The main symptom of miscarriage is vaginal bleeding, and up to 30% of all pregnancies may end in miscarriage.[6]Makrydimas G, Sebire NJ, Lolis D, et al. Fetal loss following ultrasound diagnosis of a live fetus at 6-10 weeks of gestation. Ultrasound Obstet Gynecol. 2003 Oct;22(4):368-72.
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[7]Ellish NJ, Saboda K, O'Connor J, et al. A prospective study of early pregnancy loss. Hum Reprod. 1996 Feb;11(2):406-12.
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[8]Regan L, Rai R. Epidemiology and the medical causes of miscarriage. Baillieres Best Pract Res Clin Obstet Gynaecol. 2000 Oct;14(5):839-54.
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[9]Moore J, Shillito TJ, Walker JJ. Current issues in management of miscarriage and early pregnancy bleeding. Hosp Med. 2002 Mar;63(3):134-5.
http://www.ncbi.nlm.nih.gov/pubmed/11933813?tool=bestpractice.com
[10]Farr SL, Schieve LA, Jamieson DJ. Pregnancy loss among pregnancies conceived through assisted reproductive technology, United States, 1999-2002. Am J Epidemiol. 2007 Jun 15;165(12):1380-8.
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[11]Wilcox AJ, Weinberg CR, O'Connor JF, et al. Incidence of early loss of pregnancy. N Engl J Med. 1988 Jul 28;319(4):189-94.
http://www.ncbi.nlm.nih.gov/pubmed/3393170?tool=bestpractice.com
The majority of miscarriages (around 80%) occur in the first trimester.[11]Wilcox AJ, Weinberg CR, O'Connor JF, et al. Incidence of early loss of pregnancy. N Engl J Med. 1988 Jul 28;319(4):189-94.
http://www.ncbi.nlm.nih.gov/pubmed/3393170?tool=bestpractice.com
[12]Wang X, Chen C, Wang L, et al. Conception, early pregnancy loss, and time to clinical pregnancy: a population-based prospective study. Fertil Steril. 2003 Mar;79(3):577-84.
https://www.doi.org/10.1016/s0015-0282(02)04694-0
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Approximately 1% to 2% of all second trimester pregnancies miscarry before 24 weeks.[13]Wyatt PR, Owolabi T, Meier C, et al. Age-specific risk of fetal loss observed in a second trimester serum screening population. Am J Obstet Gynecol. 2005 Jan;192(1):240-6.
https://www.doi.org/10.1016/j.ajog.2004.06.099
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In 2008, there were an estimated 6,578,000 pregnancies in the US, which resulted in 1,118,000 spontaneous fetal losses.[14]Ventura SJ, Abma JC, Mosher WD, et al. Estimated pregnancy rates for the United States, 1990-2000: an update. Natl Vital Stat Rep. 2004 Jun 15;52(23):1-9.
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There is no reason to suspect that overall spontaneous miscarriage rates are markedly different in other parts of the world, and one prospective longitudinal population-based study in Sweden reported clinical miscarriage in 12% of reported pregnancies.[15]Blohm F, Friden B, Milsom I. A prospective longitudinal population-based study of clinical miscarriage in an urban Swedish population. BJOG. 2008 Jan;115(2):176-82;discussion 183.
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However, the rate of spontaneous loss of unrecognised pregnancies after implantation has been estimated at up to 31%.[11]Wilcox AJ, Weinberg CR, O'Connor JF, et al. Incidence of early loss of pregnancy. N Engl J Med. 1988 Jul 28;319(4):189-94.
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Recurrent miscarriages affect approximately 1% of couples trying to conceive.[16]Stirrat GM. Recurrent miscarriage. Lancet. 1990 Sep 15;336(8716):673-5.
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