Serum cobalt status during pregnancy and the risks of pregnancy-induced hypertension syndrome: A prospective birth cohort study

Cobalt (Co) is an essential trace element and has been suggested to be involved in blood pressure regulation, but few studies have focused on serum Co status during pregnancy and the risks of pregnancy-induced hypertension syndrome (PIH). The aim of this study was to prospectively assess the association between serum Co levels during pregnancy and the risks of PIH, and to explore how the maternal Co status contributes to the incidence of PIH. 3260 non-hypertensive women before pregnancy with singleton births in Ma'anShan birth cohort study (MABC) were recruited with the assessment of maternal Co concentrations, additionally, the levels of 7 inflammatory factors and 3 stress factors in placentas were also determined. Relative risks (RRs) [95% confidence intervals (CIs)] for the risks of PIH were assessed and the relationships between 10 factors and maternal Co status during pregnancy were evaluated as well. A total of 194 (5.95%) women were diagnosed with PIH. The concentrations of Co varied from the first trimester to the second trimester, and maternal serum Co concentrations during pregnancy were negatively associated with the incidence of PIH in a linear fashion. There was a clear trend in RRs according to decreasing exposure to Co levels in the second trimester (RRa=1.80, 95% CI (1.26, 2.56); RRb=1.73, 95% CI (1.21, 2.46) and RRc=1.43, 95% CI (1.02, 2.04) when low Co levels comparing with high Co levels before and after adjustment for confounders; and RRa=1.29, 95% CI (0.88, 1.88); RRb=1.28, 95% CI (0.87, 1.87) and RRc=1.25, 95% CI (0.86, 1.82) when medium Co levels comparing with high Co levels before and after adjustment for confounders). In addition, the trend for the first trimester was nearly identifical to those for the second trimester (RRa=1.35, 95% CI (0.94, 1.93); RRb=1.33, 95% CI (0.93, 1.91); RRc=1.22, 95%CI (0.86, 1.73) when low Co levels comparing with high Co levels before and after adjustment for confounders; and RRa=1.10, 95% CI (0.76, 1.60); RRb=1.13, 95% CI (0.77, 1.64) and RRc=1.12, 95% CI (0.77, 1.63) before and after adjustment for confounders). Interestingly, Co concentrations in the second trimester were also inversely associated with the levels of some inflammatory factors and all three stress factors in placentas. This prospective study suggested that lower maternal serum Co concentration in the second trimester may associate with the incidence of PIH in Chinese population. Additionally, the maternal Co concentrations in the second trimester could reduce inflammatory and oxidative damage to the placenta. Further evidence is needed to support the findings and assess the mechanisms underlying the association.