Relationship between birth body weight<10.th centile (SGA) and insulin-like growth factor-i in the not-life threatened newborn: Relevance of birth chest circumference / birth body weight ratio

ABSTRACT

Birth chest circumference(CC) shows often, like birth gestational age(GA), tight direct relations to birth body weight(BW). However distinct connections of hypoxia/undernutrition with different body structures might be suspected based on brain-, heartand adrenal-sparing following intrauterine growth restriction and, postnatally, on higher chest size for body mass observed at high altitude. Low BW and hypoxia may be associated with circulating Insulin-like Growth Factor-I(IG1) lower levels. Relevance of human newborn(NWB) CC/BW ratio(i.e., CC through BW, CC/ BWR) to relationships between BW<=10.th centile for GA(SGA), and blood serum IG1(IG1s) was evaluated. NWBs with any among total parenteral nutrition, parenteral nutrition other than dextrose, blood component transfusion, postnatal corticosteroid-, catecholamine- or methylxantine-based treatments, life-threatening disease, diabetes mellitus(DM) or other endocrine diagnosis, malformation, and mother with DM were excluded. 78 included NWBs, all studied before covid-19 pandemic and from conception to study end near sea-level, had complete data for 1) same-day records at one of the first 5 postnatal days(x), 5 days after x(y) and 10 days after x(z) of postnatal age(PNA, unitday) and IG1s radioimmunoassay(unit=uM/dl), and for 2) gender (SEX), GA(unitcomplete week;extremes=28-42), GA<=36 present(PTB, n=46), CC(25th-75th centiles=27-32cm), BW(25th-75th centiles=1926-2942g), BW standard deviation scores(BW-SDS), and SGA(n=20)(computations;male SEX(n=43), SGA;condition absent=0, condition present=1). SPSS-27 software was used to generate GA-unrelated CC/BWR standardized residuals(CC/ BWRsr)(i.e., Linear regression procedure-Save pushbutton/ Standardized residual checkbox-Continue pushbutton/ regress CC/BWR on only GA). IG1s at x-y-z time-points was averaged (i.e., (x+y+z)/3;IG1sM). IG1sM normal score according to Van der Waerden(IG1sM-NS) resulted normally distributed. Mann- Whitney Test PTB did not differ significantly from non-PTB for CC/BWRsr;SGA showed significantly lower IG1sM than non- SGA. Spearman rank correlations between the following variable pairs are reported(Rho;significance) BW-SDS vs CC/BWR(-.361;p=.0012), BW-SDS vs CC/BWRsr(-.766;p<.0001), CC/BWR vs IG1sM(-.659, p<.0001), CC/BWRsr vs IG1sM(-.271, p=.0166). Partial correlation(pc) coefficient(pcc) of SGA pc with outcome IG1sM-NS in Multiple linear regression (MLR) was significant(t=-3.349, p<.0013, pcc=-.365) with SEX-GA-SGAPNAx as predictors, but was non-significant with SEX-GASGA- CC/BWRsr-PNAx as predictors (MLR R2, .486-.513, always significant). CC/BWRsr could be involved in inverse relationships between SGA and IG1sM-NS after controls including GA in NWBs free of life-threatenig disease.