Exposure to naturally occuring metals during early-pregnancy and pregnancy outcomes: results from the IoMum cohort

Abstract

Introduction: Environmental stimuli pose serious risks to the health of the mother and foetus. Frequent and daily exposure to naturally occurring metals makes it important to study possible impacts on pregnancy and newborn health. Aims: Characterize the level of exposure to Aluminium (Al), Lithium (Li), Barium (Ba), and Strontium (Sr), and its associations with anthropometric parameters of the newborn and the pregnancy outcomes. Methods: This was an observational study based on the IoMum cohort (trial registration #NCT04010708, ethical approval #292/17). Spot urine samples of eligible pregnant women attending the routine first-trimester ultrasound scan from April 2018 to April 2019 at Centro Hospitalar Universitário de S. João were analyzed through the inductively coupled plasma mass spectrometry in order to quantify the metals' urinary concentrations. Inclusion criteria were: gestational age between 10 weeks and 13 weeks plus 6 days, confirmed foetal vitality and signature of the informed consent. Results: Sample size was 349, corresponding to the amount of urine samples collected. The median urinary concentrations of the metals were (in µg/L): Al 8.3, Li 18.46, Ba 1.73, and Sr 100.68. Increased excretion of Al was found in healthcare and in hairdressing professionals. Regarding pre-pregnancy body mass index, median urinary metal concentrations consistently decreased from normal body mass index to obese women. In relation to dietary exposure, Sr urinary concentrations consistently decreased as the ingestion of milk increased. Finally, mothers of appropriate for gestational age newborns consistently presented with higher urinary excretion of Ba and Sr in comparison to small and large for gestional age newborns. Conclusion: Several sociodemographic factors may be associated with naturally occurring metals' exposure, although at levels not suspected of inducing important toxicity for the foetus or the mother.