Maternal smoking is a major risk factor for SIDS. Our aim was to investigate possible effects of maternal smoking on postnatal development of oxygen sensitivity. Fifteen healthy term neonates, born to daily smokers(median 10 cigarettes/day), and 16 controls matched by gender and maternal age were studied at 1, 3, and 10 days and 10 weeks postnatally. During natural sleep, repeated 15-second challenges with 100% O2 and 15% O2 were presented in a randomised sequence through a lightweight mask. Breath-by-breath total ventilation was calculated from strain-gauge respiratory trace recordings.

Selecting quiet sleep only, 101 experimental runs with a median of 6 challenges of each kind were analysed. For each run, the ventilatory response to hyperoxia and hypoxia was calculated as the normalised, coherently averaged response. A gamma function was fitted, yielding parameters that were further analysed with a general mixed model of variance.

Hyperoxia decreased ventilation by 7% at d 1, 13% at d 3, 17% at d 10, and 22% at wk 10. A 4% overshoot in ventilation followed. Time to response decreased with development. Hypoxia increased ventilation by 1% at d 1, increasing to 5% at wk 10. We have shown that oxygen sensitivity continues to develop over several weeks postnatally. No obvious effects of maternal smoking were detected.