Near‐Infrared (NIR) Spectroscopy of Amniotic Fluid (AF) Distinguishes Between AGA and LGA Infants

Abstract

BackgroundNIR of AF has been used to characterize fetal lung maturity and prematurity. However, this approach has been seldom used to classify infants according to birth weight for gestational age.ObjectivesWe explored the possibility that NIR of 2nd trimester AF could identify early metabolomic differences between appropriate‐ (AGA, n=494) and large‐ (LGA, n=51)‐for‐gestational age infants. A secondary objective explored whether these AF profiles differed by maternal pre‐pregnancy BMI: normal BMI<24.9kg/m2 (n=310) vs overweight/obese BMI>25 kg/m2 (n=168).MethodsEight NIR functional groups (1600‐2400nm) were selected (CH, SH, POH, ROH, amide, amine, lactate and glucose); their values and calculated ratios were compared among experimental groups using Mann‐Whitney U‐test and Kruskal‐Wallis one‐way ANOVA test, followed by post‐hoc comparisons.ResultsThirteen functional group ratios differed. LGA infants had higher AF glucose relative to CH, SH, POH and ROH and higher AF amines relative to POH, ROH, glucose and amides. In contrast, AGA infants had higher POH and ROH relative to glucose, amines and amides and higher CH:glucose and SH:glucose compared to AF of LGA infants. When subdivided by BMI categories, only AGA infants of overweight/obese mothers had higher AF glucose compared to normal weight mothers; surprisingly this maternal BMI‐based difference did not exist for LGA infants.ConclusionNIR spectral profiles of 2nd trimester AF differed between LGA and AGA infants but maternal BMI was not sufficient to fully explain early 2nd trimester metabolic perturbations.