2.1 Study Design
This is a case-control study, including 49 newborns from mothers with GDM in a reference maternal institution in Rio Grande do Norte (UFRN), Brazil, between January and October 2018. All anthropometric measurements including weight, length, and head/chest perimeter of the newborns were analysed and based shortly after birth, and then categorized according to the WHO.
The results of the outcomes of the newborns were also analysed and based on delivery and complication: Type of delivery (born via vaginal or lower segment cesarean section), gestational age by prematurity (<37 weeks), respiratory distress, apgar in the 1st and 5th minute, intensive therapy, jaundice, malformation, neonatal blood hypoglycemia and macrosomia (large for gestational age, defined as birth weight >4000 g). GDM was diagnosed according to the guidelines of the American Diabetes Association (ADA)18, with blood glucose changes between ≥ 92 mg/dL and < 126 mg/dL during prenatal care.
This study excluded: Stillbirth (defined as pregnancy loss >24 weeks gestation), spontaneous abortion (defined as pregnancy loss ≤23 weeks gestation), termination of pregnancy, loss of follow-up or transfer of care to another center before the childbirth.
The study was approved by the Ethics Committee of UFRN (CAAE 73305717.2.0000.5292). The institutions in which the data collection process was carried out gave their endorsement and authorization for the review of data sources. An informed consent form was signed by all pregnant women prior to data collection. All procedures were performed in compliance with the Declaration of Helsinki.
2.2 Control group
The control group included 45 newborns of mothers without GDM (blood glucose < 92 mg/dL post screening OGTT at 24 - 28 weeks) and no other comorbidities.
2.3 Blood plasma analysis by ATR-FTIR
The venous blood of the mothers when they were pregnant was collected and centrifuged for the separation of blood plasma. ATR-FTIR was used to analyze the absorbance biomolecules present in the blood plasma of pregnant women with GDM and their correlation with adverse neonatal outcomes. In order to obtain absorption by the spectrophotometer the biological range of the spectral region analyzed was from 1,800 cm-1 to 900 cm-1. Subsequently, biomolecule absorption was analyzed by the mathematical model Genetic Algorithm (GA) associated with Linear Discriminant Analysis (LDA) and compared with plasma samples from mothers without GDM, as described by Paraskevaidi et al., (2017)19 and Neves et al., (2016)20, with some modifications.
Statistical Analysis
The Shapiro-Wilk normality test was applied to verify the adherence of continuous variables to the normal distribution. Descriptive analysis of the variables that obtained adherence to the normal distribution was performed by the mean and standard deviation (Mean ± SD). For variables that did not present normal distribution in either group, the median and the 25th and 75th percentiles were used. For categorical variables, the analysis was performed using absolute and relative frequencies. Student's t-test for independent samples was applied for continuous variables that presented normality. The Mann-Whitney nonparametric test was used to compare the differences between the distributions of variables that did not show normality. The chi-square test was used to analyze the association between type of delivery and categorical variables. In situations where the table cells presented expected frequencies below five, Fisher's exact test was applied. A significance level of 5% was adopted for all analysis. The software used for the analysis was the Statistical Package for the Social Sciences (Chicago, USA), version 22.0.