‘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’.
Treatise on the Theory and Practice of Midwifery. London: D Wilson, 1752, p239
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.
Oxytocin 10 units intramuscularly is now accepted to be the first line oxytocic for routine management and is given immediately after delivery of the fetus. The oxytocin/ergometrine combination (Syntometrine ® ) is slightly more effective but causes vomiting and hypertension. Oral misoprostol is a less effective alternative for use where oxytocin is unavailable.
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. Most authorities therefore suggest 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 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. The birth attendant 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 recent trial has shown that this procedure has minimal effect on blood loss but shortens the length of the third stage slightly.
Uterine massage is added to the active management package by some authorities, even though there is little evidence for its benefit. After delivery of the placenta the fundus of the uterus is massaged every 15 minutes to ensure that the uterus is firmly contracted and not distending with clots.
With traditional or expectant management of the third stage of labour the placenta usually delivers within 10–20 minutes. With active management the placenta is commonly delivered within 5–10 minutes. In general, 90% of placentas deliver within 15 minutes, 96% within 30 minutes and 98% within 60 minutes. The incidence of retained placenta, therefore, depends on the time chosen. The rate is also higher in well resourced settings and has increased over time, although the reason for this is unclear.
Once time passes without placental delivery, the risk of haemorrhage increases and the chance of spontaneous delivery of the placenta decreases. The time at which one declares the placenta retained and takes active steps for its removal depends on the facilities and personnel available for safe anaesthesia, as well as the presence or absence of haemorrhage. These considerations are illustrated in Figure 21-1 .
Types of Retained Placenta
Trapped placenta : The placenta has separated from the uterine wall but is retained in the uterus. Clinically the uterus is small and contracted, but the fundus high. Ultrasound examination shows a well-contracted uterus with the placenta retained in a bulging lower segment.
Placenta adherens : ‘Adherence’ of the placenta is due to failure of the myometrium behind the placenta to contract. Until separation occurs, either partially or completely, these cases do not bleed excessively. Ultrasound shows the placenta within the uterine body attached to a thin, uncontracted myometrium.
Placenta accreta : This is usually detected at caesarean section, but can be found in small areas following vaginal delivery (see below). The management of placenta praevia accreta is discussed in Chapter 19 .
Retained placenta in previous pregnancy; the recurrence risk is 25%.
Poor myometrial contractility (causes placenta adherens): preterm labour (around 25% of all deliveries at 25 weeks have a retained placenta compared to only 3% at term), uterine fibroids, labour induction or need for oxytocin augmentation.
Disrupted myometrial−placental interface (causes partial accreta): pre-eclampsia, previous miscarriage and abortion, uterine anomaly (e.g. bicornuate uterus) or uterine scar (previous caesarean section, myomectomy, hysteroscopic surgery, curettage).
Premature contraction of the lower segment (causes a trapped placenta): use of intravenous ergometrine for postpartum haemorrhage (PPH) prophylaxis.
‘Since it is a verity indubitable, that the after birth remaining behind after the child is born, becomes a useless mass, capable of destroying the woman, we must take care that it be never left, if possible.’
The Diseases of Women with Child, and in Child-Bed. London: John Darby, 1683:p212