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The retained placenta—new insights into an old problem
European Journal of Obstetrics & Gynecology and Reproductive Biology 102 (2002) 109–110
Editorial
The retained placenta—new insights into an old problem Retained placentas affect 0.5–3% of women following delivery. Until recently, all have required manual removal under anaesthesia. In the developed world, this is usually little more than an inconvenience. In the developing world, however, this complication is often fatal. The combined risks of severe antepartum anaemia, a rural home delivery, poor transportation and shortages in health facilities, mean that the mortality from this condition is between 3 and 6% in rural areas [1]. A simple, cheap, low technology solution is urgently needed and recent developments in the understanding of the pathophysiology of retained placentas may provide it. Dynamic visualisation of the uterus during the third stage of labour using ultrasound has revolutionised our understanding of the retained placenta. The normal third stage of labour can be divided into three distinct phases. The latent phase is when the whole uterus can be seen to contract except for the area behind the placenta. This phase is followed by the contraction phase (when the retro-placental myometrium contracts), the detachment and the expulsion phases [2]. The length of the third stage is dependent on the length of the latent phase, and failure of retro-placental contraction is seen to be the cause of retained placentas. These findings raise two questions. Why is that area of myometrium not contracting, and is there a way in which it can be made to contract and thus expel the placenta? Whatever is causing the post-partum retro-placental contractile failure is likely to have been present throughout labour. If so, then the lack of contraction in this area might have many benefits to the fetus. It could act as a protective mechanism to prevent intrapartum abruptio, and might also be protective against fetal anoxia by ensuring an uninterrupted maternal blood supply to the placental bed during contractions. On the negative side, however, a large area of non-contractile myometrium during labour could lead to poor intrauterine pressures and dysfunctional labours. Studies are underway to investigate the pathophysiology underlying the retro-placental contractile failure. It is clear that the placenta plays a crucial role in determining the time of labour onset, acting primarily as an inhibitor of myometrial contractility. Progesterone and nitric oxide are major inhibitors produced by the placenta and it may be that the persistence of one, or both of these might be responsible for the retro-placental contractile failure in retained placentas. The association of retained placentas with both induction of labour and prematurity suggests that in some cases the exogenous pro-contractile forces overcome the placental
inhibition enough to cause labour, but not enough to cause placental expulsion. The second importance of the retro-placental contractile failure in retained placenta is its implication for treatment. The direct delivery of an oxytocic to the retro-placental myometrium through the umbilical vein was first tried in the 1960s. Now, following the publication of a Cochrane review [3] it is being recommended as first line treatment for retained placentas by the World Health Organisation [4]. This recommendation comes despite some confusion about the optimal dosage and technique for the oxytocin injection. Randomised trials so far have used doses ranging from 10 to 100 units and the Cochrane analysis includes them all in the same meta-analysis. There are as yet no comparative studies to determine the optimal dosage, but when the trials are sorted and re-analysed according to dosage, meta-analysis suggests that the technique is more effective when doses of over 20 units are used [1]. In addition to inadequate doses, there may also have been a problem in previous trials with the delivery of the oxytocin to the myometrium. In all randomised trials so far, the method used has been to simply inject diluted oxytocin into the umbilical cord. However, Pipingas, using injections of radio-opaque dye into delivered placentas, demonstrated that solutions injected using this technique rarely reached the placental bed [5]. He went on to show that the most effective technique is to inject 30 ml of solution down a infant naso-gastic tube which has been threaded down the umbilical vein. A recent observational study found a 92% success rate in delivering retained placentas when high doses of oxytocin were injected using the Pipingas method [6]. If this study is confirmed by ongoing randomised trials then it could have a major impact on the management of the retained placenta. For women in privileged situations, it will save them an anaesthetic and some discomfort. For anaemic women in rural Africa who have travelled 100 miles to reach a hospital only to find it has no working theatre, it could save their lives. References [1] Weeks AD. The Retained Placenta. Afr Health Sci 2001;1:36–41. [2] Herman A., Weinraub Z., Bukovsky I. et al. Dynamic ultrasonographic imaging of the third stage of labor: new perspectives into third stage mechanism Am. J. Obstet. Gynecol. 168 1993 1496–1499 [3] Carroli G, Bergel E. Umbilical vein injection for management of retained placenta (Cochrane Review). In: The Cochrane Library, Issue 4. Oxford: Update Software, 2000.
0301-2115/02/$ – see front matter # 2002 Elsevier Science Ireland Ltd. All rights reserved. PII: S 0 3 0 1 - 2 1 1 5 ( 0 1 ) 0 0 5 9 2 - 9
110
Editorial
[4] Purwar MB. Practical recommendations for umbilical vein injection for management of retained placenta. In: Gu¨ lmezoglu AM, Villar J, editors. The WHO Reproductive Health Library, vol. 4. Geneva: World Health Organization, 2001. [5] Pipingas A, Hofmeyr GJ, Sesel KR. Umbilical vessel oxytocin administration for retained placenta: in vitro study of various infusion techniques. Am J Obstet Gynecol 1993;168:793–5. [6] Chauhan P. Volume and site of injection of oxytocin solution is important in the medical treatment of retained placenta. Int J Obstet Gynecol 2000;70:83.
