A PP observada no início da gestação pode migrar para uma posição normal à medida que a gestação evolui. Não se trata de uma verdadeira migração, mas de um crescimento diferencial que ocorre na extremidade superior da placenta em comparação com a extremidade inferior. Aproximadamente 85% das placentas prévias ocorridas entre a 15ª e a 20ª semana e aproximadamente um terço das placentas prévias ocorridas entre a 20ª e a 23ª semana não serão mais prévias no início do trabalho de parto.[36]Dashe JS, McIntire DD, Ramus RM, et al. Persistence of placenta previa according to gestational age at ultrasound detection. Obstet Gynecol. 2002 May;99(5 Pt 1):692-7.
http://www.ncbi.nlm.nih.gov/pubmed/11978274?tool=bestpractice.com
[49]Oppenheimer L, Holmes P, Simpson N, et al. Diagnosis of low-lying placenta: can migration in the third trimester predict outcome? Ultrasound Obstet Gynecol. 2001 Aug;18(2):100-2.
http://www.ncbi.nlm.nih.gov/pubmed/11529986?tool=bestpractice.com
[50]Predanic M, Perni SC, Baergen RN, et al. A sonographic assessment of different patterns of placenta previa "migration" in the third trimester of pregnancy. J Ultrasound Med. 2005 Jun;24(6):773-80.
http://www.ncbi.nlm.nih.gov/pubmed/15914681?tool=bestpractice.com
[51]Olive EC, Roberts CL, Nassar N, et al. Test characteristics of placental location screening by transabdominal ultrasound at 18-20 weeks. Ultrasound Obstet Gynecol. 2006 Dec;28(7):944-9.
http://www.ncbi.nlm.nih.gov/pubmed/17121427?tool=bestpractice.com
[76]Becker RH, Vonk R, Mende BC, et al. The relevance of placental location at 20-23 gestational weeks for prediction of placenta previa at delivery: evaluation of 8650 cases. Ultrasound Obstet Gynecol. 2001 Jun;17(6):496-501.
https://obgyn.onlinelibrary.wiley.com/doi/epdf/10.1046/j.1469-0705.2001.00423.x
http://www.ncbi.nlm.nih.gov/pubmed/11422970?tool=bestpractice.com
Prognóstico materno
O prognóstico materno geralmente é bom. As mulheres submetidas a partos cesáreos eletivos e de urgência têm risco de complicações associadas a esse procedimento.[77]Bergholt T, Stenderup JK, Vedsted-Jakobsen A, et al. Intraoperative surgical complication during cesarean section: an observational study of the incidence and risk factors. Acta Obstet Gynecol Scand. 2003 Mar;82(3):251-6.
https://obgyn.onlinelibrary.wiley.com/doi/full/10.1034/j.1600-0412.2003.00095.x
http://www.ncbi.nlm.nih.gov/pubmed/12694122?tool=bestpractice.com
Mulheres com PP apresentam aumento do risco de receberem transfusões de sangue (por sangramento pré-operatório, intraoperatório e pós-operatório), com os riscos associados (que variam de um local para outro).[78]Magan EF, Evans S, Hutchinson M, et al. Postpartum hemorrhage after cesarean delivery: an analysis of risk factors. South Med J. 2005 Jul;98(7):681-5.
http://www.ncbi.nlm.nih.gov/pubmed/16108235?tool=bestpractice.com
As mulheres apresentam aumento do risco de histerectomia puerperal, embora esse risco permaneça baixo (0.2%).[79]Watanasomsiri N, Rungruxsrivorn T, Chaithongwongwatthana S. Risk factors for cesarean hysterectomy in cesarean delivery. J Med Assoc Thai. 2006 Oct;89 Suppl 4:S100-4.
http://www.ncbi.nlm.nih.gov/pubmed/17725146?tool=bestpractice.com
[80]Daskalakis G, Anastasakis E, Papantoniou, et al. Emergency obstetric hysterectomy. Acta Obstet Gynecol Scand. 2007 Feb;86(2):223-7.
