Placenta praevia

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Placenta praevia
Synonyms Placenta previa
Placta prv.jpg
Diagram showing a placenta previa (Grade IV )
Specialty Obstetrics
Symptoms Bright red vaginal bleeding without pain[1]
Complications Mother: Bleeding after delivery[2]
Baby: Fetal growth restriction[1]
Usual onset Second half of pregnancy[1]
Risk factors Older age, smoking, prior cesarean section, labor induction, or termination of pregnancy[3][4]
Diagnostic method Ultrasound[1]
Similar conditions Placental abruption[1]
Treatment Bed rest, cesarean section[1]
Frequency 0.5% of pregnancies[5]

Placenta praevia is when the placenta attaches inside the uterus but near or over the cervical opening.[1] Symptoms include vaginal bleeding in the second half of pregnancy.[1] The bleeding is bright red and tends not to be associated with pain.[1] Complications may include placenta accreta, dangerously low blood pressure, or bleeding after delivery.[2][4] Complications for the baby may include fetal growth restriction.[1]

Risk factors include pregnancy at an older age and smoking as well as prior cesarean section, labor induction, or termination of pregnancy.[3][4] Diagnosis is by ultrasound.[1] It is classified as a complication of pregnancy.[1]

For those who are less than 36 weeks pregnant with only a small amount of bleeding recommendations may include bed rest and avoiding sexual intercourse.[1] For those after 36 weeks of pregnancy or with a significant amount of bleeding, cesarean section is generally recommended.[1] In those less than 36 weeks pregnant, corticosteroids may be given to speed development of the babies lungs.[1] Cases that occur in early pregnancy may resolve on their own.[1]

It affects approximately 0.5% of pregnancies.[5] After four cesarean section it, however, effects 10% of pregnancies.[4] Rates of disease have increased over the late 20th century and early 21st century.[3] The condition was first described in 1685 by Paul Portal.[6]

Video explanation

Signs and symptoms[edit]

Women with placenta previa often present with painless, bright red vaginal bleeding. This commonly occurs around 32 weeks of gestation, but can be as early as late mid-trimester.[7] 51.6% of women with placenta previa have antepartum haemorrhage.[8] This bleeding often starts mildly and may increase as the area of placental separation increases. Previa should be suspected if there is bleeding after 24 weeks of gestation. Bleeding after delivery occurs in about 22% of those affected.[2]

Women may also present as a case of failure of engagement of fetal head.[9]

Cause[edit]

Exact cause of placenta previa is unknown. It is hypothesized to be related to abnormal vascularisation of the endometrium caused by scarring or atrophy from previous trauma, surgery, or infection. These factors may reduce differential growth of lower segment, resulting in less upward shift in placental position as pregnancy advances.[10]

Risk factors[edit]

Risk factors with their odds ratio[11]
Risk factor Odds ratio
Maternal age ≥ 40 (vs. < 20) 9.1
Illicit drugs 2.8
≥ 1 previous Cesarean section 2.7
Parity ≥ 5 (vs. para 0) 2.3
Parity 2–4 (vs. para 0) 1.9
Prior abortion 1.9
Smoking 1.6
Congenital anomalies 1.7
Male fetus (vs. female) 1.1
Pregnancy-induced hypertension 0.4

The following have been identified as risk factors for placenta previa:

  • Previous placenta previa (recurrence rate 4–8%),[12] caesarean delivery,[13] myomectomy[9] or endometrium damage caused by D&C.[12]
  • Women who are younger than 20 are at higher risk and women older than 35 are at increasing risk as they get older.
  • Alcohol use during pregnancy was previous listed as a risk factor, but is discredited by this article.[14]
  • Women who have had previous pregnancies ( multiparity ), especially a large number of closely spaced pregnancies, are at higher risk due to uterine damage.[9]
  • Smoking during pregnancy;[15] cocaine use during pregnancy[16][17]
  • Women with a large placentae from twins or erythroblastosis are at higher risk.
  • Race is a controversial risk factor, with some studies finding that people from Asia and Africa are at higher risk and others finding no difference.
  • Placental pathology (Vellamentous insertion, succinturiate lobes, bipartite i.e. bilobed placenta etc.)[12]
  • Baby is in an unusual position: breech (buttocks first) or transverse (lying horizontally across the womb).

