Historically, well...since the mid 1940s, women have been given nothing but ice chips (if that) during labor.
It all is due to Mendelson's Syndrome. Mendelson's syndrome is characterised by a bronchopulmonary reaction following aspiration of stomach contents during general anesthesia due to reductionof the reflexes in the thoat.. The main clinical features, which may become evident within two to five hours after anesthesia, consist of decreased oxygen in the body, and tachycardia (rapid heart beat), associated with a high blood pressure. It occurs predominantly in association with obstetric anaesthesia, particularly general anesthesia.
The thought here was that if there was nothing on the mother's stomach and she had to have an emergency cesarean that required general anesthesia (all of which is highly rare), then she would have little or no vomit and thus...no Mendelson's syndrome!
This practice has continued for years. However in March 2009, a study was published in the British Medical Journal (BMJ. 2009 Mar 24;338): "Effect of food intake during labour on obstetric outcome: randomised controlled trial." The conclusion was reached that consumption of a light diet during labor did not influence obstetric or neonatal outcomes in participants, nor did it increase the incidence of vomiting. Women who are allowed to eat in labor have similar lengths of labor and operative delivery rates to those allowed water only.
The study of 2426 participants does not tell of the overall feeling of more well-being from mothers who were allowed sustenance during labor nor does it talk about the stamina during second stage that women feel more of if they have had some nutrients during labor.
The important message here is: The conclusion was reached that consumption of a light diet during labor did not influence obstetric or neonatal outcomes in participants.
Thus, the evidence shows there is no hazard to eating and drinking lightly during labor.