Nearly all medical treatments are associated with some risk. Patients with conditions that improve or resolve without treatment should not be exposed to even minor risks associated with treatments. Therefore, treatment to promote closure of the ductus arteriosus should be considered only in infants in whom early spontaneous closure will probably not occur.
Although the ductus arteriosus closes spontaneously in nearly all term infants by 3 days of age,6
the natural history of the ductus arteriosus in preterm infants, particularly extremely premature infants with lung disease, is unknown because it is so often perturbed by medical treatments. The best estimates of rates of spontaneous closure can be derived from observations of control infants in placebo‐controlled trials of timing of treatments to close the ductus arteriosus. From these studies, inferences about the rates of spontaneous closure can be drawn from observations made before the age at which treatment for the PDA is prescribed by the study, or occurs outside the confines of the study. Using this approach, Van Overmeire et al
provided an estimate of the rate of spontaneous closure of the ductus arteriosus in moderately premature infants during the first week of life.7
They investigated the efficacy of early (3 days of age) compared with late (7 days of age) treatment for PDA in 380 infants of gestational age 26–31 weeks who required ventilatory support (constant positive airway pressure or mechanical ventilation) and a fraction of inspired oxygen greater than 0.30. At 3 days of age, 67% of infants either had no PDA or had a small haemodynamically unimportant ductal shunt. One half of the remaining infants, who all had moderate to severe shunts, were randomised to receive treatment at 7 days of age if ductal patency persisted. Spontaneous closure occurred in 44% of these infants. Therefore, from these data, a rate of spontaneous closure in excess of 80% by 7 days of age can be predicted among moderately premature infants with lung disease.
Although the rate of spontaneous closure for all premature infants is high, there is a direct relationship between gestational age and closure. During the first three to four days of life, the rate of spontaneous closure is approximately 31% among infants born at 26 and 27 weeks' gestation, but it is approximately 21% at 24 and 25 weeks' gestation.8
This relationship was observed by Koch et al
who estimated that for each week of increase in gestational age above 23 weeks, the odds of spontaneous closure increased by a ratio of 1.5.9
In this study, other factors that predicted closure were antenatal steroids and the absence of major lung disease. Nemerofsky et al
reported that spontaneous ductal closure at 2 weeks of age occurred in 50% of ventilated compared with 80% of non‐ventilated very low birthweight infants.10
Of interest in both of these studies was the observation that spontaneous closure occurred in a number of infants after the first week of life.
Collectively, these observations regarding the rates of spontaneous closure narrow the population in whom early treatment (ie, in the first week of life) would logically be contemplated. Given the high rate of spontaneous closure among most premature infants, consideration of early treatment should be limited to extremely premature infants, in particular, those on respiratory support.