Placenta previa is itself a risk factor of placenta accreta.

Classification[edit]

Traditionally, four grades of placenta previa were used,[15] however now it is more common to simply differentiate between 'major' and 'minor' cases.[18]

Type Description
Minor Placenta is in lower uterine segment, but the lower edge does not cover the internal os
Major Placenta is in lower uterine segment, and the lower edge covers the internal os

Other than that placenta previa can be also classified as :

Complete : When the placenta completely covers the cervix.

Partial : When the placenta partially covers the cervix.

Marginal : When the placenta ends near the edge of the cervix, about 2 cm from the internal cervical os.

Diagnosis[edit]

History may reveal antepartum hemorrhage. Abdominal examination usually finds the uterus non-tender, soft and relaxed. Leopold's Maneuvers may find the fetus in an oblique or breech position or lying transverse as a result of the abnormal position of the placenta. Malpresentation is found in about 35% cases.[19] Vaginal examination is avoided in known cases of placenta previa.[15]

Confirmatory[edit]

Previa can be confirmed with an ultrasound.[20] Transvaginal ultrasound has superior accuracy as compared to transabdominal one, thus allowing measurement of distance between placenta and cervical os. This has rendered traditional classification of placenta previa obsolete.[21][22][23][24]

False positives may be due to following reasons:[25]

  • Overfilled bladder compressing lower uterine segment
  • Myometrial contraction simulating placental tissue in abnormally low location
  • Early pregnancy low position, which in third trimester may be entirely normal due to differential growth of the uterus.

In such cases, repeat scanning is done after an interval of 15–30 minutes.

In parts of the world where ultrasound is unavailable, it is not uncommon to confirm the diagnosis with an examination in the surgical theatre. The proper timing of an examination in theatre is important. If the woman is not bleeding severely she can be managed non-operatively until the 36th week. By this time the baby's chance of survival is as good as at full term.

Management[edit]

An initial assessment to determine the status of the mother and fetus is required. Although mothers used to be treated in the hospital from the first bleeding episode until birth, it is now considered safe to treat placenta previa on an outpatient basis if the fetus is at less than 30 weeks of gestation, and neither the mother nor the fetus are in distress. Immediate delivery of the fetus may be indicated if the fetus is mature or if the fetus or mother are in distress. Blood volume replacement (to maintain blood pressure) and blood plasma replacement (to maintain fibrinogen levels) may be necessary.

Corticosteroids are indicated at 24–34 weeks gestation, given the higher risk of premature birth.[1]

Delivery[edit]

The method of delivery is determined by clinical state of the mother, fetus and ultrasound findings. In minor degrees (traditional grade I and II), vaginal delivery is possible. RCOG recommends that the placenta should be at least 2 cm away from internal os for an attempted vaginal delivery.[26] When a vaginal delivery is attempted, consultant obstetrician and anesthetists are present in delivery suite. In cases of fetal distress and major degrees (traditional grade III and IV) a caesarean section is indicated. Caesarian section is contraindicated in cases of disseminated intravascular coagulation. An obstetrician may need to divide the anterior lying placenta. In such cases, blood loss is expected to be high and thus blood and blood products are always kept ready. In rare cases, hysterectomy may be required.[27]

Complications[edit]

Maternal[edit]

  • Antepartum hemorrhage
  • Malpresentation
  • Abnormal placentation
  • Postpartum hemorrhage
  • Placenta previa increases the risk of puerperal sepsis and postpartum hemorrhage because the lower segment to which the placenta was attached contracts less well post-delivery.

Fetal[edit]

  • IUGR (15% incidence)[12]
  • Hypoxia
  • Premature delivery
  • Death

Epidemiology[edit]

Placenta previa occurs approximately one of every 200 births.[5] It has been suggested that incidence of placenta previa is increasing due to increased rate of Caesarian section.[28]

Perinatal mortality rate of placenta previa is 3-4 times higher than normal pregnancies.[29]

History[edit]

In places where a Caesarean section could not be performed due to the lack of a surgeon or equipment, infant could be delivered vaginally. There were two ways of doing this with a placenta previa:

  • The baby's head can be brought down to the placental site (if necessary with Willet's forceps or a vulsellum) and a weight attached to its scalp
  • A leg can be brought down and the baby's buttocks used to compress the placental site

