Aim: To assess ultrasonographically the flow pattern and the time of postnatal closure of ductus venosus in preterm infants < or = 32 weeks.
Methods: Thirty-three preterm infants < or = 32 weeks were studied within the first 1 to 5 days of life and followed every second day with ultrasound until no flow was detected either through the ductus venosus or the ductus arteriosus.
Results: The ductus venosus was closed in only 9% by day 3, in 40% by day 8 and 88% by day 18. All were closed by day 37. This is significantly later than in healthy term neonates. Closure of the ductus venosus was not significantly correlated with closure of ductus arteriosus.
Conclusion: The ductus venosus shows a delayed closure in preterm infants, with no significant correlation to the closure of the ductus arteriosus or the condition of the infant. We speculate that immaturity of the ductus venosus and possibly increased levels of dilating prostaglandins leads to a delayed obliteration of the vessel. An open ductus venosus represents a portocaval shunt and may have metabolical and pharmacological consequences.