The increase in obesity among women of reproductive age has resulted in an elevated prevalence of pregnant women with obesity and overweight. A limited group of biometric indexes were used in an attempt to categorise pre-pregnancy obesity that could achieve high sensitivity and specificity to detect adverse pregnancy outcomes. Adult body mass index (BMI) over 30 kg/m2 has been used more frequently but with conflicting results among studies that addressed the index as a GDM predictor.1, 2, 3 The Child Growth Standard (CGS) index has been used as a predictor for certain outcomes, including the need for a caesarean among pregnant adolescents. Likewise, body surface area (BSA) was employed as a predictive measure for the development of gestational diabetes mellitus (GDM) in a cohort of pregnant women in Finland, all of whom had biometric data since birth. The study revealed a negative correlation between BSA and GDM, indicating that pregnant women with lower BSA scores were more likely to be affected by GDM. The researchers hypothesised that unfavourable conditions since pregnancy, leading to maternal restricted growth, resulted in a reduced count of pancreatic beta cells from birth, thereby elevating the future risk of GDM.4

Maternal abdominal adipose tissue assessed by ultrasound has been shown to be an accurate and low-cost method for predicting abnormal pregnancy outcomes, particularly GDM,5, 6, 7, 8, 9 pre-eclampsia and preterm birth,10 metabolic syndrome,5 abnormal arterial blood pressure5, 11 and abnormal newborn weight.12 Two maternal abdominal sites were selected to access maternal adipose tissue, the maternal epigastric site5, 13 and the periumbilical site6, 8 with the first being used during all three trimesters and the second limited to evaluations prior to twenty weeks due to gravid uterus growth.

Recently a new GDM predictive index has been proposed using the amounts of maternal epigastric adipose tissue measured by ultrasound and maternal height, called the body fat index (BFI) as a substitute to pre-pregnancy BMI.14 The reported predictive accuracy for GDM was found to exceed that of pre-pregnancy BMI.

However, the study was conducted late into pregnancy, where the deleterious effects of dysglycaemia are already established. Additionally, the BFI was calculated with scores from the maternal epigastric site rather than both known adipose-related sites. Finally, the study did not report the predictive analysis of the new index for GDM as an outcome, including sensitivity, specificity, or the predictive values. As such, the objective of this study was to evaluate the predictive capacity of the BFI index with GDM as the outcome of interest. Most importantly, we aim to determine BFI index using maternal abdominal fat scores from the epigastric and perumbilical sites, indicating GDM risk thresholds for both sites. Ultimately, our study will assess the comprehensive performance of the new index in comparison to the traditionally utilised pre-pregnancy BMI.