1. Metabolic changes associated with Ramadan fasting were studied in eleven Asian pregnant mothers. This was compared with a group of control mothers undergoing a normal physiological fast. 2. At the end of the Ramadan fast day there was a significant fall in glucose, insulin, lactate and carnitine, and a rise in triglyceride, non-esterified fatty acid and 3-hydroxybutyrate. When compared with the control group, none of the Ramadan mothers had a completely normal set of biochemical values at the end of the fast day. 3. Pregnancy outcome in the two groups was comparable. 4. We are wary of the metabolic departures from normal observed in the Ramadan fasting mothers. If asked we advise mothers to take up the dispensation from fasting during pregnancy which is allowed.