The investigators propose a Phase II interventional trial to investigate the role of Lactobacillus reuteri DSM 17938 on the intestinal motility and immune response of premature infants and further evaluate safety of the use of this probiotic in a population of premature infants.

Hypothesis Administration of Lactobacillus reuteri to premature infants will improve their intestinal motility when compared with infants receiving placebo. Primary Objective Evaluate the effects of L. reuteri in the intestinal motility by measuring the gastric emptying rate in infants before and after 21 consecutive days of administration of L. reuteri.

Secondary Objectives 1. Mechanisms of action of L. reuteri - L.reuteri impact in the host immune response by determining fecal cytokines, sIgA and calprotectin before and after 21 days of administration - L.reuteri rate of colonization after its administration.

2. Efficacy and safety of L. reuteri to premature infants - Clinical beneficial effects secondary to the administration of L. reuteri to premature infants. The following clinical outcomes will be identified and compared between groups:

• Number of gastrointestinal symptoms (regurgitation, vomiting, stasis)
• Days to full feeds. Number of days to reach full feeds defined as > 120cc/kg/day) x2 days or more.
• Days on parenteral nutrition
• Weight gain defined as the number of days needed to reach 150% of birth weight
• Length of hospital stay
• Any possible side effects and adverse events secondary to the administration of L. reuteri to premature infants.
• Incidence of late onset sepsis.
• Incidence and severity of necrotizing enterocolitis categorized by Bell's classification
• Use of antibiotics (number of days on antibiotics during the hospital stay)
• Mortality (at 28 days after birth and at hospital discharge).

Inclusion Criteria:

• Gestational age 30 - 32 weeks. Gestational age will be defined by the best estimate based on prenatal ultrasound in the first trimester, DLM and/or Balard Score after birth.

Exclusion Criteria:

• Cardiovascular or (respiratory) instability after 48 hours of age - Chromosomal anomalies.
• Major congenital anomalies (complex cardiac anomalies, congenital hydrocephalus, renal dysplasia)
• Congenital (e.g. jejunal atresia) and acquired (e.g. GI perforation) gastrointestinal pathology precluding oral feed and/or requiring major surgical or medical intervention
• Parental refusal
• Prior enrollment into a conflicting clinical trial. Conflicting clinical trial will be those in which the intervention could modify the outcome of the present study, for example studies that could alter the intestinal motility or the immune response of the premature infants.