We retrospectively analyzed all late preterm deliveries (34 0/6 to 36 0/6 weeks of gestation) occurred in the Department of University Obstetrics and Gynecology of Foggia, Italy, in twenty-month period. The study was conducted in accordance with the guidelines in the Declaration of Helsinki and was approved by the committee of the Department of Medical and Surgical Sciences of the University of Foggia. Written informed consent was obtained from the patient’s guardian/parent/next of kin for the use of clinical data in order to search and for the publication of this report and any accompanying images.
The study group was compared with a control group consisting of full-term deliveries. Gestational age was determined by the first day of mother’s last normal menstrual period (LMP) with confirmatory ultrasonografy (US). When last menstrual period was unknown, dating was assigned by earliest US. The late preterm group was divided in 3 sub-groups: Group A: 34 0/6, Group B: 35 0/6, Group C: 36 0/6. None of patients enrolled had taken corticosteroid treatment before delivery. Abnormal pregnancies such as gestational diabetes, pregnancy related hypertension, placenta praevia and other medical and obstetrical disorders were excluded from the study. Admission criteria to the Neonatal Intensive Care Unit (NICU) include any of the following: hypoglycemia, jaundice, intraventricular hemorrhage, respiratory distress requiring respiratory support for longer than 24 hours, need for total parenteral nutrition, suspected sepsis, or significant hematologic abnormality (i.e., anemia, polycythemia, or thrombocytopenia), requirement for close observation as assessed by a neonatologist. Firstly, it was assessed if late preterm infants have a higher admission rate in NICU. Then, among late preterm sub-groups and full-term infants, it was assessed the rate of the major adverse outcomes as follows: hypoglycaemia: blood glucose less than 50 mg/dl (Bastek et al. 2008); intraventricular haemorrhage grades I-IV based on the extent of hemorrhage (Papile et al. 1978) , jaundice: hyperbilirubinemia requiring phototherapy (Petrova et al. 2006), respiratory distress syndrome/hyaline membrane disease (RDS) was typically defined as respiratory symptoms (eg, grunting, flaring, tachypnea, retractions), supplemental oxygen requirement, and NICU admission for further respiratory support, with the diagnosis verified by chest radiograph findings of reticulogranular patterns and air bronchograms (The Consortium on Safe Labor 2010), anemia: hemogolobin levels requiring transfusion.
Statistical analysis was performed by using the Z- test. An alpha value of 0.05 was used for assessing statistical significance. This value was appropriately adjusted by Bonferroni correction for taking into account the problems connected to multiple comparisons. The power analysis was performed in order to measure how the test is able to discriminate the groups. The statistical analysis was completed by assessing the power analysis on Z-test. Finally, the 95% confidence interval (CI) of the differences in the analyzed proportions was also calculated to evaluate the lower and upper bounds of the estimations.