OBJECTIVE To determine the effects of fasting during the month of Ramadan on fetal development and maternal serum cortisol and lipid profile. METHODS This study was performed in Obstetrics and Gynecology Department of Gaziantep University Hospital, between 23 September 2006 and 23 October 2006 (during the month of Ramadan). Thirty-six consecutive healthy women with uncomplicated pregnancies of 20 weeks or more, who were fasting during Ramadan, were included in the study group (group 1). The control group (group 2) consisted of 29 healthy pregnant women, who were not fasting during the study period. For evaluating Ramadan's effect on fetus, Doppler ultrasonography was performed on all subjects in the beginning and then once a week until the end of Ramadan for the following measurements: increase of fetal biparietal diameter (BPD), increase of fetal femur length (FL), increase of estimated fetal body weight (EFBW), fetal biophysical profile (BPP), amniotic fluid index (AFI), and umbilical artery systole/diastole (S/D) ratio. Maternal serum cortisol, triglyceride, total cholesterol, low-density lipoprotein (LDL), high-density lipoprotein (HDL), very low density lipoprotein (VLDL), and LDL/HDL ratio were also evaluated before and after Ramadan. RESULTS No significant difference was found between the two groups for the fetal age, maternal weight gain (kilogram), estimated fetal weight gain (EFWG), fetal BPP, AFI, and umbilical artery S/D ratio. In the fasting group, the maternal serum cortisol levels on day 20 were significantly higher than the initial levels obtained 1 week prior to Ramadan (p < 0.05). Although no significant increases were observed in total cholesterol and triglyceride levels in the fasting group, these increases were significantly higher than those in the control group (p < 0.05). LDL and VLDL levels showed a non-significant decrease at the end of the Ramadan. HDL levels showed a slight increase, but LDL/HDL ratios were significantly decreased in fasting group (p < 0.05). CONCLUSIONS The results of this study showed that maternal serum cortisol level was elevated while LDL/HDL ratio were decreased in healthy women with uncomplicated pregnancies of 20 weeks or more, who were fasting during Ramadan. No untoward effect of Ramadan was observed on intrauterine fetal development.