2.6.2 Pharmacological pain relief in labour

Pharmacological methods of pain relief have gained ample application, especially in the developed countries. The effects of several techniques have been investigated by clinical trials; the benefits of pain relief became obvious, but the possible adverse effects on mother or infant have received less attention.

Systemic agents

A number of drugs have been and are being used for pain relief: opioid alkaloids, of which by far the most popular is pethidine, followed by phenothiazine derivatives (promethazine), benzodiazepines (diazepam) and others. In some countries inhalation analgesia for normal labour has decreased in recent years (it has been replaced by epidural analgesia); the most commonly used agent is nitrous oxide combined with 50 percent oxygen. All these agents can provide reasonable pain relief, but at the cost of unwanted side-effects (Dickersin 1989). Maternal side-effects of pethidine are orthostatic hypotension, nausea, vomiting, and dizziness. All of the systemic drugs used for pain relief cross the placenta and all except nitrous oxide are known to cause respiratory depression in the baby and neonatal behavioural abnormalities, including reluctance to breast-feed. Diazepam can cause neonatal respiratory depression, hypotonia, lethargy and hypothermia (Dalen et al 1969, Catchlove and Kafer 1971, Flowers et al 1969, McCarthy et al 1973, McAllister 1980).

Epidural analgesia

Of the different techniques of regional analgesia (epidural, caudal, paracervical, spinal) epidural analgesia is the method most widely used in normal labour. Its effects have been investigated in a number of trials, all of which compare epidural analgesia with other techniques of pain control (Robinson et al 1980, Philipsen and Jensen 1989, 1990, Swanstrom and Bratteby 1981, Thorp et al 1993). It provides better and more lasting pain relief than systemic agents. The adoption of epidural analgesia in obstetric care is resource-intensive and calls for several important facilities: labour and delivery should take place in a well-equipped hospital, the technical apparatus should be sufficient, an anaesthetist should be available at all times and constant skilled supervision of the mother is called for.

With epidural analgesia there is a tendency for the first stage of labour to be somewhat longer, and for oxytocin to be used more frequently. In several reports and trials the number of vaginal operative deliveries was increased, especially if the analgesic effect was maintained into the second stage of labour, thereby suppressing the bearing-down reflex. In a recent American trial the number of caesarean sections was increased when epidural analgesia was used, especially when the epidural was started before 5 cm dilatation (Thorp et al 1993). There is a paucity of data from randomized trials on possible effects of epidural analgesia on either mother or baby in the long term. No randomised trial compared epidural analgesia to “no pain control” or a non-pharmacological method, all comparisons are between different methods of epidural analgesia, or different methods of pharmacological pain relief. The main effect measured in the trials was the degree of pain relief, but in none of the trials of epidural analgesia was maternal satisfaction with childbirth measured. An observational study (Morgan et al 1982) suggests that there is no direct relation between pain relief and satisfaction. In a trial of birth centre care in Sweden the use of epidural analgesia and other methods of pharmacological pain relief was significantly lower in the birth centre group compared with standard care; nevertheless the attitude towards labour pain when asked two months after the birth was not different between the groups. Apparently many of the women regarded pain in labour in a positive light, as a feeling of achievement, which illustrates the different character of pain in childbirth compared to pain related to illness (Waldenstrnd Nilsson 1994). In a study of new mothers, support by caregivers had a positive effect on women’s total birth experience, while pain relief did not explain any of the variations in women’s responses (Waldenstrt al 1996).

There is little doubt that epidural analgesia is useful in complicated labour and delivery. However, if epidural analgesia is administered to a low-risk pregnant woman, it is questionable whether the resulting procedure can still be called “normal labour”. Naturally, the answer depends on the definition of normality, but epidural analgesia is one of the most striking examples of the medicalization of normal birth, transforming a physiological event into a medical procedure. The acceptance of this transformation is largely determined by cultural factors. For instance, in Britain and the USA a large number of low-risk pregnant women deliver under epidural analgesia, while in the vast majority of developing countries very many deliveries take place at home, without any pharmacological pain control. This is not merely a contrast between developing and developed countries: in the Netherlands more than 30% of all pregnant women give birth at home without any pharmacological pain control, and even if they deliver in hospital only a minority of low-risk women receive pain relieving medication (Senden et al 1988).

In conclusion, in the care surrounding normal birth, non-pharmacological methods of pain relief, such as paying personal attention to the labouring woman, are of utmost importance. Methods requiring a large number of technical facilities like epidural analgesia, are only applicable in well-equipped, well-staffed hospitals. In many countries these technical facilities are not generally available, especially for normal childbirth. However, the demand for these methods is in large measure culturally determined, the quality of care in normal delivery is not dependent on the availability of these technical facilities. They are no part of essential care during childbirth. Pharmacological methods should never replace personal attention to the labouring woman and tender loving care.