettes and vaping given that the authors did not find any studies that looked into the relationship between these forms of smoking and RPL. The relationship between smoking and the risk of miscarriage has been extensively researched. According to a systematic review and meta-analysis, there is some evidence that active cigarette smoking increases the risk of miscarriage and this risk is further increased the more cigarettes that a person smokes a day.<ref name="Pineles_2014">{{cite journal | vauthors = Pineles BL, Park E, Samet JM | title = Systematic review and meta-analysis of miscarriage and maternal exposure to tobacco smoke during pregnancy | journal = American Journal of Epidemiology | volume = 179 | issue = 7 | pages = 807–23 | date = April 2014 | pmid = 24518810 | pmc = 3969532 | doi = 10.1093/aje/kwt334 | url = }}</ref> This same review highlights that according to the Surgeon General's report in 2010, research supports that smoking during pregnancy can also lead to pregnancy complications such as placental abruption, preterm delivery, and low birthweight among other maternal health risks.<ref name="Pineles_2014" /><ref>{{Citation |last1=Prevention (US) |first1=Centers for Disease Control and |title=Reproductive and Developmental Effects |date=2010 |url=https://www.ncbi.nlm.nih.gov/books/NBK53022/ |work=How Tobacco Smoke Causes Disease: The Biology and Behavioral Basis for Smoking-Attributable Disease: A Report of the Surgeon General |access-date=2023-11-15 |publisher=Centers for Disease Control and Prevention (US) |language=en |last2=Promotion (US) |first2=National Center for Chronic Disease Prevention and Health |last3=Health (US) |first3=Office on Smoking and}}</ref>
* '''Caffeine''': research regarding the association of caffeine intake and spontaneous pregnancy loss has produced inconsistent results in previous years due to the influence of multiple factors and limitations in data collection among the studies.<ref name="Chen_2016">{{cite journal | vauthors = Chen LW, Wu Y, Neelakantan N, Chong MF, Pan A, van Dam RM | title = Maternal caffeine intake during pregnancy and risk of pregnancy loss: a categorical and dose-response meta-analysis of prospective studies | journal = Public Health Nutrition | volume = 19 | issue = 7 | pages = 1233–1244 | date = May 2016 | pmid = 26329421 | pmc = 10271029 | doi = 10.1017/S1368980015002463 }}</ref> The same systematic review that looked at the relationship between cigarette smoking and RPL in 2021 found that there was no increased risk of RPL with the consumption of caffeine.<ref name="Ng_2021_2"/> There have been more recent studies that have assessed the relationship between caffeine and miscarriage. A systematic review found that coffee consumption before and during pregnancy was associated with a higher risk of pregnancy loss. The risk of pregnancy loss increased by 3% with each additional cup of coffee consumed during pregnancy. There was also an increased risk of pregnancy loss of 14-26% with the consumption of an additional 100&nbsp;mg of caffeine (coffee, tea, soda, cacao) per day during pregnancy. This increased risk was not seen if the caffeine products were consumed prior to pregnancy.<ref name="Jafari_2022">{{cite journal | vauthors = Jafari A, Naghshi S, Shahinfar H, Salehi SO, Kiany F, Askari M, Surkan PJ, Azadbakht L | display-authors = 6 | title = Relationship between maternal caffeine and coffee intake and pregnancy loss: A grading of recommendations assessment, development, and evaluation-assessed, dose-response meta-analysis of observational studies | journal = Frontiers in Nutrition | volume = 9 | pages = 886224 | date = 2022-08-09 | pmid = 36017225 | pmc = 9396037 | doi = 10.3389/fnut.2022.886224 | doi-access = free }}</ref> The harmful effects of caffeine during pregnancy can be attributed to its ability to absorb rapidly into the bloodstream and cross into the placenta, along with the slowed breakdown of caffeine that occurs during pregnancy which can expose the fetus to caffeine and its metabolites for a prolonged period of time. Caffeine consumption can also lead to maternal cardiovascular effects that reduce placental blood flow, putting the development of the fetus at risk.<ref name="Ng_2021_2"/><ref name="Chen_2016" /><ref name="Jafari_2022" />
