Investigation of immune parameters in infants with small for gestational age (SGA), large for gestational age (LGA), and appropriate for gestational age (AGA)

Babies with small for gestational age (SGA) or large for gestational age (LGA) birth weights differ metabolically, developmentally, and immunologically from babies with appropriate for gestational age (AGA) birth weights. SGA babies have a higher risk of infection, jaundice, intraventricular hemorrhage, respiratory distress, and hypoxic-ischemic encephalopathy. Similarly, preterm babies (those born before 37 weeks) have a higher incidence of infections compared to term babies. Since the increased risk of infection is primarily related to a weaker immune system, the aim of this study was to compare the immune system parameters of term/preterm and AGA/LGA/SGA babies. The study included 44 babies born at Hacettepe University Faculty of Medicine Hospital between July 2023 and September 2023, with consent obtained from their families. Of the 44 babies, 9 were classified as SGA, 6 as LGA, and 29 as AGA. The patients were evaluated three times: at birth, in the 2nd postnatal month, and in the 7th month. At birth, cord blood samples were taken to measure complete blood count, lymphocyte subgroups, lymphocyte proliferation tests, immunoglobulin G-A-M levels, anti-HBs, and tetanus immunoglobulin G levels. In the 2nd and 7th postnatal months, immunoglobulin G-A-M levels, anti-HBs, and tetanus immunoglobulin G levels were re-measured. Additionally, during birth, immunoglobulin G-A-M levels, anti-HBs, and tetanus immunoglobulin G levels were measured from the mothers. All babies were vaccinated according to the national vaccination schedule. No significant differences were found between the tetanus immunoglobulin G, lymphocyte subgroups, or immunoglobulin levels. Although the number of patients from whom proliferation tests could be obtained was small (13 of 44 patients), the proliferation response of cord blood lymphocytes was found to be high, while their response to stimulation was low. In the second month, the anti-HBs value was <100 IU/L in all SGA babies. The 2nd month anti-HBs average in the term-SGA group was lower compared to the term-AGA group. However, by the 7th month, the anti-HBs value of all babies was >100 IU/L. Babies whose mothers were anti-HBs negative had lower anti-HBs vaccine responses at the 2nd month. The fact that SGA babies had lower vaccine responses compared to AGA and LGA babies indicates that their immune system functions are weaker. Therefore, larger-scale studies investigating the immune systems of SGA babies are needed to achieve optimal vaccine responses