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Retained Placenta
Introduction
‘I find it both amongst the ancients and moderns there have been different opinions and directions about delivering the placenta; some alleging that it should be delivered slowly, or left to come, of itself; others, that the hand should be immediately introduced into the uterus, to separate and bring it away … So in my opinion we ought to go the middle way, never to assist but when we find it necessary: on the one hand, not to torture nature when it is self-sufficient, nor delay too long, because it is possible that the placenta should be sometimes, though seldom, retained several days’. William SmellieTreatise on the Theory and Practice of Midwifery. London: D Wilson; 1752:239.
The delivery of the placenta is the most dangerous point of pregnancy for the woman. Before delivery there is blood flow to the placental bed of around 500 mL per minute, and if the uterus does not contract as the placenta detaches, this flow will continue and the mother can exsanguinate within minutes. Great care is therefore taken to ensure that the placenta delivers cleanly and the uterus contracts immediately afterwards. The routine care is briefly described below, followed by the management of delayed placental separation. More details can be found in Chapter 34 .
Routine Management of the Third Stage
It is now recognized that it is the oxytocic drug that prevents excessive blood loss − the other components of the ‘active management package’ appear to have little or no benefit.
Oxytocic Drugs
Oxytocin 5-10 units is now accepted to be the first-line oxytocic for routine management and is given immediately after delivery of the fetus. Oxytocin is more effective when given intravenously than when given intramuscularly, but must be given over at least 1 minute as rapid administration drops the blood pressure by 20 mmHg. Carbetocin is of equivalent efficacy to IM oxytocin and is heat stable, but more expensive. The oxytocin/ergometrine combination (Syntometrine) is slightly more effective than IM oxytocin, but the ergometrine causes vomiting and hypertension. Oral misoprostol has side effects of shivering and raised temperature and is less effective, but is an alternative for use where oxytocin is unavailable.
Therefore, the optimal choice for women at high risk appears to be either Syntometrine or IV oxytocin, although both are associated with potentially dangerous side effects. IM oxytocin or carbetocin are weaker appear to be slightly less effective, but also have less side effects and so may be a better option for routine use in low risk women.
Cord Clamping
The timing of cord clamping has been the topic of debate for over 200 years. There appears to be no maternal benefit of early cord clamping and it prevents around 90 mL of blood transferring to the baby from the placenta. In premature births, early cord clamping increases neonatal mortality whilst in term birth it increases rates of iron deficiency anaemia with consequent effects on motor and social development. Most authorities therefore recommend that the cord is not clamped until 2–3 minutes after birth. For those babies who need immediate neonatal care this can either be received at the bedside (using a small resuscitation trolley if needed), or ‘cord milking’ can be employed. This involves slowly squeezing the cord between finger and thumb and sliding the fingers along the cord for about 20 cm towards the fetus two or three times before clamping the cord. There are concerns that this technique could cause fetal cardiac overload and it is therefore not currently recommended.
‘Another thing very injurious to the child, is the tying and cutting of the navel string too soon which should always be left not only until the child has repeatedly breathed, but till all pulsations in the cord cease. As otherwise the child is much weaker than it ought to be, a portion of the blood being left in the placenta, which ought to have been in the child.’ Erasmus Darwin (British physician, philosopher and grandfather of Charles Darwin)Zoonomia; 1794, Part I. London: J. Johnson.
Controlled Cord Traction
Controlled cord traction is performed at the time of the first contraction following delivery of the baby when signs of separation are seen. Traction before this can increase blood loss and cause uterine inversion ( Chapter 40 ). The birth attendant stabilizes the uterus, and pushes the uterine body upwards with one hand while the other hand applies continuous traction on the umbilical cord to extract the placenta. A large WHO randomized trial has shown that this procedure has minimal effect on blood loss but shortens the length of the third stage slightly.
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