* '''Alcohol Use:''' Prenatal exposure to alcohol has been shown to have damaging effects on the cognitive development of the fetus and has been associated with low birthweight among other features of [[Fetal alcohol spectrum disorder]]s due to its teratogenic effects.<ref>{{cite journal | vauthors = Mamluk L, Jones T, Ijaz S, Edwards HB, Savović J, Leach V, Moore TH, von Hinke S, Lewis SJ, Donovan JL, Lawlor DA, Davey Smith G, Fraser A, Zuccolo L | display-authors = 6 | title = Evidence of detrimental effects of prenatal alcohol exposure on offspring birthweight and neurodevelopment from a systematic review of quasi-experimental studies | journal = International Journal of Epidemiology | volume = 49 | issue = 6 | pages = 1972–1995 | date = January 2021 | pmid = 31993631 | pmc = 7825937 | doi = 10.1093/ije/dyz272 }}</ref><ref name="Guideline No. 405: Screening and Co">{{cite journal | vauthors = Graves L, Carson G, Poole N, Patel T, Bigalky J, Green CR, Cook JL | title = Guideline No. 405: Screening and Counselling for Alcohol Consumption During Pregnancy | journal = Journal of Obstetrics and Gynaecology Canada | volume = 42 | issue = 9 | pages = 1158–1173.e1 | date = September 2020 | pmid = 32900457 | doi = 10.1016/j.jogc.2020.03.002 | s2cid = 221571729 }}</ref> Similar to smoking and caffeine consumption, research studies assessing the relationship between alcohol use and pregnancy loss have produced inconsistent results. A systematic review that looked at several maternal lifestyle factors and the risk of recurrent pregnancy loss found no statistically significant increased risk in women that consumed any form of alcohol during pregnancy compared to those that did not.<ref name="Ng_2021_2"/> These findings are similar to a recent review that looked at alcohol intake in the first and second trimester and found no increased risk of miscarriage. The authors report that this may have been due to a limited number of studies included in the review, considering the exclusion of studies that did not differentiate trimesters or account for other external factors (such as smoking, maternal age, maternal BMI) that have been linked to pregnancy loss.<ref>{{cite journal | vauthors = Saxov KR, Strandberg-Larsen K, Pristed SG, Bruun NH, Kesmodel US | title = Maternal alcohol consumption and the risk of miscarriage in the first and second trimesters: A systematic review and dose-response meta-analysis | journal = Acta Obstetricia et Gynecologica Scandinavica | volume = 102 | issue = 7 | pages = 821–832 | date = July 2023 | pmid = 37221907 | pmc = 10333669 | doi = 10.1111/aogs.14566 }}</ref> There is evidence that in women that drink 5 or less alcoholic drinks per week, there is a 6% increased risk of miscarriage with each additional alcoholic drink consumed when the specific trimester is not specified.<ref>{{cite journal | vauthors = Sundermann AC, Zhao S, Young CL, Lam L, Jones SH, Velez Edwards DR, Hartmann KE | title = Alcohol Use in Pregnancy and Miscarriage: A Systematic Review and Meta-Analysis | journal = Alcoholism: Clinical and Experimental Research | volume = 43 | issue = 8 | pages = 1606–1616 | date = August 2019 | pmid = 31194258 | pmc = 6677630 | doi = 10.1111/acer.14124 }}</ref> Due to the inability to determine a safe range of alcohol consumption during pregnancy, multiple medical societies recommend avoiding alcohol to prevent the potential harm to the fetus.<ref name="Guideline No. 405: Screening and Co"/><ref>{{cite journal | vauthors =  | title = ACOG Committee Opinion No. 762: Prepregnancy Counseling | journal = Obstetrics and Gynecology | volume = 133 | issue = 1 | pages = e78–e89 | date = January 2019 | pmid = 30575679 | doi = 10.1097/AOG.0000000000003013 | s2cid = 264624769 }}</ref><ref>{{Cite book |url=http://www.ncbi.nlm.nih.gov/books/NBK200701/ |title=Guidelines for the Identification and Management of Substance Use and Substance Use Disorders in Pregnancy |date=2014 |publisher=World Health Organization |isbn=978-92-4-154873-1 |series=WHO Guidelines Approved by the Guidelines Review Committee |location=Geneva |pmid=24783312}}</ref>
