Maternal Iron Status in Early Pregnancy and Blood Pressure Throughout Pregnancy, Placental Hemodynamics and the Risk of Gestational Hypertensive Disorders.

BACKGROUND In non-pregnant populations, higher serum ferritin, which reflects high iron stores, is associated with an increased risk of hypertension. We hypothesized that a dysregulated maternal iron status in early pregnancy may lead to impaired gestational hemodynamic adaptations, leading to an increased risk of gestational hypertensive disorders. OBJECTIVE Examine the associations of maternal iron status with maternal blood pressure, placental hemodynamic parameters and the risks of gestational hypertensive disorders. METHODS In a population-based prospective cohort study among 5983 pregnant women, we measured maternal serum ferritin, transferrin saturation, serum iron and transferrin concentrations at median 13.2 weeks gestation (95% range 9.6, 17.6). Maternal blood pressure was measured in early-, mid-, and late pregnancy, and placental hemodynamic parameters in mid- and late pregnancy by ultrasound. Information on gestational hypertensive disorders was collected from medical records. We examined the associations of maternal early pregnancy iron status with maternal systolic and diastolic blood pressure, placental hemodynamic parameters and the risks of gestational hypertensive disorders using linear and logistic regression models. RESULTS Higher maternal early pregnancy serum ferritin concentrations were associated with higher systolic and diastolic blood pressure throughout pregnancy in the basic models (P-values < 0.05). After adjustment for maternal inflammation, sociodemographic and lifestyle factors, higher maternal early pregnancy serum ferritin concentrations were only associated with a higher early pregnancy diastolic blood pressure (0.27 (95% CI 0.03, 0.51) mmHg per SDS increase in serum ferritin) and with a higher mid pregnancy umbilical artery pulsatility index (P-value < 0.05). No associations were present with the risk of gestational hypertensive disorders. CONCLUSION No consistent associations of maternal iron status in early pregnancy with gestational hemodynamic adaptations or the risks of gestational hypertensive disorders were present. Further studies are needed to examine the potential role of iron metabolism in the development of gestational hypertensive disorders within higher risk populations.