O principal sintoma de aborto espontâneo, sendo que até 30% de todas as gestações podem sofrer aborto espontâneo.[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.
https://obgyn.onlinelibrary.wiley.com/doi/full/10.1002/uog.204
http://www.ncbi.nlm.nih.gov/pubmed/14528471?tool=bestpractice.com
[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.
http://www.ncbi.nlm.nih.gov/pubmed/8671233?tool=bestpractice.com
[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.
http://www.ncbi.nlm.nih.gov/pubmed/11023804?tool=bestpractice.com
[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.
http://www.ncbi.nlm.nih.gov/pubmed/17351291?tool=bestpractice.com
[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
A maioria dos abortos espontâneos (aproximadamente 80%) ocorre no primeiro trimestre.[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
http://www.ncbi.nlm.nih.gov/pubmed/12620443?tool=bestpractice.com
Aproximadamente 1% a 2% de todas as gestações no segundo trimestre resultam em aborto espontâneo antes de 24 semanas.[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
http://www.ncbi.nlm.nih.gov/pubmed/15672031?tool=bestpractice.com
Em 2008, havia uma estimativa de 6,578,000 gestações nos EUA, o que resultou em 1,118,000 perdas fetais espontâneas.[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.
http://www.ncbi.nlm.nih.gov/pubmed/15224964?tool=bestpractice.com
Não há motivos para suspeitar que os índices gerais de abortos espontâneos sejam marcantemente diferentes em outras partes do mundo, e um estudo prospectivo de base populacional, realizado na Suécia, relatou aborto espontâneo clínico em 12% das gestações relatadas.[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.
https://obgyn.onlinelibrary.wiley.com/doi/full/10.1111/j.1471-0528.2007.01426.x
http://www.ncbi.nlm.nih.gov/pubmed/18081599?tool=bestpractice.com
Entretanto, o índice de perdas fetais espontâneas de gestações não reconhecidas após a implantação foi estimado em até 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.
http://www.ncbi.nlm.nih.gov/pubmed/3393170?tool=bestpractice.com
O abortamento recorrente afeta aproximadamente 1% dos casais que tentam conceber.[16]Stirrat GM. Recurrent miscarriage. Lancet. 1990 Sep 15;336(8716):673-5.
https://www.doi.org/10.1016/0140-6736(90)92159-f
http://www.ncbi.nlm.nih.gov/pubmed/1975862?tool=bestpractice.com