* '''BMI''': Maternal obesity and an elevated [[Body mass index]] (BMI) has been associated with an increased risk of miscarriage, although no clear cause has been established.<ref>{{cite journal | vauthors = Metwally M, Ong KJ, Ledger WL, Li TC | title = Does high body mass index increase the risk of miscarriage after spontaneous and assisted conception? A meta-analysis of the evidence | journal = Fertility and Sterility | volume = 90 | issue = 3 | pages = 714–726 | date = September 2008 | pmid = 18068166 | doi = 10.1016/j.fertnstert.2007.07.1290 | doi-access = free }}</ref> Studies suggest that pregnancy loss could be influenced by the downstream effects of the hormonal disruption of the HPA axis and insulin resistance that can be associated with obesity, on the reproductive system disrupting the development of oocytes, embryos, or the integrity of the [[endometrium]] (uterine lining).<ref name="Eapen_2021">{{cite journal | vauthors = Eapen A, Hayes ET, McQueen DB, Beestrum M, Eyck PT, Boots C | title = Mean differences in maternal body mass index and recurrent pregnancy loss: a systematic review and meta-analysis of observational studies | journal = Fertility and Sterility | volume = 116 | issue = 5 | pages = 1341–1348 | date = November 2021 | pmid = 34412893 | pmc = 8608000 | doi = 10.1016/j.fertnstert.2021.06.019 }}</ref> Despite this evidence, research studies aimed to establish a relationship between RPL and BMI, which incorporates height and weight, have produced inconsistent results. A systematic review found that women with a history of RPL had higher BMI's by an average difference of 0.9&nbsp;kg/m² than women without. These findings, however, were not statistically significant and not exclusive to BMI's within the overweight and obese range.<ref name="Eapen_2021" /> Another review and meta-analysis found that women with a BMI above 25 were more likely to have RPL and more likely to have a subsequent miscarriage, although the quality of evidence was low given that most of the studies were observational.<ref name="Ng_2021_2" /> It is important to consider that BMI can be influenced by numerous other conditions and modifiable risk factors (ie. poor nutrition, activity level, diabetes), therefore should not be regarded as a direct cause of RPL.<ref name="Eapen_2021" />
* '''Stress''': Research found that there is "increased relative risk of spontaneous abortion (odds ratio 1.28, 95% confidence interval 1.05-1.57)...for women experiencing high job stress."<ref name="Brandt_1992">{{cite journal | vauthors = Brandt LP, Nielsen CV | title = Job stress and adverse outcome of pregnancy: a causal link or recall bias? | journal = American Journal of Epidemiology | volume = 135 | issue = 3 | pages = 302–311 | date = February 1992 | pmid = 1546706 | doi = 10.1093/oxfordjournals.aje.a116284 }}</ref> Another research review found that the risk of miscarriage is higher for women with a "history of exposure to psychological stress (OR 1.42, 95% CI 1.19–1.70)"<ref name="Qu_2017">{{cite journal | vauthors = Qu F, Wu Y, Zhu YH, Barry J, Ding T, Baio G, Muscat R, Todd BK, Wang FF, Hardiman PJ | display-authors = 6 | title = The association between psychological stress and miscarriage: A systematic review and meta-analysis | journal = Scientific Reports | volume = 7 | issue = 1 | pages = 1731 | date = May 2017 | pmid = 28496110 | pmc = 5431920 | doi = 10.1038/s41598-017-01792-3 | bibcode = 2017NatSR...7.1731Q }}</ref>  However, the authors of these studies<ref name="Brandt_1992" /><ref name="Qu_2017" /> also point out that measuring stress is difficult, and that the results must therefore be interpreted with some caution. In addition, one of the studies<ref name="Qu_2017" /> notes that, while there are no randomized trials to study stress as it relates to pregnancy loss, one study found that a program of structured psychological support increased live birth rate among women with recurrent miscarriage.<ref>{{cite journal | vauthors = Liddell HS, Pattison NS, Zanderigo A | title = Recurrent miscarriage--outcome after supportive care in early pregnancy | journal = The Australian & New Zealand Journal of Obstetrics & Gynaecology | volume = 31 | issue = 4 | pages = 320–322 | date = November 1991 | pmid = 1799343 | doi = 10.1111/j.1479-828x.1991.tb02811.x | s2cid = 9800035 }}</ref>