Background: labor is a clinical diagnosis characterized by regular, painful uterine contractions that increase in frequency and intensity is associated with progressive cervical effacement or dilatation. More specifically, it is associated with a change in the myometrial contractility pattern from irregular "contractures" (long-lasting, low-frequency activity) to regular "contractions" (high-intensity, high frequency activity). Aim of the work: it was to determine if fetal head circumference and fetal weight could predict the rate of caesarian section and operative vaginal deliveries in nulliparous women in labor. Patients and Methods: this study was carried out at Al Alamein Hospital from January 2017 to January 2018 on two hundred (200) primigravida women; their ages ranged from 20 to 30 years and the gestational ages ranged from 38-40 weeks with normal singleton pregnancy with cephalic presentation in labor. Results: there were highly statistically significant relations between mode of delivery and fetal head circumference and estimated fetal weight as p value (0.001).it was found that large fetal head circumference relative to maternal pelvic diameter is the main cause of prolonged labor and therefor increased risk of primary caesarian section. Conclusion: the numerical data have a significant relation between intra partum head circumference and fetal weight and the incidence of primary caesarian section, maternal and fetal complications. Recommendations: according to numerical results obtained from this study. The study recommends strict labor monitoring by partogram in cases where fetal head circumference is more than 35cm or fetal weight is more than 3950gms.