Induction of labour is the artificial starting of labour before it begins spontaneously. The exact reason for the onset of labour is not known and, therefore, it is not possible to imitate precisely the way in which nature initiates labour. There are many reasons why a doctor may wish to induce labour before it commences spontaneously and various methods are used.
Methods used in Induction of Labour
Artificial Rupture of the Membranes
This has for many years been the most popular method of inducing labour. The membranes just inside the internal os of the cervix are perforated by gently introducing a sharp object or a pair of forceps through the cervical canal and some of the amniotic fluid can then drain away. This small procedure is easily accomplished without any pain or discomfort. The drainage of amniotic fluid from within the cavity of the uterus results in alteration of the pressure inside the uterus and it is thought that this initiates labour. In any event, labour will begin fairly soon after the membranes have been ruptured artificially and the nearer the woman is to her expected date the earlier labour will commence. When a woman is at or near term then labour starts within a few hours.
Oxytocic drugs are a group of drugs which have a direct action upon the uterus itself and will provoke or stimulate the uterus into rhythmic contractions and, therefore, into labour. The first of the oxytocic drugs used was pitocin, or pituitary extract, from the pituitary gland (a small gland situated at the base of the brain). This was given by means of intravenous drip, intramuscular injection or by mouth. In recent years the use of pitocin tablets, which are sucked to absorb the hormone from the mouth, has been replaced by the use of more reliable syntocinon intravenous infusions.
Ergometrine (either alone or as syntometrine) is a powerful oxytocic drug but, since it makes the cervix contract as well as the uterus, it is not used for the induction of labour because during labour dilatation of the cervix is required.
Syntocinon is now the standard drug for induction of labour. The dose can be accurately measured and administered by a painless intravenous drip either dircctly from a bottle or through an accurate antometric pump.
Prostaglandins are so named from their original isolation from extracts of animal prostate gland. They comprise a large group of hormones found in various organs of both male and female bodies. Some hormones of this group have been found to stimulate strongly the pregnant uterus and they are now being used in many centres for the induction of labour. They may be given orally as tablets or liquid or intravenously in a drip. They may be given vaginally to prepare a tightly closed cervix, for induction later or even to initiate labour.
A dose of castor oil is the well-tried and outdated method of inducing labour. Even a large dose fails unless labour is imminent, but has the side-effect of producing severe colic and profuse diarrhoea usually without any sign of labour.
Oil, bath and enema. This was the traditional, though ineffective, method of inducing labour and is no longer used. The administration of a large dose of castor oil was followed after a few hours by a warm enema and then the treatment was completed by the woman having a hot bath. Not only was this ineffective, but it also resulted in the woman being exhausted, dehydrated and somewhat demoralized before labour had even begun.
There are many other methods of inducing labour that have been practised over the centuries and some of which are still practised today.
Choice of Method of Induction
The choice of the method of induction to be used in any particular instance will rest with the obstetrician concerned and his selection will vary from person to person according to her particular requirements. The method most frequently performed is a combination of the above, consisting of an enema, followed by artificial rupture of the membranes, which in turn is followed by the administration of one of the oxytocic drugs, usually syntocinon, by a continuous intravenous drip. Labour nearly always begins within a very short time and proceeds normally.
Indications for inducing Labour
The indications for inducing labour may be either medical or social.
The medical reasons for inducing labour before it starts spontaneously may vary enormously. Pre-eclampsia, hypertension, postmaturity, placental insufficiency, diabetes, Rhesus incompatibility are just a few of the many reasons why the obstetricians may wish to induce labour.
Most authorities say that there are no social indications for the induction of labour and these have long been frowned upon in Britain. By social indications one means that labour is induced for the convenience of either the patient or the doctor. The objection to this is mainly traditional and dates back to the time when induced labour was not as safe as labour which began spontaneously. The induction of labour today, however, is completely safe, providing that the woman is at or near term and everything else is completely normal. Labour can be induced by means of syntocinon given, by a continuous drip into a vein and if this is accompanied by artificial rupture of the membranes then the onset of labour is assured.
If a woman is suffering from Rhesus incompatibility and it is known that her baby is going to need to have its blood changed as soon as it is delivered, then labour is induced so that the delivery occurs at a convenient hour during the week when the anaesthetist, the paediatrician and the laboratory are readily available. Every effort is made to ensure that such a woman is not delivered at midnight on a Saturday. This is an induction of labour done for a medical reason at a social time convenient to the doctors and the laboratory.
Now that the induction of labour is perfectly safe it is obvious that it will be used more and more frequendy in order that doctors and nurses can look after their patients during the hours of daylight when they themselves are fresh and when all the ancillary services they might require are readily and easily available, rather than deliver women during the night when they themselves are tired and when the ancillary services are not so readily available. A doctor or midwife who has been up for most of the night still has to work the next day !
Labour after Induction
After induction labour proceeds completely normally. An induced labour does not last any longer than a labour which commences spontaneously. An induced labour is not more painful than a labour which begins spontaneously. The chances of a normal delivery are just the same if labour has been induced as if it had begun spontaneously. Induced labour does not adversely affect die baby so long as appropriate steps are taken to ensure that labour begins within 24 hours after the membranes have been artificially ruptured.