Andrew D. Weeks* Florence M. Mirembe Department of Obstetrics and Gynaecology Faculty of Medicine, Makerere University Kampala, Uganda * Tel.: þ256-77-615-410; fax: þ256-41-533-451 E-mail address: [email protected] (A.D. Weeks) Received 23 October 2001; accepted 9 November 2001
Editorial
The retained placenta—new insights into an old problem Retained placentas affect 0.5–3% of women following delivery. Until recently, all have required manual removal under anaesthesia. In the developed world, this is usually little more than an inconvenience. In the developing world, however, this complication is often fatal. The combined risks of severe antepartum anaemia, a rural home delivery, poor transportation and shortages in health facilities, mean that the mortality from this condition is between 3 and 6% in rural areas [1]. A simple, cheap, low technology solution is urgently needed and recent developments in the understanding of the pathophysiology of retained placentas may provide it. Dynamic visualisation of the uterus during the third stage of labour using ultrasound has revolutionised our understanding of the retained placenta. The normal third stage of labour can be divided into three distinct phases. The latent phase is when the whole uterus can be seen to contract except for the area behind the placenta. This phase is followed by the contraction phase (when the retro-placental myometrium contracts), the detachment and the expulsion phases [2]. The length of the third stage is dependent on the length of the latent phase, and failure of retro-placental contraction is seen to be the cause of retained placentas. These findings raise two questions. Why is that area of myometrium not contracting, and is there a way in which it can be made to contract and thus expel the placenta? Whatever is causing the post-partum retro-placental contractile failure is likely to have been present throughout labour. If so, then the lack of contraction in this area might have many benefits to the fetus. It could act as a protective mechanism to prevent intrapartum abruptio, and might also be protective against fetal anoxia by ensuring an uninterrupted maternal blood supply to the placental bed during contractions. On the negative side, however, a large area of non-contractile myometrium during labour could lead to poor intrauterine pressures and dysfunctional labours. Studies are underway to investigate the pathophysiology underlying the retro-placental contractile failure. It is clear that the placenta plays a crucial role in determining the time of labour onset, acting primarily as an inhibitor of myometrial contractility. Progesterone and nitric oxide are major inhibitors produced by the placenta and it may be that the persistence of one, or both of these might be responsible for the retro-placental contractile failure in retained placentas. The association of retained placentas with both induction of labour and prematurity suggests that in some cases the exogenous pro-contractile forces overcome the placental
inhibition enough to cause labour, but not enough to cause placental expulsion. The second importance of the retro-placental contractile failure in retained placenta is its implication for treatment. The direct delivery of an oxytocic to the retro-placental myometrium through the umbilical vein was first tried in the 1960s. Now, following the publication of a Cochrane review [3] it is being recommended as first line treatment for retained placentas by the World Health Organisation [4]. This recommendation comes despite some confusion about the optimal dosage and technique for the oxytocin injection. Randomised trials so far have used doses ranging from 10 to 100 units and the Cochrane analysis includes them all in the same meta-analysis. There are as yet no comparative studies to determine the optimal dosage, but when the trials are sorted and re-analysed according to dosage, meta-analysis suggests that the technique is more effective when doses of over 20 units are used [1]. In addition to inadequate doses, there may also have been a problem in previous trials with the delivery of the oxytocin to the myometrium. In all randomised trials so far, the method used has been to simply inject diluted oxytocin into the umbilical cord. However, Pipingas, using injections of radio-opaque dye into delivered placentas, demonstrated that solutions injected using this technique rarely reached the placental bed [5]. He went on to show that the most effective technique is to inject 30 ml of solution down a infant naso-gastic tube which has been threaded down the umbilical vein. A recent observational study found a 92% success rate in delivering retained placentas when high doses of oxytocin were injected using the Pipingas method [6]. If this study is confirmed by ongoing randomised trials then it could have a major impact on the management of the retained placenta. For women in privileged situations, it will save them an anaesthetic and some discomfort. For anaemic women in rural Africa who have travelled 100 miles to reach a hospital only to find it has no working theatre, it could save their lives. References [1] Weeks AD. The Retained Placenta. Afr Health Sci 2001;1:36–41. [2] Herman A., Weinraub Z., Bukovsky I. et al. Dynamic ultrasonographic imaging of the third stage of labor: new perspectives into third stage mechanism Am. J. Obstet. Gynecol. 168 1993 1496–1499 [3] Carroli G, Bergel E. Umbilical vein injection for management of retained placenta (Cochrane Review). In: The Cochrane Library, Issue 4. Oxford: Update Software, 2000.
0301-2115/02/$ – see front matter # 2002 Elsevier Science Ireland Ltd. All rights reserved. PII: S 0 3 0 1 - 2 1 1 5 ( 0 1 ) 0 0 5 9 2 - 9
110
Editorial
[4] Purwar MB. Practical recommendations for umbilical vein injection for management of retained placenta. In: Gu¨ lmezoglu AM, Villar J, editors. The WHO Reproductive Health Library, vol. 4. Geneva: World Health Organization, 2001. [5] Pipingas A, Hofmeyr GJ, Sesel KR. Umbilical vessel oxytocin administration for retained placenta: in vitro study of various infusion techniques. Am J Obstet Gynecol 1993;168:793–5. [6] Chauhan P. Volume and site of injection of oxytocin solution is important in the medical treatment of retained placenta. Int J Obstet Gynecol 2000;70:83.
Andrew D. Weeks* Florence M. Mirembe Department of Obstetrics and Gynaecology Faculty of Medicine, Makerere University Kampala, Uganda * Tel.: þ256-77-615-410; fax: þ256-41-533-451 E-mail address: [email protected] (A.D. Weeks) Received 23 October 2001; accepted 9 November 2001