https://obgyn.onlinelibrary.wiley.com/doi/full/10.1080/00016340601088448
http://www.ncbi.nlm.nih.gov/pubmed/17364287?tool=bestpractice.com
Há um aumento do risco de PP em gestações subsequentes, embora esse risco permaneça baixo (<1%).[81]Yang Q, Wen SW, Oppenheimer L, et al. Association of caesarean delivery for first birth with placenta praevia and placental abruption in second pregnancy. BJOG. 2007 May;114(5):609-13.
http://www.ncbi.nlm.nih.gov/pubmed/17355267?tool=bestpractice.com
[82]Kennare, R, Tucker G, Heard A, et al. Risks of adverse outcomes in the next birth after a first cesarean delivery. Obstet Gynecol. 2007 Feb;109(2 Pt 1):270-6.
http://www.ncbi.nlm.nih.gov/pubmed/17267823?tool=bestpractice.com
Prognóstico fetal
O prognóstico fetal geralmente é bom, mas pode ficar comprometido por sangramento excessivo e por restrição do crescimento intrauterino.[83]Koifman A, Levy A, Zaulan Y, et al. The clinical significance of bleeding during the second trimester of pregnancy. Arch Gynecol Obstet. 2008 Jul;278(1):47-51.
http://www.ncbi.nlm.nih.gov/pubmed/18066562?tool=bestpractice.com
[84]Ananth CV, Demissie K, Smulian JC, et al. Relationship among placenta previa, fetal growth restriction, and preterm delivery: a population-based study. Obstet Gynecol. 2001 Aug;98(2):299-306.
http://www.ncbi.nlm.nih.gov/pubmed/11506849?tool=bestpractice.com
[85]Ananth CV, Smulian JC, Vintzileos AM. The effect of placenta previa on neonatal mortality: a population-based study in the United States, 1989 through 1997. Am J Obstet Gynecol. 2003 May;188(5):1299-304.
http://www.ncbi.nlm.nih.gov/pubmed/12748502?tool=bestpractice.com
Prognóstico neonatal
O prognóstico neonatal depende do grau de prematuridade, juntamente com a disponibilidade de cuidados pré-natais especializados.[85]Ananth CV, Smulian JC, Vintzileos AM. The effect of placenta previa on neonatal mortality: a population-based study in the United States, 1989 through 1997. Am J Obstet Gynecol. 2003 May;188(5):1299-304.
http://www.ncbi.nlm.nih.gov/pubmed/12748502?tool=bestpractice.com
[86]Salihu HM, Li QL, Rouse DJ, et al. Placenta previa: neonatal death after live births in the United States. Am J Obstet Gynecol. 2003 May;188(5):1305-9.
http://www.ncbi.nlm.nih.gov/pubmed/12748503?tool=bestpractice.com
[87]Lal AK, Hibbard JU. Placenta previa: an outcome-based cohort study in a contemporary obstetric population. Arch Gynecol Obstet. 2015 Aug;292(2):299-305.
http://www.ncbi.nlm.nih.gov/pubmed/25638449?tool=bestpractice.com
Ele também é afetado pelo grau de sangramento pré-parto, que pode causar anemia neonatal.[83]Koifman A, Levy A, Zaulan Y, et al. The clinical significance of bleeding during the second trimester of pregnancy. Arch Gynecol Obstet. 2008 Jul;278(1):47-51.
http://www.ncbi.nlm.nih.gov/pubmed/18066562?tool=bestpractice.com
[84]Ananth CV, Demissie K, Smulian JC, et al. Relationship among placenta previa, fetal growth restriction, and preterm delivery: a population-based study. Obstet Gynecol. 2001 Aug;98(2):299-306.
http://www.ncbi.nlm.nih.gov/pubmed/11506849?tool=bestpractice.com
Pode ocorrer um ligeiro aumento no risco de síndrome da morte súbita infantil.[88]Li DK, Wi S. Maternal placental abnormality and the risk of sudden infant death syndrome. Am J Epidemiol. 1999 Apr 1;149(7):608-11.
https://academic.oup.com/aje/article/149/7/608/167983
http://www.ncbi.nlm.nih.gov/pubmed/10192307?tool=bestpractice.com