Aims: To quantify the incidence of ventricular septal defect in "low-risk" neonates; and to define any associated risk factors.
Methods: One hundred and seventy three patients with ventricular septal defects from a scanned population of 3971 clinically normal neonates were compared with scanned controls, considered to be clinically normal. A subset of the group with defects was compared with normal infants delivered over the same period, to identify any seasonal variation.
Results: Ventricular septal defects were detected in 4.36 % of the "scanned" group (173 out of 3971). Ten had perimembranous defects and the remainder apical or muscular lesions. Eleven neonates had multiple defects. The incidence of ventricular septal defect was independent of most tested risk factors. There were significantly more girls in the group with defects compared with the controls (p = 0.004). The defects group also contained fewer infants born during summer months (p = 0.04).
Conclusions: The incidence of ventricular septal defects was much higher than might be expected, given that "high risk infants" were excluded. The observations that gender and season of birth affect the rate suggest that both genetic and environmental factors may be involved in the aetiology.