References[edit]

  1. ^ a b c d e f g h i j k l m n o p q "Placenta Previa - Gynecology and Obstetrics - Merck Manuals Professional Edition". Merck Manuals Professional Edition. October 2017. Retrieved 9 December 2017. 
  2. ^ a b c Fan, D; Xia, Q; Liu, L; Wu, S; Tian, G; Wang, W; Wu, S; Guo, X; Liu, Z (2017). "The Incidence of Postpartum Hemorrhage in Pregnant Women with Placenta Previa: A Systematic Review and Meta-Analysis". PloS one. 12 (1): e0170194. doi:10.1371/journal.pone.0170194. PMID 28107460. 
  3. ^ a b c Palacios-Jaraquemada, JM (April 2013). "Caesarean section in cases of placenta praevia and accreta". Best practice & research. Clinical obstetrics & gynaecology. 27 (2): 221–32. doi:10.1016/j.bpobgyn.2012.10.003. PMID 23127895. 
  4. ^ a b c d Allahdin, S; Voigt, S; Htwe, TT (2011). "Management of placenta praevia and accreta". Journal of obstetrics and gynaecology : the journal of the Institute of Obstetrics and Gynaecology. 31 (1): 1–6. doi:10.3109/01443615.2010.532248. PMID 21280984. 
  5. ^ a b c Cresswell, JA; Ronsmans, C; Calvert, C; Filippi, V (June 2013). "Prevalence of placenta praevia by world region: a systematic review and meta-analysis". Tropical medicine & international health : TM & IH. 18 (6): 712–24. doi:10.1111/tmi.12100. PMID 23551357. 
  6. ^ Baskett, Thomas F.; Calder, Andrew A.; Arulkumaran, Sabaratnam (2014). Munro Kerr's Operative Obstetrics E-Book. Elsevier Health Sciences. p. 178. ISBN 9780702052484. 
  7. ^ Callander, Kevin P. Hanretty ; illustrated by Ian Ramsden, Robin (2004). Obstetrics illustrated (6th ed., Reprinted. ed.). Edinburgh [etc.]: Churchill Livingstone. p. 187. ISBN 0443072671. 
  8. ^ Fan, Dazhi; Wu, Song; Liu, Li; Xia, Qing; Wang, Wen; Guo, Xiaoling; Liu, Zhengping (9 January 2017). "Prevalence of antepartum hemorrhage in women with placenta previa: a systematic review and meta-analysis". Scientific Reports. 7: 40320. doi:10.1038/srep40320. 
  9. ^ a b c Brinsden, Judith Collier, Murray Longmore, Mark (2006). Oxford handbook of clinical specialties (7th ed.). Oxford: Oxford University Press. p. 1970. ISBN 9780198530855. 
  10. ^ Dashe, JS; McIntire, DD; Ramus, RM; Santos-Ramos, R; Twickler, DM (May 2002). "Persistence of placenta previa according to gestational age at ultrasound detection". Obstetrics and gynecology. 99 (5 Pt 1): 692–7. doi:10.1016/s0029-7844(02)01935-x. PMID 11978274. 
  11. ^ Jr, [edited by] E. Albert Reece, John C. Hobbins ; foreword by Norm F. Gant, (2006). Clinical obstetrics : the fetus and mother (3 ed.). Malden, MA: Blackwell Pub. p. 1050. ISBN 978-1-4051-3216-9. 
  12. ^ a b c d Kendrick, Chantal Simon, Hazel Everitt, Tony (2005). Oxford handbook of general practice (2nd ed.). Oxford: Oxford University Press. p. 793. ISBN 9780198565819. 
  13. ^ Weerasekera, D. S. (2000). "Placenta previa and scarred uterus — an obstetrician's dilemma". Journal of Obstetrics & Gynaecology. 20 (5): 484–5. doi:10.1080/014436100434659. PMID 15512632. 
  14. ^ Aliyu, MH; Lynch, O; Nana, PN; Alio, AP; Wilson, RE; Marty, PJ; Zoorob, R; Salihu, HM (July 2011). "Alcohol consumption during pregnancy and risk of placental abruption and placenta previa". Maternal and child health journal. 15 (5): 670–6. doi:10.1007/s10995-010-0615-6. PMID 20437196. 
