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This Can Be Clinically Manifest By A Lengthening Of The Cord But No ...

This can be clinically manifest by a lengthening of the cord but no subsequent delivery of the placenta. In these circumstances the placental site can continue to bleed and the uterus can fill with blood, which distends the uterus and thereby increases the tendency for the placental site to bleed further. This clearly has very significant implications for the mother. (Neilson J et al. 2003)


There are other issues which impact on the foetal and maternal wellbeing in this stage of the delivery but these are generally not a feature issues relating to the active or passive management of the third stage of labour and therefore will not be considered further.

There are a number of other factors which can influence the progress of the third stage of labour and these can be iatrogenic. Concurrent administration of some drugs can affect the physiology of the body in such a way as to change the way it responds to normal physiological processes. On a first principles basis, one could suggest that, from what we have already discussed, any agent that causes relaxation of the myometrium or a reduction in uterine tone could potentially interfere with the efficient contraction of the uterine musculature in the third stage and thereby potentially increase the incidence of post partum haemorrhage.
Beta-agonists (the sympathomimetic group) work by relaxing smooth muscle via the beta-2 pathway. The commonest of these is salbutamol. When given in its usual form of an inhaler for asthma, the blood levels are very small indeed and therefore scarcely clinically significant but higher doses may well exert a negative effect in this respect. (Steer P et al. 1999)

The NSAIA group have two potential modes of action that can interfere with the third stage. Firstly they have an action on the platelet function and can impair the clotting process which potentially could interfere with the body's ability to achieve haemostasis after placental delivery. (Li D-K et al. 2003)

Secondly their main mode of therapeutic action is via the prostaglandin pathway (inhibitory action) and, as such they are often used for the treatment of both uterine cramping, dysmenorrhoea and post delivery afterpains. (Nielsen G L et al. 2001)

They achieve their effect by reducing the ability of the myometrium to contract and, as such, clearly are contraindicated when strong uterine contractions are required, both in the immediate post partum period and if any degree of post partum haemorrhage has occurred.

Other commonly used medications can also interfere with the ability of the myometrium to contract. The calcium antagonist group (e.g. nifedipine) are able to do this (Pittrof R et al. 1996) and therefore are changed for an alternative medication if their cardiovascular effects need to be maintained. (Khan R K et al. 1998)

We should also note that some anaesthetic agents can inhibit myometrium contractility.

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