Aim: Delay>24 h of age in neonates' first voiding attracts attention, although the phenomenon is usually benign. Earlier studies indicate that stress increases the infant's arginine vasopressin (AVP) and aldosterone secretion during birth. Our aim was to seek predictors of delayed first voiding and indirect evidence of AVP effect behind this phenomenon.
Methods: The study population comprised 20 normal-term newborns whose first voiding was delayed>24 h of age (cases), and 19 age-matched control infants who voided for the first time at <24 h of age (controls). The first urine was collected and osmolality (U-Osm) and sodium content (U-Na) measured.
Results: The median of U-osm in cases was 432.50 (284-519) and in controls 337.50 (169-497) mOsm/L (p=0.005), and U-Na 21.50 (9-241) and 40.00 (13-226) mmol/L (p=0.001), respectively. Cases were more frequently born to primiparous mothers than controls (70% vs. 21%, p=0.004). Duration of labour was longer in cases than controls, first stage 10.5 h (3.92-20.50 h) versus 5.7 h (1.17-16.00 h) (p=0.045) and second stage 0.42 h (0.08-1.25 h) versus 0.17 h (0.08-0.92 h) (p=0.015). All seven (35%) abnormal cardiotocographies were recorded with cases (p=0.008).
Conclusions: Delayed voiding appears to be related to a prolonged and stressful birth. Laboratory findings in the first urine suggest increased AVP and aldosterone secretion in such cases.