  15. ^ a b c Arulkumaran, edited by Richard Warren, Sabaratnam (2009). Best practice in labour and delivery (1st ed., 3rd printing. ed.). Cambridge: Cambridge University Press. pp. 142–146. ISBN 978-0-521-72068-7. 
  16. ^ Handler, A; Kistin, N; Davis, F; Ferré, C (Apr 15, 1991). "Cocaine use during pregnancy: perinatal outcomes". American Journal of Epidemiology. 133 (8): 818–25. PMID 2021149. 
  17. ^ Kistin, N; Handler, A; Davis, F; Ferre, C (July 1996). "Cocaine and cigarettes: a comparison of risks". Paediatric and Perinatal Epidemiology. 10 (3): 269–78. doi:10.1111/j.1365-3016.1996.tb00050.x. PMID 8822770. 
  18. ^ https://www.rcog.org.uk/en/guidelines-research-services/guidelines/gtg27/
  19. ^ Cotton, DB; Read, JA; Paul, RH; Quilligan, EJ (Jul 15, 1980). "The conservative aggressive management of placenta previa". American Journal of Obstetrics and Gynecology. 137 (6): 687–95. doi:10.1016/s0002-9378(15)33242-7. PMID 7395932. 
  20. ^ Bhide, Amar; Thilaganathan, Basky (2004). "Recent advances in the management of placenta previa". Current Opinion in Obstetrics and Gynecology. 16 (6): 447–51. doi:10.1097/00001703-200412000-00002. PMID 15534438. 
  21. ^ Oppenheimer, LW; Farine, D; Ritchie, JW; Lewinsky, RM; Telford, J; Fairbanks, LA (October 1991). "What is a low-lying placenta?". American Journal of Obstetrics and Gynecology. 165 (4 Pt 1): 1036–8. doi:10.1016/0002-9378(91)90465-4. PMID 1951509. 
  22. ^ Neale, E. J.; Rogers, M. S. (1 July 1989). "Vaginal ultrasound for ruling out placenta previa. Case report". BJOG: an International Journal of Obstetrics and Gynaecology. 96 (7): 881–881. doi:10.1111/j.1471-0528.1989.tb03334.x. 
  23. ^ Smith, RS; Lauria, MR; Comstock, CH; Treadwell, MC; Kirk, JS; Lee, W; Bottoms, SF (January 1997). "Transvaginal ultrasonography for all placentas that appear to be low-lying or over the internal cervical os". Ultrasound in Obstetrics & Gynecology. 9 (1): 22–4. doi:10.1046/j.1469-0705.1997.09010022.x. PMID 9060125. 
  24. ^ Farine, D; Fox, HE; Jakobson, S; Timor-Tritsch, IE (September 1988). "Vaginal ultrasound for diagnosis of placenta previa". American Journal of Obstetrics and Gynecology. 159 (3): 566–9. doi:10.1016/s0002-9378(88)80009-7. PMID 3048096. 
  25. ^ Sutton, David (2003). Textbook of radiology and imaging (7th ed.). Edinburgh: Churchill Livingstone. p. 1064. ISBN 0443071098. 
  26. ^ "Placenta Previa, Placenta Previa Accreta and Vasa Previa: Diagnosis and Management". RCOG Guidelines — Green-top 27. Retrieved 15 January 2013. 
  27. ^ Kayem, G; Davy, C; Goffinet, F; Thomas, C; Clément, D; Cabrol, D (September 2004). "Conservative versus extirpative management in cases of placenta accreta". Obstetrics and gynecology. 104 (3): 531–6. doi:10.1097/01.AOG.0000136086.78099.0f. PMID 15339764. 
  28. ^ Miller, DA; Chollet, JA; Goodwin, TM (July 1997). "Clinical risk factors for placenta previa-placenta accreta". American Journal of Obstetrics and Gynecology. 177 (1): 210–4. doi:10.1016/s0002-9378(97)70463-0. PMID 9240608. 
  29. ^ Crane, JM; van den Hof, MC; Dodds, L; Armson, BA; Liston, R (April 1999). "Neonatal outcomes with placenta previa". Obstetrics and gynecology. 93 (4): 541–4. doi:10.1016/s0029-7844(98)00480-3. PMID 10214830. 

External links[edit]

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