Principles of intrapartum skills

33. Principles of intrapartum skills

examination of the placenta


CHAPTER CONTENTS




Structure and appearance235


Fetal surface of the placenta 235


Maternal surface of the placenta 237


PROCEDURE: examination of the placenta 237


Cord blood samples 238


Disposing of the placenta238


Role and responsibilities of the midwife239


Summary239


Self-assessment exercises239


References239

LEARNING OUTCOMES
Having read this chapter the reader should be able to:


• describe the structure and appearance of the placenta at term


• describe how the placenta is examined


• discuss the significance of the information obtained from the examination


• discuss the role and responsibilities of the midwife in relation to examining the placenta.



Examination of the placenta following delivery is an important skill undertaken by the midwife to reduce the occurrence of both postpartum haemorrhage and infection. This chapter describes the structure and appearance of the placenta, discussing the significance of deviations, and concluding with the procedure for undertaking examination of the placenta. It concludes with a brief discussion concerning disposal of the placenta.



Structure and appearance


The placenta is a disc-shaped structure that has both maternal and fetal surfaces. At term, the placenta weighs approximately 500–600 g (about one-sixth of the baby’s weight), has a diameter of 15–20 cm and is 2–3 cm thick. Early cord clamping may result in the placenta being proportionally heavier, whereas delayed cord clamping can produce a placenta that is proportionally lighter, due to the amount of blood transfused from the placenta to the baby at delivery. A larger placenta may be associated with maternal diabetes and multiple pregnancy, a smaller placenta with chronic intrauterine growth restriction.

Occasionally the placenta may develop with an abnormal structure and appearance such as a circumvallate placenta. The placenta enlarges beneath the endometrial surface and the embryonic sac enlarges above it; the endometrium between the two is compressed and obliterated resulting in an acellular membrane, which may affect the attachment of the placenta to the decidua, increasing the risk of placental abruption. The placenta has a thick, grey/white raised ring around the central part of the fetal surface, caused by the fetal membranes folding back on themselves.


Fetal surface of the placenta










B9780702031465000339/gr1.jpg is missing
Figure 33.1 •
Bipartite placenta


Blood vessels, branches of the umbilical vein and arteries are clearly visible, spreading outwards from the point of cord insertion, usually centrally or slightly off centre (Fig. 33.2A,B). A cord inserted at the edge of the placenta – a ‘battledore’ insertion (Fig. 33.2C) – is usually insignificant, although the attachment may be fragile, increasing the risk of detachment during controlled cord traction. Rarely the cord is inserted into the membranes – a ‘velamentous’ insertion (Fig. 33.2D) – with vessels running through the membranes to the placenta. The attachment can be very fragile, resulting in detachment during controlled cord traction. The vessels may overlie the cervix (‘vasa praevia’) and if ruptured during spontaneous or artificial rupturing of the membranes will result in massive fetal haemorrhage.








B9780702031465000339/gr2.jpg is missing
Figure 33.2 •
Cord insertions. A Central. B Eccentric. C Battledore. D Velamentous



Jun 18, 2016 | Posted by in MIDWIFERY | Comments Off on Principles of intrapartum skills
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