Studies on maternal body fat distribution in relation to infant outcomes

Sammanfattning: Background: Overweight and obesity are common amongst pregnant women and associated with adverse pregnancy outcomes for both the mother and the infant. Today, body mass index (BMI), not accounting for body fat distribution, is used for risk stratification during pregnancy. We hypothesize that maternal central adiposity is associated with pregnancy complications, independent of BMI, and that blood-based protein biomarkers differ between women with dissimilar body fat distributions, reflecting biological discrepancies.Objectives: This thesis aims at 1) systematically reviewing the current knowledge on the relation of maternal central adiposity with infant outcomes, 2) evaluating the association of ultrasound measured early mid pregnancy visceral and subcutaneous fat depths with infant birth size and adverse neonatal outcomes, and 3) investigating the relations of fat depth measures with maternal blood-based protein biomarkers. Methods: A systematic review was performed including six databases searched from inception until November 2019. Studies evaluating maternal central adiposity in relation to infant outcomes were included. Two cohort studies were conducted during 2015–2018 at Uppsala University Hospital. Visceral and subcutaneous fat depths were measured by ultrasound at the second-trimester anomaly scan. Fat depths of 2,498 women were evaluated in relation to infant birth size. Body mass index and fat depths of 2,771 women were evaluated in relation to neonatal hypoglycaemia, a composite of adverse neonatal outcomes (5-minute Apgar score <7, umbilical artery pH ≤7.0, or admission to neonatal intensive care unit), and the individual components of the composite outcome. Olink Cardiovascular II panel was used to analyse 92 blood-based protein biomarkers in 201 pregnant women. The protein concentrations were evaluated in relation to the ultrasound measured fat depths.Results: The systematic review demonstrated associations of maternal central adiposity with infant birth size and caesarean section. The results of the cohort studies showed an association of early mid pregnancy visceral fat depth with infant birth size. Additionally, BMI (but not fat depths) was associated with neonatal hypoglycaemia and adverse neonatal outcomes. Four blood-based protein biomarkers differed between pregnant women with dissimilar body fat distributions.Conclusions: Early mid pregnancy visceral fat depth is associated with infant birth size and may be useful in models predicting infant macrosomia. However, more research is needed to determine the usefulness of fat depth measures in addition to BMI as markers of adverse neonatal outcomes. Further research on blood-based biomarkers might enlighten biological mechanisms linking maternal body fat distribution types to neonatal outcomes.