Background Phthalates are associated with increased blood pressure in children. Large exposures to di-(2-ethylhexyl) phthalate (DEHP) among premature infants have been a cause for concern. Methods We conducted a prospective observational cohort study to determine if DEHP exposures are related to systolic blood pressure (SBP) in premature infants, and if this exposure is associated with activation of the mineralocorticoid receptor (MR). Infants were monitored longitudinally for 8 months from birth. Those who developed idiopathic hypertension were compared with normotensive infants for DEHP exposures. Appearance of urinary metabolites after exposure was documented. Linear regression evaluated the relationship between DEHP exposures and SBP index and whether urinary cortisol/cortisone ratio (a surrogate marker for 11β-HSD2 activity) mediated those relationships. Urinary exosomes were quantified for sodium transporter/channel expression and interrogated against SBP index. Results Eighteen patients met the study criteria, nine developed transient idiopathic hypertension at a postmenstrual age of 40.6 ± 3.4 weeks. The presence of urinary DEHP metabolites was associated with prior IV and respiratory tubing DEHP exposures ( p < 0.05). Both IV and respiratory DEHP exposures were greater in hypertensive infants ( p < 0.05). SBP index was related to DEHP exposure from IV fluid ( p = 0.018), but not respiratory DEHP. Urinary cortisol/cortisone ratio was related to IV DEHP and SBP index ( p < 0.05). Sodium transporter/channel expression was also related to SBP index ( p < 0.05). Conclusions Increased blood pressure and hypertension in premature infants are associated with postnatal DEHP exposure. The mechanism of action appears to be activation of the MR through inhibition of 11β-HSD2. Electronic supplementary material The online version of this article (10.1007/s00467-019-04244-4) contains supplementary material, which is available to authorized users.

Our data support the current American Academy of Pediatrics recommendations that all infants who are born at <37 weeks' gestation, including those who are admitted to level I community hospitals, be observed for respiratory instability and secure fit in their car seats before hospital discharge. Because lowering of oxygen saturation values was seen uniformly in all newborn infants, car seats should be used only for travel, and travel should be minimized during the first months of life.

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