Six hundred pregnant women aged from 20 to 40 years old with singleton living healthy fetuses undergoing elective lower segment caesarean section (LSCS); defined as LSCS done before onset of labor pains, will be enrolled in the study. They will be randomized into three groups: group A in which 200 women will receive IV ceftriaxone (2g) 60 minutes before skin incision, group B in which 200 women will receive IV ceftriaxone (2g) immediately with skin incision \& group C in which 200 women will receive IV ceftriaxone (2g) immediately after umbilical cord clamping. Randomization will be done using computer generated random numbers.

Another inclusion criterion includes gestational age (GA) more than 37 weeks gestation. Patients on immunosuppressant drugs, received any antibiotic prophylaxis (within 10 days), suffer any chronic illness (e.g. diabetes mellitus or renal disease) or who experienced any obstetric complication in the current pregnancy (e.g. antepartum hemorrhage \& rupture of membranes) will be excluded from the study. Additional exclusion criteria include previous history of more than two laparotomies, maternal BMI more than 28 \& any maternal febrile illness within 10 days from the procedure. Patients who are known to be allergic to penicillin or cephalosporin will be also excluded (all patients will receive 100 mg of ceftriaxone as a test dose before participation in the current study). The study was approved by the Hospital Ethical Committee. All participants will provide an informed consent after explaining the aim and potential hazards of the study.

For all patients, full history will be taken followed by complete physical examination, obstetric ultrasound \& routine preoperative investigations. GA is established by menstrual dates then confirmed by obstetric ultrasound. Spinal anaesthesia will be given for all patients. All cesarean sections will be done by ob/gyn residents under the supervision of senior staff obstetrician using the following technique: Pfannenstiel skin incision, transverse lower uterine segment incision, two-layer closure of the uterine wall, closure of both parietal peritoneum \& rectus sheath \& skin closure (using prolene 3/0 suture). Primary maternal outcome includes postoperative endometritis (diagnosed if maternal axillary temperature ≥ 38°C for at least 48 hours, uterine tenderness, infected lochia \& leukocytosis).Secondary maternal outcomes include wound infection (diagnosed if there is induration, redness, hematoma, seroma or purulent discharge at the incision site) \& urinary tract infection (diagnosed if there frequency, dysuria, suprapubic or loin pain \& positive urine culture). Prolonged postoperative hospital stay (more than 2 days) will also be recorded. The infectious morbidity evaluation will be done by ob/gyn residents who will be blinded to the study group of the patient. Neonatal outcomes include immediate antibiotic adverse effects (diarrhea \& rash), neonatal sepsis (diagnosed by clinical signs, leukocytosis, C-reactive protein\& positive blood culture), neonatal intensive care unit (NICU) admission (entailing the length of stay) \& neonatal death. All neonates will be examined by an expert neonatologist who will be blinded to study group of the neonate's mother. On discharging all patients, a brief summary about symptoms and signs of the above mentioned infectious \& neonatal complications will be given and they will be instructed to contact any of the authors immediately if any happens. Patients will be reexamined after 1 week (skin stitch removal appointment) \& 4 weeks (contraception counseling appointment) following the CS.