A prospective, randomized case-controlled trial was conducted in infants with a gestational age of 30 to 37 weeks and a birth weight between 1500 to 2500 g. The study group received S. boulardii supplementation, 50 mg/kg twice daily, compared to no intervention in the control group. The primary outcomes were short term growth parameters including weight gain, linear growth, head and chest circumference, and secondary outcomes were clinical outcomes, feeding intolerance and complications.