FMT as a preventive measure for NEC in premature infants

Inclusion Criteria:

* Preterm infants hospitalized in the intensive care unit and neonatal pathology unit during the study period

  1. 1\. Born naturally or by cesarean section between:

     1. 24 0/7 and 36 6/7 weeks of gestation
  2. Age \>48 hours, a minimum of 24 hours after completion of antibiotic therapy and up to day 14 for newborns \<35 weeks of gestation and up to day 6 for newborns \>35 weeks of gestation
  3. Newborns born in and out of hospital
  4. Parental consent to participate in the study

Exclusion Criteria:

1. Occurrence of congenital defects of the gastrointestinal tract preventing proper intestinal passage (esophageal atresia, duodenal atresia, rectal atresia, tracheo-esophageal fistulas) and occurrence of genetic diseases diagnosed prenatally or at birth (trisomies, other genetic syndromes).
2. Gastrointestinal perforation
3. Food allergy with anaphylactic shock
4. Participation in another clinical trial that may affect the final outcome of the planned intervention

Temporary exclusion criteria

If at least 1 of the following occurs before FMT and up to 14 days of age:

1. Intolerance to oral feeding, based on the assessment of the qualifying physician on the day of FMT:

   * painful bloating in the abdomen and/or visible bowel loops, blood in the stools,
   * delayed gastric emptying: two consecutive episodes exceeding \>50% of the volume of the previous serving, 2 or more consecutive episodes of retention / vomiting / regurgitation of biliary contents / duodenal contents/ blood - episodes not related to anxiety, delayed bowel movements, possibility of swallowing blood during childbirth or from damaged nipples, abnormality of the positioning of gastric tube, bleeding from the nose
2. Suspected NEC:

   * clinical signs typical for NEC - Bell criteria, redness/bruising of the anterior abdominal wall, palpable abdominal resistance, hypotension; laboratory signs: hyponatraemia, metabolic acidosis, thrombocytopenia, increased inflammation parameters)
3. Antibiotic therapy during planned FMT treatment
4. Clinical signs of infection or significantly elevated inflammatory parameters - If at least one of the following clinical signs and/or more than 1 laboratory sign occurs:

   • Clinical signs of infection: Hemodynamic instability (hypotension, tachycardia, peripheral circulatory disturbances (by age standards), thermoregulatory disturbances, fever\>38 deg C, hypothermia \<36 deg C) Apathy, lethargy, convulsions Apneas, deterioration of respiratory capacity

   • Laboratory signs of infection:

   Elevated inflammatory parameters:
   * leukocytosis \<5 i \>30x109/L up to 48 hours of life (HoL) and \<5 i \>20x109/L \>48 hours of life, the band neutrophil : total neutrophil (I:T) ratio of \>0.2 for \>34 weeks of gestation and \>0,16 for \<34 weeks of gestation
   * CRP (C-reactive protein) level \>0.05mg/l (at the norm up to \<0.05-1mg/l),
   * PCT (procalcitonin) level (\>72 HoL) \> 0,5-1ng/ml (at the norm up to \> 0,5-1ng/ml); Platelet count \< 50 thousand, coagulopathy positive cultures of normally sterile body fluids

     * Radiological evidence of infection, including systemic e. g. gallbladder bed swelling, unexplained sudden echocardiographic pulmonary hypertension