The serum IgG level and body weight of premature infants have a relationship with gestational age and other factors. At 20 weeks, the level gradually increases, with a large amount of IgG passing through the placenta at 32 weeks of pregnancy. The fetal serum IgG concentration for gestational ages less than 32 weeks is below 4G/L ~ 2L. Foreign studies have reported a linear relationship between IgG and gestational age [L3J]. In China, it has also been reported that in preterm infants, IgG levels are positively correlated with mean gestational age [L5J]. This study also confirmed this point. Furthermore, body weight and serum IgG levels are positively correlated. Comparing the absolute value of the correlation coefficient between body weight and serum IgG levels and the absolute value of the correlation coefficient between gestational age and serum IgG levels (relative intensity comparison), the latter is greater than the former, indicating a closer correlation and greater severity compared to the former.
Analyzing the reasons, smaller gestational age leads to lower weight due to worse placental maturity, fewer Fc receptor numbers in placental tissue, and imperfect function, resulting in less IgG passing through the placenta. Weight and gestational week are not only closely related but also influenced by other factors. By comparison, gestational weeks are more stable, so the strength of the association between weight and IgG is less than the strength of the association between pregnancy days and IgG. When a pregnant woman is in a diseased state, such as hypertensive syndrome of pregnancy, malnutrition, or pre-existing maternal pulmonary and cardiac diseases, it can induce chronic placental hypoxia, thereby affecting placental function, leading to lower body weight, prematurity, and suppressed immune systems.
After birth, due to weaker barrier function, immature T.B lymphocyte function, and underdeveloped cellular immunity and humoral immune function compared to full-term infants, these infants are more susceptible to pathogen invasion [6J]. Therefore, it is necessary to improve immune function in premature infants through certain methods. Simultaneously, strengthening nursing care and preventing infections is key to improving the survival rate of premature and low-birth-weight infants.