In the past few years, maternal mortality from acid pulmonary aspiration (Mendelson's Syndrome) (1) has declined dramatically (Chapter 45). In the very first triennial Report on Confidential Enquiries into Maternal Deaths (1952) there were 32 deaths from Mendelson's Syndrome; in the 1967-69 Report there were 26 deaths; in the latest Report (1988-90) there were no clearly defined deaths from this condition (2).
This remarkable success can probably be attributed, in part, to the introduction of fasting regimens for parturients, the increasing use of regional anaesthesia for Caesarean section (CS), the universal adoption of cricoid pressure (Sellick's manoeuvre) (4) for CS under general anaesthesia and the introduction of the H2 antagonists into obstetric practice (Chapter 80). Perversely, this carefully audited success is now being used by midwives and maternal pressure groups as an example of the excessively dictatorial approach of obstetric anaesthetists in not allowing mothers to eat or drink during labour. They argue that prolonged fasting during labour has never been scientifically proven to influence pulmonary aspiration and that since most maternal anaesthetic deaths are now caused by difficult / failed intubation in the hands of inexperienced anaesthetists, it is illogical to continue to make women fast during labour.
Moreover, the metabolic consequences of fasting (e.g. ketosis, changes in lactate, insulin and Growth Hormone) might even be detrimental to the progress of labour. In addition, maternal intravenous hydration using 5% and 10% dextrose solutions has been shown to result in rebound neonatal hypoglycaemia. (3)
The safety of 'no feeding' policies during labour can never be disputed for those mothers who ultimately require an urgent or emergency Caesarean section. The effect of fasting or, indeed, feeding during labour on outcomes, both maternal and fetal, has never been evaluated in women receiving regional analgesia. A study on feeding during labour is currently in progress at St. Thomas' Hospital where parameters being evaluated include maternal and fetal metabolic effects of feeding, obstetric outcome, ultrasonic examination of the stomach (to measure residual gastric content) and maternal satisfaction.
References:
1. Mendelson CL. The aspiration of stomach contents into the lungs during obstetric anesthesia. Am J Obstet Gynecol 1946; 52:191
2. Report on the Confidential Enquiries into Maternal Deaths in England and Wales London:HMSO (1952-54), (67-69) and (1988-90)
3. Kenepp W, Sheeley WC et al. Fetal and neonatal hazards of maternal hydration with 5% dextrose before Caesarean section. Lancet 1982; i: 1150-1152
4. Sellick BA. Cricoid pressure to control regurgitation of stomach contents during induction of anaesthesia. Lancet 2:404, 1961